Taken from "Nebraska Geographic Information Systems Steering Committee -
Gis Technical Standards" December 15, 1993, version.
Chapter 1. Introduction
A geographic information system (GIS) is a computer based system capable of processing
data describing locations on the earth's surface. More formally, a GIS system allows users to
efficiently capture, manage, manipulate, analyze, and display geographically referenced and
associated attribute data. GIS technology assists in integrating information in a way that helps
us understand and address some of the most pressing problems we face today -- deforestation,
acid rain, rapid urbanization, natural resource management, demographics, spread of disease,
fires, and floods, to name a few. It provides a basis for making timely and intelligent
decisions by helping us to organize data about these problems and to understand their spatial
relationships.
Geographic information system has multidisciplinary applications. Natural resources,
geographic, medical, sociological, military, and earth science activities among others require
extensive spatial data analysis. Spatial data sets are frequently heterogeneous, having data
elements such as soils, land use, streams, roads, and population statistics, and are often
comprised of data sources with different scales, coordinate systems, and collection agencies.
The variety of possible GIS applications and users, and the constant evolution of GIS
technology makes it impractical and inappropriate to generate strict criteria for GIS
implementation. However, for the same reasons, compatibility and standardization of GIS
systems becomes critical to provide conceptual integrity, data sharing, and foresight into the
future.
This technical document describes the applicable standards and recommendations for a
geographic information system in relation to the required GIS functionality. It can help the
managers and decision makers analyze their GIS requirements, evaluate a GIS system based on
those requirements, use it as a guideline for implementation and procurement of a GIS
computer system, and avoid potential incompatibilities and inoperabilities.
The document identifies current standards from the GIS developers' perspective and then
discusses GIS elements from the users' perspective -- GIS software functions, hardware
components, networking protocols, spatial data transfer standard, data capture standards, and
cartographic production guidelines. Due to the evolving nature of GIS and computer
technology, this document with refinements will also evolve to stay current with the state of
the art.
The reader is urged to perform a user requirement analysis -- reviewing the
traditional methods, identifying GIS capabilities to meet the same requirement, and the
possibilities of improving current capabilities of their organization. After a
comprehensive assessment of the analytical capabilities and products required by
potential users of GIS, the requirements can then be matched with the software functions
and the hardware elements described in this document. The reader can then review
various GIS software products based on the software functions and the hardware
components supported and perform a cost/benefit analysis. The selection of a GIS
software also dictates the minimum and recommended hardware platforms. In this
document, effort has been made to categorize and relate the software functionality with
the hardware requirements. However, the software vendor's recommendations and the
experiences of other users using the same software should also be considered when
making a decision about appropriate GIS hardware.
GIS Application Classes
Following is a taxonomy of GIS applications done by Michael F. Goodchild . Each
class includes brief comments on functional requirements and a summary describing the
application in terms of functionality, data volume, and access speed.
Natural Resources Management
GIS is a cost-effective means of analyzing data in support of many forestry applications
(timber yield estimations), computing soil erosion and modeling groundwater level and quality.
Three operations are particularly significant in explaining these interest in GIS applications for
natural resource management: area measurement, superimposition and analysis of maps of
different themes (e.g., soils and forest types), and the generation of buffers of specified width
around map features, such as streams.
Functionality: high -- data analysis often is complex.
Volume: not large by comparison -- few gigabytes is common.
Access speed: relatively unimportant -- much output is in report or map form.
Infrastructure Management
Organizations that maintain complex infrastructure need the ability to track and manage
installations geographically. For example, it is important for a utility company to know
service request locations to schedule its crews efficiently. "One-call" services that provide
information on underground infrastructure rely on geographical records access to answer
queries about existing facilities within range of proposed construction projects. Major
customers for infrastructure GIS include utilities, transportation departments, railroads, and
city and county engineering departments. The term AM/FM (automated mapping/facilities
management) often is used for infrastructure GIS applications.
Functionality: not high -- queries are generally "what is here?" or "where is it?"
Volume: large -- may reach hundreds of gigabytes.
Access speed: fast -- prompt query response is required.
Land Information Systems
Land information systems maintain data on individual ownership parcels and associated
attributes relevant to assessment and taxation. The term "multipurpose cadastre" refers to a
parcel-level database used to support a wider array of applications, such as infrastructure
management.
Functionality: not large -- queries are generally limited to attribute retrievals, and the database
also is used for simple mapping.
Volume: large -- may reach hundreds of gigabytes.
Access speed: fast -- prompt query response is required.
Vehicle Routing and Scheduling
The U.S. Census Bureau's TIGER database has led to renewed interest in using GIS to
track vehicles; plan services, such as garbage collection; and even dispatch taxicabs. All of
these applications rely on a simplified representation of a route network. Vehicle navigation
aids, for example, can display a continuously updated route map.
Functionality: not high -- limited to a few simple commands.
Volume: not large -- the entire U.S. street network numbers in the tens of gigabytes.
Access speed: fast -- prompt query response is required.
Marketing and Retailing
Location is important in determining the success or failure of a retail establishment, so it
is not surprising that geographical factors play a significant role in retail analysis. Key
functions include geocoding, the ability to generate coordinate locations from street addresses
and find them on a map; points in polygon operations to identify the reporting zone (e.g., ZIP
or county) containing a customer's location; and polygon overlay to transfer estimates of
population counts between two sets of incompatible reporting zones. Similar functions now
are being used in crime analysis and in epidemiology to tract disease patterns.
Functionality: high -- many kinds of questions may be answered.
Volume: small -- projects rarely exceed 100 MB.
Access speed: relatively unimportant -- fast response is not essential.
Redistricting
The redistricting mandated in the wake of the 1990 Census is creating interest in GIS use
for redrawing political boundaries and associated mapping. Redistricting has been an active
GIS application for some time in other areas, particularly schools and sales territories.
Functionality: high -- geocoding, dissolving boundaries, merging areas, etc.
Volume: small.
Access speed: relatively unimportant -- fast response is not essential.
Each of these application areas has specialized GIS vendors, although a few vendors
offer products across the entire application range. Specialized vendors only offer the
functionality needed in that particular application, whereas general vendors must support every
function. Bad choices often result when systems are acquired for wrong type of application.
GIS is a confusing field, particularly given the striking variety of available products.
Checklists of GIS functions provide helpful ways of navigating through the junge, but obscure
many of the important issues. For example, a simple "yes" to the question "will your GIS do
overlay?" is not very helpful to someone looking for a GIS, because "overlay" can mean so
many different things, from simple graphic superimposition through windowing to full-blown
intersection of layers of polygons. All GISs can probably do something called "overlay" but
some do more than others.
Base Reference Layers
(Obj 5, Task 2 - Identify and produce GIS base reference layers.)
Commonly used base reference layers in GIS are listed below:
* Digital Orthophotos
* Topographic
* Cadastral
* Zoning
* Geodetic Control
* Digital Elevation Model
* Monuments, Geodetic references
* GPS Controls
* Photoidentifiable Ground Controls
* Digital Line Graphs
* Hypsography (Contours), terrain
* Hydrography (Streams, Canala, Water bodies)
* Ground Transportation (Roads, Railroads, Trails)
* Political Boundaries
* Public Land Survey
* Utilities
* Drainage/Watersheds
* Land Use/ Land Cover
* Soil Surveys
* Wetlands
* Flood Plains
* Cultural and Demographics
* Geologic
* Vegetation and Non vegetation
* Socio-Economics
* Wild life
Chapter 2. GIS Elements
(Obj. 1 Task 3 - Identify the most probable and practicable range of software.)
GIS Software Functions
Range of GIS software
GIS serves as an umbrella for various types of integrated software packages. The basis
of a GIS software is the integration of spatial structure, topology, attribute manipulation, and
interactive database management. Every GIS software allows input/output, simple query and
editing capabilities to their data bases through a user friendly user interface. Advanced GIS
software also provide the facility to generate customized GIS applications.
Any software with the functionality of spatial modeling, spatial analysis, geo statistics,
automated mapping (AM), facility management (FM), urban or landscape design, decision
support, earth image processing, remote sensing, expert system, vision system, data
conversion, data integration, and document processing fits under the umbrella of GIS.
The GIS data structures could be raster (grid), topological vector, non-topological vector,
object vector, triangular irregular network (TIN), and 3-dimensional topology.
GIS packages support most coordinate systems and map projections. They can convert
between coordinate systems and between map projections.
Advanced GIS software allow spatial data to be imported and exported in various raster
and vector formats. Some also allow raster-vector integration by providing functions to
convert a raster image to a vector coverage and vice versa. They also permit vector coverages
to be registered and displayed over a raster image.
Data Management is a key feature of GIS. GIS software provide their own internal
relational database management and may also interface to popular external database managers
such as DB2, dBASE, DS, FoxBase, IMS, INFO, Informix, Ingres, Oracle, OS/2 EE
Database Manager, RBase, Rdb, Sybase, and SQL.
Data Analysis capabilities can determine the power of a GIS package. Under data
analysis, one can measure straight line distance, distance along an arc, area, and frequency.
The database can be queried by cursor input, by coordinate input, or by entering a Boolean
combination of attributes (eg. WellType = 'Municipal' OR WellType = 'Industrial'). One
can generate buffers around points, around arcs, around areas/ polygons, or some weighted
function of attributes. The data analysis can be subdivided into map analysis, surface analysis,
polygon operations, digital image analysis, and other miscellaneous functions.
The main map analysis functions allow recoding or reclassification, overlaying more than
two layers simultaneously, averaging cell values between layers, finding minimum/maximum
cell value between layers, logical combination of layers, algebraic operations on maps, local
neighborhood operations, identification of contiguous zones of equal values, and the shape
characteristics (fragmentation, narrowness).
The surface analysis includes determination of slope angle and compass aspect,
interpolation of elevation at any point, generation of line of sight/viewshed for any point, for
arcs or areas; and at user specified intervals.
Through network analysis, one can determine the shortest path along network,
accumulation of attribute values along network, perform spatial adjacency search, nearest
neighbor search, and address matching (interactive and batch mode) needs.
The polygon operations include polygon overlay, point in polygon, line in polygon,
merge/dissolve on basis of attribute, and rubbersheeting.
The digital image analysis allows radiometric corrections, sensor corrections (line
drop-outs, stripping), merging of data sets of varying resolutions, geometric corrections
(image registration/rectification), high pass/low pass filtering, user definable filters, contrast
stretch, color domain conversions, density slicing, histogram, histogram equalization,
mosaicing, principal components analysis, and band ratios.
Other miscellaneous operations include Thiessen/Voronoi tessellation, boolean
combinations of multiple maps, cross-tabulation, statistical reports, summary tables, random
sampling, and proximity ("spread") analysis.
Advanced GIS software packages may use artificial intelligence techniques in expert
systems for pattern recognition and expert systems.
GIS packages come with many user interfaces such as command language, menus (lists,
pop-up, pull-down), icons, and macros, utilizing standard windowing environment (Windows
3.1, OS/2 Presentation manager, OSF/Motif, Open Look, Environ V, X-Windows etc.).
Some even provide dual screen and multiuser capability. Advanced GIS software also support
user customizable menus, user generated macros, and online help.
The data display features permit multiple maps on single plot, shaded relief, wireframe,
thematic layer drape, animation, user definable georeference grids, cartographic elements
(scale, title, north arrow), annotation text with the facility of changing font, text size, angle,
and text alignment along irregular feature. Screen shots or images can be stored for later
display.
Checklist of GIS Software Functions
User Interfaces
___Command driven interface with___ without___ prompt and answer interface with default answers.
___Capability for pull-down or pop-up menus.
___Interactive command language interface.
___Ability to use command abbreviation (aliases).
___Allow for building of macros, shell scripts, or batch files to automatically execute complex functions from an
aggregate of simpler individual functions.
___Online help screens to summarize commands available___, and command syntax, function, and limitations for
individual commands___ or groups of commands___.
___Online___ or draft___ users manual___ and tutorials___.
___An undo command to retract previous entry.
___A recall command to restore previous entry.
___User-friendly error messages.
___Soft error recovery.
___Password access protection.
Data Base Management
General
___Facility for entering data quality information both spatial___and attribute___ data base, including: lineage___,
positional accuracy___, logical consistency___, and completeness___.
___Facility for tracking data base transactions.
___Support sequential, direct, and keyed access to data files.
___Data dictionary for defining file contents and format.
___Direct access to specific features in addition to sequential file access.
___Allow sorting of tabular or graphic files by attribute or spatial data field.
___Calculate values of new fields using arithmetic expressions or table look-up in related files.
___Capability to relate data files by shared fields and treat resultant collection as a unit for all tabular processing
functions including data entry and report generation.
___Capability to set read___, write___, access_ authorities on both spatial___ and attribute___ data bases.
___Provide ability to create, store, retrieve and generate standard reports.
___Provide the following tabular formatting capabilities: line breaks on specified fields___, page breaks___,
calculation of totals___ and subtotals___, specification of page___ and column___headings, multiple line
displays from single records.
Spatial Data Base Components
___Provision for organizing spatial files by location___, project___, theme___, and map unit___.
___Provision for multiple access___ to permanent data files, but only authorized user ability to modify data base.
___Provision for full add, delete, modify of user-created work files, by and only by the user.
___Capability to automatically catalog or index all data in the data base, including data quality___, location___,
and date last maintained___.
___Generation of status reports on content and condition of the data base.
___Capability to add data files without regard to size, or scale.
Data Base Creation
Digitizing
Methods
___Manually digitized two-dimensional point & line data.
___Manually digitized two-dimensional full polygon data.
___Manually digitized two-dimensional arc/node polygon data.
___Photogrammetrically digitized three-dimensional point, line, and polygon data.
___Manually encoded cellular data.
___Scanned map data.
___Scanned photographic data.
Tagging
___Assign feature names or codes which may be pointers to feature attributes while digitizing___ or as a separate
process___.
Keyboard entry___ Numeric___ Field length___
Menu pad entry___ Text___ String length___
Cursor pad entry___
___Facility for setting initial default values and duplicating previous entries.
Assigning Topology
___Arc pointers to areas Automatic___ Manual___.
___Arc pointers to nodes Automatic___ Manual___.
___Node pointers to arcs Automatic___ Manual___.
___Node pointers to areas Automatic___ Manual___.
___Area pointers to arcs Automatic___ Manual___.
___Area pointers to nodes Automatic___ Manual___.
___Automatic___ manual___ polygon assembly from arcs.
___Automatic___ manual___ identification/linking of complex polygons (for example, polygons with one or more
inner rings).
___Automatic snapping of line end points to nodes while digitizing___ or in batch___mode.
___Automatic polygon closure.
___Automatic polygon centroid calculation___ or manual digitizing of centroids___.
Attributes
___Allow for interactive___ or batch___ entry of multiple attributes.
___Allow attributes to be associated with features by feature name___ or by digitized coordinate___ (for example,
interior polygon coordinate).
___Allow for automatic___ manual___ insertion of calculated area___ perimeter___ length___ statistics as
attributes.
Error Detection and Editing
Raster or Vector Data
___Automatic topologic error checking, graphic display of errors, and facility for interactive correction.
___Format checking___ range checking___ value checking___ on vector___ coordinate data or raster___ pixel
data during digitizing___ or in batch___ mode.
___Interactive insertion___ deletion___ changing___ moving___ of vector___ features or raster___ pixels by
feature___ or groups___ of features.
___Automatic checking for overshoots or undershoots at line intersections during digitizing___ or in batch
mode___ and correction by redigitizing___ or automatic clipping/joining___.
Attributes and Features Names/Codes
___Interactive insertion___ deletion___ changing___ moving___ of feature names or codes.
___Checking for feature names or codes that are missing.
___Checking for illegal names/codes while digitizing___ or in batch___ mode.
___Entry level___ or batch___ checking for illegal attribute values or combinations of attribute values.
___Query select function for updating groups of graphic___ feature name___ or attribute ___ records.
Import/Export
___Ablility to import the following data-set formats:
MOSS___ MAPS___ AMS___ SAGIS___ GRASS___ ODYSSEY___
USGS DLG (Standard)___ USGS DLG(Optional)___ USGS DEM___
USGS DTM___ GIRAS___ SCS GEF___ USCB DIME___
USCB TIGER/LINE___ USCB TIGER/DATA BASE___ STDS___
FEMA/IEMIS DBMS___ DIGITAL IMAGERY___
OTHER___ OTHER___ OTHER___
___Ability to export the following data-set formats:
MOSS___ MAPS___ AMS___ SAGIS___ GRASS___ ODYSSEY___
USGS DLG (Standard)___ USGS DLG(Optional)___ USGS DEM___
USGS DTM___ GIRAS___ SCS GEF___ USCB DIME___
USCB TIGER/LINE___ USCB TIGER/DATA BASE___ STDS___
FEMA/IEMIS DBMS___ DIGITAL IMAGERY___
OTHER___ OTHER___ OTHER___
Data Manipulation and Analysis
Retrieval
___Selection of a splecific data category.
___Selection of spatial___ or attribute___ data by rectangular___ circular___ or polygonal___ graphic windows.
___Selection of spatial___ or attribute___ data by area masks defined from interactively screen digitized areas___
or redefined-reclassified data categories___.
___Selection of spatial___ or attribute___ data by feature name___ or groups of names___.
___Selection of spatial data by Boolean retrievals on attributes.
___Selection of spatial___ or attributes___ data by graphic hooks (for example, digitized point).
___Browsing either spatial___ or attribute___ data bases.
Restructuring
___Data conversion from raster to vector___ and vector to raster, with user selectable___ priority for point, linear,
or areal features.
___Interactive___ or automatic___ joining of geometrically adjacent data resolving gaps/overlaps within default or
user-specific tolerances.
___Compress___ or decompress___ raster data to run length___ or quad tree___ encoded data and reverse___.
___Modify raster cell size through resampling.
___Reduction of unnecessary coordinate detail (weeding) while retaining corner points, general sinuosity, and
shape.
___Smoothing of line data to recover general sinuosity and shape.
___Generate contours from either random___ or gridded___ (raster) Z-value data points, and conversely generate
gridded Z-value data points from contour data___.
___Generate a triangulated irregular network form random___ or gridded___ (raster) Z-value data points or from
contour data___.
___Generate gridded___ data or contour___ data from a triangulated irregular network.
___Constrain contour generation by specifying barriers___ (for example, fault lines).
___Provision for the following coordinate geometry capabilities: protraction of parallel lines___ curves___ and
features___; create equal line___ and arc segments; tangent___ and exterior tangent___ lines.
Transformation
___Mathematical adjustment of vector___ or raster___ data to control points using rotation/translation/scale in X
and Y___ (4- parameter), rotation/translation/scale in X or Y___ (6-parameter), local area rubbersheeting___,
polynomials___, or some other___ type of least-squares adjustment.
___Recovery of geographic ground coordinates from digitized photographic data using single-photo
resection/intersection techniques together with digital elevation data___ or strips of stereo photographs using
analog___ or analytical___ plotters.
___Transformation of ground survey bearing and distance data to geographic coordinates using least-squares
adjustment of traverse data to known ground control.
___Radiometric calibration of remotely sensed digital image data___ or scanned photographs___.
___Rescaling of raster data values (for example, contrast stretching).
___Map projection conversions similar to those available in the USGS/NOAA General Cartographic
Transformation Package (GCTP).
___Albers Conical Equal-Area.
___Azimuthal Equidistant.
___Equidistant Conic.
___Equirectangular.
___General Vertical Near-Side Perspective.
___Geographic latitude and longitude.
___Gnomonic.
___Lambert Azimuthal Equal-Area.
___Lambert Conformal Conic.
___Mercator.
___Miller Cylindrical.
___Oblique Mercator (Hotline).
___Orthographic.
___Polar Sterographic.
___Polyconic.
___Sinusoidal.
___State Plane.
___Stereographic.
___Transverse Mercator.
___Universal Transverse Mercator.
___Van Der Grinten I.
Vector or Raster Overlay
___Boolean AND___, OR___, XOR___, NOT___ overlay operators for vector data: polygon in polygon___, point
in polygon___, point in line___, line in polygon___.
___Boolean AND___, OR___, XOR___, NOT___ overlay operators for raster cell data: polygon in polygon___,
point in polygon___, point in line___, line in polygon___.
___Ability to weight features within a data category___ or data categories___ during the overlay process.
___Ability to superimpose one data category on another with replacement.
___Ability to automatically___ or manually___ merge attribute information resulting from a graphical composing
process, (for example, Polygon C, a result of A (corn) and B (soil X) has concatenated attribute corn/soilX).
Raster Cell Operations
___Ability to assign binary (1/0)____, discrete (0-32768)___ or real continuous___ data values to cells in a raster
data set.
___Ability to perform the following mathematical operations on two or more raster data categories: add___,
subtract___, mulitply___, divide___, minimum___, maximum___.
___Ability to perform the following mathematical operations on a single raster data category: exponentiate___,
logarithm___, natural logarithm___, absolute value___, sine___, cosine___, tangent___, arcsine___,
arccosine___, arctangent___.
___Ability to replace cell values with a new value reflecting some mathematical combination of neighborhood cell
values: average___, maximum___, minimum___, total___, most frequent___, least frequent___, mean
deviation___, standard deviation___, other___.
___Supervised___, unsupervised___ clustering capability.
General
___Ability to specify distance buffers from point, line, or polygonfeatures.
___Determine alternative and optimum paths through a network.
___Automatically identify drainage networks___, watersheds___ and viewsheds___.
___Perform cut/fill___ and profile___ analysis on terrain data.
___Generate slope, aspect, and sun intensity data categories.
___Compute azimuth___, bearings___, and geographic point locations___.
___Define, open and close, and adjust traverses.
Statistics
___Calculate areas___, perimeters___, lengths___, and volumes___.
___Calculate acreage___ and percent of total___ for cross tabulations of mutual occurrences between two data
categories.
___Compute the following descriptive statistics from tabular data: means___, medians___, quartiles___,
percentiles___, range___, mid-range___, standard deviation___.
___Conduct the following statistical analysis on tabular data: correlation___, regression___, analysis of
variance___, factor analysis___, discriminate analysis___, contingency tables___.
___Support the following testing:
T-test___, chi-square___, Mann-Whitney___, Runs___.
___Calculation of confidence intervals___ and Wilcoxon intervals___.
Data Display and Product Generation
General
___Generate graphic displays on graphic terminals___, digital plotters___, inkjet printers___, color ribbon
printers___, matrix printers___, laser printers___, electrostatic printers___, character printers___, film
recorders___.
___Display source raster___ or vector___ files on either raster___ or vector___ display devices.
___Generate maps via copy of the display screen.
___Generate maps that are larger than the physical dimensions of the output display device, that can then be
mosaicked.
___Generate three-dimensional orthographic___ and two-point perspective view plots___ of gridded surfaces___
or other Z-value data categories___.
___Compose displays interactively___ or use default ___ map composition layouts.
___Capability to specify the location___, size___, scale___, and orientation___ of multiple___ viewports on a
single display.
___Ability to display point, line and polygon data sets.
___Ability to display map neat lines___, grid lines___, tick marks___ in a latitude/longitude___, state plane___ or
UTM___ coordinate reference, with annotation___ at specified scale___.
___Ability to select point symbols___, line types___, area fill patterns___ and character fonts___ from existing
tables.
Map and Map Feature Annotation
___Facility for creating, naming, storing, retrieving and interactively positioning: map tittles___, legends___,
bar___ or text___ scales, north/south arrows___, single-line or blocked multi-line text strings___.
___Ability to specify font type___, case___ character size___, color___ and string orientation___ for all text
entries.
___Ability to automatically position___ text entries at prespecified point locations (for example, polygon
centroids), supplemented with the capability to interactively move___ or rubberband___ respective entries.
___Facility for creating, naming, storing and selecting default point symbols___, line types___ and area-fill
patterns___.
___Ability to assign point symbol___, line type___, line width___, area-fill pattern___ and color___ to graphic
features by specifying a feature name___ or group of names___, feature display color or group display
colors___, attribute or group of attributes___ or interactively selecting features with a cursor___.
___Ability to cross-hatch fill areas by specifying hatch color___, line type___, rotation angle___ and distance
interval.
GIS Hardware Components
The hardware employed by GIS is needed to support GIS software functions. It includes
the computer system environment, data capture/input devices, processing devices, interactive
display and edit devices, external storage devices, and output devices. Most devices are
available with a general purpose computer system configuration. The only functions requiring
somewhat specialized equipment are data capture (digitizing) and data display (graphics and
color output).
* The data entry or input devices range from manual digitizing tables/tablets, 3-D analytical
stereocompiler, flatbed and drum scanners, global positioning systems (GPS),
photogrammetric stations, mouse, and keyboard.
* The processing devices comprise of a uni or multi processor computer system and its I/O
subsystem processors. The amount of memory (cache, RAM) also affects the processing
speed of the computer system.
* The interactive display and editing devices include the monitors and graphic terminals
using vector refresh, storage tube, or raster refresh display technology, alphanumeric
keyboards, mouse, and digitizing tables/tablets.
* The external storage devices include disk storage (fixed, removable, floppy), magnetic
tapes (reel to reel, cartridge), and optical storage (CD-ROM, laser disk, optical disk).
* The output devices supported by GIS packages include pen plotter, ink jet plotter,
electrostatic plotter, film recorder, laser printer, dot matrix printer, and digital typesetters.
Communications and Networks
(Obj. 1 Task 4 - Identify the most probable and practicable range of communication
protocols)
A computer network is a collection of computers connected together by both hardware
and software. The main reason to connect computers via a network is to facilitate the sharing
of resources. For example, a single networked plotter can service many host computers while
being physically connected to only one of them. Terminal ports can be shared via a terminal
server, disks via a distributed file system, and tape drives via commands that operate both
locally and remotely. Software systems exist that facilitate the use of a remote machine's
CPU.
Data and resource sharing is an essential element to implement a cost effective GIS
making networks a logical extension to standalone computer systems. Networks require both
physical connectivity and standard communication protocols. Physical connectivity is achieved
through local area cabling or leased telephone lines and communication satellites for wide area
high speed networks.
Communication protocols
Standard communication protocols for networking include OSI, TCP/IP, IPX, Adaptive
SRT, X.25, PITM, XNS, DECnet, Source Routing Bridge, Spanning Tree Bridge, Apollo
Domain, Apple Talk, SDLC Relay, and Frame Relay.
Internet
The TCP/IP (Transmission Control Protocol/Internet Protocol) is the communication
protocol of Internet. The INTERNET is a "network of networks" (a large collection of
networks) where users of any one network can use the services of any of the other networks.
Internet network is a concatenation of many university campuses, states, regional, national and
international networks, such as the ARPANET NSFNET, JUNET, NORDNET, ONet, etc.
They all share a common addressing scheme called the Internet number or the Internet address.
The INTERNET started with the ARPANET which now includes NSFNET, NYSERNET,
MIDnet and thousands of other networks.
Once you have access to Internet, you have access to all the resources that you are
authorized to use on your own Internet host, or any of the other Internet hosts that offers
publicly accessible information. The Internet network provides interactive computing, file
transfer and electronic mail, and gives you the ability to move information between these
hosts. The actual connection between the various networks take a variety of forms. The most
prevalent for Internet links are the 56K leased lines (dedicated telephone) and T1 links (special
telephone lines with 1.44Mbps connections). Also installed are T3 links acting as backbones
between major locations to carry a massive load of 45Mbps traffic. The INTERNET currently
has over 200,000 hosts worldwide.
Nebraska and six other adjoining states including South Dakota, Iowa, Kansas, Missouri,
Oklahoma and Arkansas, are part of the MIDNET which is then linked to the NSFNET. The
NSFNET currently links over 700 higher education and corporate research networks. Today,
the Internet (including NSFNET and MIDNET) has become an integral part of the nation's
infrastructure.
Chapter 3. Recommended Specifications for GIS Elements
Typically, a GIS application determines the GIS software functionality which in turn
induces the hardware and networking requirements to efficiently implement that application.
An amazing array of products are available under the general label "GIS," including packages
for all kinds of computing platforms and all of the major operating systems. It appears that
every new GIS application spawns a new collection of products, each with its own unique
approach to representing and handling geographic data.
With this diversity, how can an inexperienced GIS user make an intelligent set of
choices? What are the key characteristics that distinguish one GIS from another? Are there
useful ways of grouping GIS products? A taxonomy of GIS, perhaps.
In a sense, all GIS products serve the same goal: presenting information in a way that
supports spatial decision making. But if one looks at the GISs that have been built for decision
making in different applications, there are distinct differences. A helpful approach is to look
at a GIS's data types and its architecture, because these ultimately determine what can be done
with the system.
GIS Software
(Obj. 2 Task 2 - Software - acquisition, maintenance, and service)
The minimum requirement of a GIS software is based on the desired level of GIS
functionality. For example, users interested in implementing only a GIS front end for data
access and display do not require a full GIS capability. However, for a general purpose GIS
implementation, it is advisable to go with a platform-independent, full featured, modular, and
well supported software such as ARC/INFO. from Environmental Systems Research Institute,
Redlands, California; MGE Segment Manager from Intergraph Corp., Huntsville, Alabama;
GEO/SQL from Generation 5 Technology, Edmonton, Canada; Graphics Systems Design from
McDonnell Douglas, St. Louis, Missouri; GRASS from GRASS Information Center,
Champaign, Illinois; ERDAS from ERDAS Inc., Atlanta, Georgia; SPANS from TYDAC
Technologies Corp., Arlington, Virginia; and various others. Functionalities and general
information about various GIS software packages is listed in the 1991-92 International GIS
Sourcebook.
The compatibility of the GIS platform and software with other organizations in the area
is another important consideration for choice of a GIS system to coordinate information
sharing, GIS training and implementation. For a new GIS system, initial training classes
offered by software vendors or local universities makes it easy to implement the system
successfully. To keep up with the latest updates and software revisions, it is useful to maintain
an annual software contracts with the software vendors.
All advanced GIS software packages provide tools and facilities for data automation, map
production, and spatial data analysis. As new algorithms and techniques are invented, these
software try to incorporate new tools and features in their upcoming software releases. The
needs of GIS users also tend to diversify with experience and the users expect updated versions
of the software with time. There is an ongoing relationship between the GIS software
developers and its user community that dictates the directions of the software upgrades. A
software with a large user support will thus try to envelop most user demands whereas the
software with few users will end up focusing on limited domains.
Full featured GIS software normally follow a modular approach where the software is
divided into independent modules. Each module contains a set of tools to support a basic
function (such as map making, data automation etc.). The users have a flexibility to purchase
only the modules that they need to execute their project.
Training support is another crucial aspect in deciding the right GIS software. Training is
made available through the vendor, the universities, and self learning workbooks. GIS
software with a large user base are able to provide many venues for training. They also
generate opportunities for GIS users to interact and share ideas worldwide through newsletters
and user conferences.
Recommendation: The GIS Steering Committee recommends that all software be
evaluated by benchmark testing using the intended platform and similar data to insure
their adequacy prior to purchase. A GIS software should meet the desired GIS
functionality (both current and anticipated), has a comprehensive set of features,
supports modularity, has an established user base, has a provision for local training and
technical assistance through telephones and electronic forums, and facilitates the sharing
of information.
Hardware Platforms
(Obj. 1 Task 2 - Identify most probable and practical range of platforms)
GIS software is available for all types of hardware platforms and is based on a variety of
operating systems such as UNIX, DOS, VMS, OS/2, Primos, AOS/VS, MVS, VM/CMS, and
others. A GIS package with limited functionality can run on an inexpensive PC platform with
640K main memory and a 14" color monitor (640 x 480 resolution, 16 colors) in the DOS
environment. For many GIS applications such as GIS front ends for data viewing and
plotting, the GIS package with limited functionality may be adequate. However, full featured
GIS packages require workstations as their primary hardware platforms with at least 16 MB of
main memory, 1Gigabyte of secondary storage (hard disk), and recommend large graphics
monitors (19" and above) with the capability of 1024 x 768 resolution and 256 colors.
Intergraph, SUN, DEC, IBM, HP, Data General, and SGI are some of the major vendors in
the workstation market. Certain GIS software can also run on mainframe computers such as
IBM, PDP and VAX systems. As a rule most workstations running GIS applications operate
in the UNIX environment. Many workstation vendors are also heading for new operating
systems such as Windows NT and accordingly, GIS software developers are also considering
porting their software to run under Windows NT.
(Obj. 2 Task 1 - Hardware - acquisition, maintenance, and service)
The minimum specification of hardware depends on the software chosen for
implementing GIS. A PC based GIS software will generally require at least a 80386 CPU
(Central Processing Unit) with 4Mb of RAM, 14 " Super VGA color monitor supporting
minimum of 640 x 480 resolution and 16 colors, a math co-processor, and a parallel port.
Advanced GIS software show satisfactory performance only on workstations based on a high
end CPU and graphics monitor (19", 1024 x 768 resolution, 256 colors) with 32 MB of RAM,
1 GigaByte hard disk space and a backup media such as an 8mm tape. However, a
workstation also acting as a network file server needs top of line CPU with at least 64MB of
RAM and enough hard disk space to support all users. The client workstations in that network
could be low end workstations or PCs with adequately sized monitors connected to the network
running software that transforms them into an Xterminal (a graphical terminal running X-
windows).
The PC platforms are generally stand-alone, do not need much maintenance, and
technical support is available from many local PC vendors. Workstations, however, require
initial technical support in order to run the operating system smoothly. Thereafter, regular
system administration is required especially in a multiuser networking environment. For a
new GIS systems, a minimum of 1 year technical support and service maintenance is
recommended.
GIS software puts a high demand on the CPU processing and graphic capabilities of the
GIS hardware. The demand multiplies if the software is run in a multiuser, multitasking
environment. Moreover, these software are constantly expanding in their capabilities with the
inherent assumption that the computer hardware will grow with them. Upgradability, thus,
becomes an important criteria when selecting the appropriate hardware for the GIS software.
However, one must consider the stakes involved in upgrading a piece of hardware -- is
upgradability a matter of replacing few integrated chips or does it mean discarding the old
hardware and getting a new one. For instance, the only way to upgrade a small monitor to a
larger monitor is by purchasing the larger monitor. In situations like these, it is better to give
a headstart to the hardware -- go with the larger monitor.
In terms of processing power, most GIS software developers target at workstations as
their primary hardware platforms. A high end workstation is able to support the needs of GIS
software in a multiuser environment. It does not matter which workstation vendor one chooses
to run the software as long as the workstation is supported by the software developer.
However, the selection of proprietary workstation vendors may limit future selections of
hardware, software and connectivity options. Advances taking place in hardware technology
related to CPU power and performance, operating systems, and networking also have to be
considered. Many times, the GIS software developers stop releasing their software upgrades
for workstations that are based on older technology (even though they were supporting them
before) and focus their support on the workstation environments which the hardware vendors
are actively promoting as their line of hardware platforms. PCs, even with their increasing
processing speeds do not come in the category of high end workstations. Rather, they serve as
good X-terminals with the help of inexpensive X-server software and possibly act as Windows
NT clients in the future..
Another crucial aspects affecting the decision regarding GIS hardware platform is the
availability of training and the hardware vendor's reputation of maintenance and support.
Workstation environments almost always require a qualified and knowledgeable person to
maintain and administrate the system.
The databases developed during GIS projects are large and require large amount of disk
space. Increasing the disk space is a matter of adding more hard disks and can be done on a
need basis. However, one must remember that today's complex operating systems and the
workstation GIS software(s) may itself take upto 1 Gigabyte of hard disk space.
The GIS Steering Committee recommends that all platforms be evaluated by benchmark
testing using the intended software and similar data to insure their adequacy prior to
purchase. Experience with existing systems indicates that:
Recommendation 1: An entry level GIS platform requires a 486DX2 level PC with
graphics card, 32 MB RAM, 19" or larger color monitor with 1024x768 resolution, 1
Gigabyte of hard disk storage, and backup capability.
Recommendation 2: More sophisticated GIS applications requires a high performance
workstation (integer specmark over 30) supported by the GIS software with 64 MB
RAM, a large (19" or above) color monitor with a graphics card with minimal 1024x768
resolution (256 colors), a minimum of two Gigabytes of hard disk, and an 8mm data
cartridge (tape) backup media or equivalent.
Networking
(Obj. 2 Task 3 - Communication and Networks)
A GIS project can involve many concurrent users working at their individual sites and
thus require data and resource sharing. It is common to use a client server architecture for a
networked GIS environment. In a client server architecture, one (or more) high end machines
called the server(s) is (are) assigned the role of supplying all the GIS resources (data, software,
hardware accessories such as printers, plotters) to the clients on the network. The clients could
be workstations with their own processing capability or graphics terminals using the processing
power of either the network server or a workstation. This way, only one copy of the data set
and GIS application software needs to be stored with the file server and shared with all the
clients.
For a small GIS network (say upto six concurrent users), the configuration of one high
end workstation as a server with X terminal clients is the most cost effective. X terminals are
machines with the ability to run X-Window applications. Most GIS applications running on a
workstation use X-Window programming interface for displaying graphics and need machines
with X-terminal capability. Although, there are machines available that only act as X-
terminals, a PC with graphics capability can transform into an X-terminal using inexpensive
PC based X-server software. When procuring X terminals, one should consider a PC with a
good monitor running X-server software. This allows a user to run both PC based (such as
your favorite word processor) and workstation based GIS applications from the PC at the same
time. A larger network should have multiple file servers, possibly of the same type (binary
compatibility). It not only eases maintenance responsibilities but also allows sharing of GIS
software among file servers via Network File System (NFS) mechanism.
The TCP/IP (Transmission Control Protocol/Internet Protocol) is the standard
communication protocol accepted by all hardware and software vendors. For a GIS
implementation over a network, supporting TCP/IP standard would be sufficient. With the
growing popularity of Internet, it is safe to assume that every network would want to use the
Internet some day. However, one can plan ahead for this step by ensuring that the network
supports the Internet's TCP/IP protocol and has been registered with the Internet
administrators (the Network Information Center (NIC) at the Stanford Research Institute). The
Internet administrators allocate unique Internet addresses to every machine on the network
even though the network may not be connected to Internet for some time. This way, when the
network is physically connected to Internet, no network reconfiguration is required. These are
many ways to connect a network to Internet and the GIS Steering Committee can be contacted
for referral to someone knowledgeable about Internet and its connectivity procedures.
The GIS Steering Committee recommends:
Recommendation 1: That agencies and organizations without network experience should
initially limit their GIS network to six concurrent clients per file server, learn to manage
that network efficiently, and then gradually expand the network by adding more file
servers and clients as the situation warrants.
Recommendation 2: Connectivity to Internet should be strongly considered by seeking a
direct access to Internet gateway or through a local area- or wide area-connection to a
cooperating network already on the Internet to facilitate data sharing. It should be noted
that Internet connection requires TCP/IP protocol and an Internet address.
Recommendation 3: State-of-the-art telecommunications switching technologies be
accessed at the earliest opportunity. Such technologies include Frame Relay, Switched
Multimegabit Data Service (SMDS), Asynchronous Transfer Mode (ATM) for wide area
networks, and fast Ethernet, Fiber Distributed Data Interface (FDDI), ATM for local
area networks.
Chapter 7. Compatibility of GIS-related systems
Incentives and Education
(Obj 6 Task 1 - Identify potential incentives for compatibility)
In times of tight budgets anyone implementing or maintaining a GIS is interested holding
down costs. The cost (and potential savings) of a GIS system can generally be broken down
into the following four components:
* Software, including GIS, database management and application software
* Hardware, including workstations, disk drives, tape drives, plotters, scanners,
digitizers and communication hardware.
* Data, including both internally developed data and externally acquired data from
other sources.
* Personnel, including the organization's staff as well as outside assistance.
Creating a database (whether it is acquired from outside, or developed inhouse) is
generally the most expensive element of a GIS system. It typically involves 60 to 80 percent
of total funding. Because of high costs of data development, cooperation and joint efforts
among GIS database users can provide a tremendous opportunity for cost savings.
Data sharing is another important step in reducing the cost of developing the GIS data.
Generally, this requires data to be available in compatible formats over interconnected
networks. If network connectivity is not yet feasible, then GIS systems should support
compatible data transfer media (such as 8mm tape drives) to allow the transfer of data from
one system to another. In this context, however, multiple copies of data base have to be
maintained (one on each system) making it difficult to manage and update the data. Such
difficulties are eliminated through network file sharing where one copy of data set is kept at
the centralized file server over the network and is accessed by many clients. Additionally,
only one agency or organization is responsible for updating and maintenance of the data.
Although many issues like data ownership, liability, limitations, restrictions, resolution, and
quality assurance have yet to be resolved.
In some situations, under a multi-user environment, GIS software can also be shared. To
use a GIS to its fullest potential, initial training is essential. Availability of this group training
and technical support should be a consideration in the selection of the GIS software.
Data Access and Transfer Parameters
(Obj 6 Task 2 - Set parameters for assistance and access to data)
Data access and transfer require the consideration of the following parameters.
o GIS Data Format - This parameter establishes the import/export data format
supported by the two GIS systems amongst which the GIS data is to be transferred.
SDTS may become the data format acceptable by the GIS software vendors.
o Transfer Media - This describes the hardware (media) that will be used to transfer
the data between the two GIS platforms. Floppy diskettes are the universal media
supported by most platforms including PC's and workstations. The common
transfer media are:
Magnetic Tapes - 1/2" 7 track/9 track reels
Flexible Disks / Floppy Diskettes - 3 1/2", 5 1/4", 8"
Data Cartridges / Streamer Tapes
- 4 mm, 8 mm
- 1/4", 1/2"
- Bernoulli
- TK50, TK70, TZ30 Tape Cartridges
Hard Disks
Disk Packs and Disk Cartridges
Optical Disk Rewritables - 3 1/2", 5 1/4" Cartridges
CD-ROMs
Paper Tapes
Hard Cards
Highlighted items indicates more commonly used media to exchange information.
The CD ROMs are an efficient form of media when the data has to be distributed
to many GIS sites.
o Data Transfer Utility - The data transfer utility is a software (operating system
command) that allows the GIS data to be properly loaded onto the transfer media
and then unloaded from that media. It is required that compatible data transfer
utilities be used on both GIS platforms. Some common data transfer utilities under
DOS environment are the "copy", "backup" and "restore" commands. Under
UNIX environment, these utilities are "tar" and "cpio" commands. Some GIS
systems offer their own tape (read and write) utilities, but they are useful only
when moving data between similar GIS systems.
o Network Connectivity - Information can be easily exchanged between two GIS
platforms if they are connected through a network. This is usually done over the
local network or a network connected to a wide area network such as the
INTERNET.
Recommendations: The GIS Steering Committee recommends that:
1. Data access and transfer should be facilitated via statewide networks.
2. Agencies and organizations should provide their metadata to the Nebraska Library
Commission "Nebraska Online System". This facilitates knowledge about GIS data
availability and how data can be shared.
3. Agencies and organizations should utilize an on-site testing of an existing turn-key
GIS system.
4. Owners of existing systems should allow other potential users to learn about their
GIS operations.
5. Users should choose GIS software which supports Special Data Transfer Standards.
The SDTS also incorporates meta data standards which encourages appropriate use
and sharing of databases.
Chapter 8. Federal Standards from the Developers' Perspective
(Obj. 1 Task 1 - Identify current industry or existing national standards)
Although not critical for a GIS implementation, the end-user should be aware of the
hardware/software standards considered by the developers of GIS systems. The National
Computer Systems Laboratory at the National Institute of Standards and Technology (NIST)
has been developing the Applications Portability Profile (APP) for an open system
environment to define standards for integrated information systems such as GIS. In its
Application Portability Profile, NIST defines an open system as a computing environment that
delivers interoperability, portability, and scalability across heterogeneous multi-user networks.
The primary benefits of APP are:
* Less investment risk. By migrating to open systems, organizations reduce their exposure to
an uncertain market-place.
* Lower costs. Applications written on one hardware platform can run unchanged on other
systems. Time and money are saved as production and distribution costs are minimized.
* Flexibility. Users no longer are locked into a particular hardware architecture, operating
system or networking solution.
* Scalability. With a broad set of options available, organizations no longer need to make a
large, up-front investment. They can scale their open systems up or down as requirements
evolve.
Although targeted for use of the federal government for its own development of GIS systems,
the NIST has recommended APP standards as outlined in Table 1 and explained in the
following paragraphs.
Table 1 - Applications Portability Profile
OPERATING SYSTEM SERVICES
Kernel Operation -- (POSIX) FIPS 151-1, ISO 9945-1
Commands and Utilities -- IEEE P1003.4, DPIS0 9945-2
Real-time -- IEEE P1003.4
Security -- IEEE P1003.6
Systems Administration -- IEEE P1003.7
PROGRAMMING SERVICES
Languages
ADA -- FIPS 119, ISO 8652:1987 (approval without waivers)
C -- X3J11/88-002
COBOL -- FIPS 021-2, ISO 1989:1985
FORTRAN -- FIPS 069-1, ISO 1539:1980
PASCAL -- FIPS 109, ISO 7185:1983
CASE Environments and Tools
Library Support
DATA MANAGEMENT SERVICES
Data Dictionary/Directory (IRDS) -- FIPS 156
(Army Regulation 25-9 Data Standardization)
Query (SQL) -- FIPS 127, ISO 9075:1989
Reporting
DATA INTERCHANGE SERVICES
Documents
SGML -- FIPS 152, ISO 8879:1986 (CALS)
ODA/ODIF -- ISO 8613 (CALS)
Product Descriptions -- (IGES) MBSIR 88-3813
Graphics -- (CGM) FIPS 128, ISO 8632:1986
Geographic Information -- Spatial Data Transfer Standards (SDTS) FIPS 173
Meta Data
Thematic Definitions
GRAPHICS SERVICES
GKS -- FIPS 120, ISO 7942:1985 (CALS)
PHIGS -- FIPS 153, ISO 9592:1988 (CALS)
USER INTERFACE SERVICES
Client-server Operations (X Window Systems) -- X Consortium
Version 11, Release 3 (FIPS 158)
Object Definition and Management (X Window System) -- X
Consortium Version 11, Release 3
Window Management -- IEEE P1201
NETWORK SERVICES
Data Communications -- (GOSIP) - FIPS 146
Transparent File Access -- P1003.8
Remote Process Execution -- P1237
Acronyms:
CASE Computer Aided Software Engineering
CGM Computer Graphics Metafile
FIPS Federal Information Processing Standards
GKS Graphical Kernal System
GOSIP Government Open Systems Interconnection Profile
IEEE Institute of Electronics and Electrical Engineering
IGES Initial Graphic Exchange Specifications
IRDS Information Resources Dictionary
ISO International Standards Organization
ODA/ODIF Output Data Architecture/Output Data Interchange Format
PHIGS Programmer's Hierarchical Interactive Graphic System
POSIX Portable Operating System Interface for Computer Environments
SDTS Spatial Data Transfer Standards
SGML Standard Graphic Mark-up Language
SQL Structured Query Language
The APP architecture as shown below, adopted by the U.S. Army Sustaining Base Information
Services calls for separating the systems application software from the overall computing
infrastructure. This allows the applications to access computing services through a series of
standard interfaces, data formats, and protocols. By separating applications software from the
infrastructure, one can insert new computing technology as it evolves without having to rewrite
the custom applications.
Operating System Services
The APP objective is to remove any dependence on vendor specific operating system
software or hardware. The standard interface definitions should provide portability to the
operating system environment independent of the hardware platform or the applications GIS
software.
The NIST has adopted the Portable Operating System Interface for Computer
Environments (POSIX) as a national standard for the operating system services. These
standards define the functional interface between an operating system environment and the GIS
software that conform to POSIX specifications as specified in the Federal Information
Processing standards (FIPS) publication 151.
Programming Services
The APP Languages include ADA, C, COBOL, FORTRAN and PASCAL. These
languages have NIST conformance validation tests to detect the correct interpretation of the
source language by the compiler implementation. With the popularity of the UNIX operating
system environment for both workstations and super mini-hardware platforms, the C-language
is becoming a widespread de-facto standard. Currently, Computer Aided Software
Engineering (CASE) environments and tools are getting more popular in software engineering
and integration efforts. The Programmers Software Library support is another element of the
APP programming services that provides reusable code for application and system
development, and reduces the burden for configuration management. Language specific
implementations of software libraries include data input-output and string manipulation,
mathematical operations, graphics, task management, and network data communications. The
standardization of this component is important in integration of application system
development.
At this time, there is no mention of fourth generation (macro) language standards in the
GIS application domain.
Data Management Services
The GIS interface to data management services often determines the extent to which a
system is truly integrated across all data types, including spatial features and associated
attributes. The interface also establishes a client/server relationship between user workstations
and database server platforms. The use of standard interface definitions provides an effective
facility for integrating GIS software with other applications software, as well as
interoperability across database management software packages that conform to the standard
interface specifications. The NIST has chosen Structured Query Language (SQL) and
Information Resources Dictionary Systems (IRDS) as the key for conformance testing of data
management services.
The SQL is the database language for defining, accessing, updating and protecting a
relational database. IRDS is a software for managing data information. A standard data
dictionary ensures data security, transfer, maintenance and integrity.
Data Interchange Services
The APP specifies several standards for data interchange, depending on the type of data
to be exchanged. The following national and interspatial proposals are being discussed as
standards for geographic data interchange:
- Authoritative Topographic Cartographic Information System (ATKIS)
- Canadian Council on Geomatics Interchange Format (CCOGIF)
- Digital Geographic Information Exchange Standard (DIGEST)
- Digital Line Graph (DLG)
- Digital Line Graph-Enhanced (DLG-E)
- European Transfer Format (ETF)
- Geographic Data File (GDF)
- Map and Chart Data Interchange Format (MACDIF)
- Mapping Interchange Data Format (MDIF)
- National Transfer Format (NTF)
- Spatial Archive and Interchange Format (SAIF)
- Spatial Data Transfer Standard (SDTF)
- Specifications for the Exchange of Digital Hydrographic Data - 1990 (DX-90)
The Initial Graphic Exchange Specification (IGES) was selected for the interchange of
product description data. The Computer Graphics Metafile (CGM) was selected specifically
for graphics data interchange.
The Spatial Data Transfer Standards (SDTS) was selected for interchange of GIS
databases. The NIST recently adopted the SDTS as a Federal Information Processing
Standards (FIPS 173) for geographic information which takes effect in February 1993. The
federal agencies have until February 1994 to implement these data exchange and transfer
standards. The SDTS's purpose is to ensure that no data is lost during transfer. Fidelity of
the data and its relationships are preserved and there is full apprehension of the file after the
exchange.
The NIST under the guidance of Federal Geographic Data Committee (FGDC) has also
submitted a proposed draft on metadata standards for review by the spatial data user and
creator community.
The FGDC has also formed several subcommittees to develop thematic definitions, and
establish standards for base cartography, cadastral, cultural, geodetic, geologic, ground
transportation, soils, vegetation, wetlands, international boundaries, and bathymetric data.
The subcommittees draft reports are under review.
Graphic Services
Graphic interface often determines the system's portability and interoperability
characteristics. The Graphical Kernal System (GKS), and the Programmer's Hierarchical
Interactive Graphic System (PHIGS) are important standards for graphic services selected by
NIST.
The NIST GKS test provides for five classes of tests including data consistency, data
structure, error handling, operator display, and metafile tests for visual comparison between
screen outputs and reference pictures.
PHIGS tests for consistent data structures and correct graphical screen displays using
specific functions. To specifically address graphic systems performance, the Graphic
Performance Characterization (GPC) Committee comprised of major industry sponsors,
developed the Picture Level Benchmark (PLB). GPC members believe that no single
performance value, such as Dhrystone, MIPS, Linpack MFLOPS, can adequately describe the
performance characteristics of a graphic system. The ultimate GPC goal is to develop an
application-level benchmark that would determine how fast different machines run specific
user applications including graphics, windowing, input/output, and the operating system.
User Interface Services
User interface is the look and feel of a GIS system that users see and interact on their
workstation computer screens. NIST has adopted the X-window system as the APP basis for
standard user interface services. The server is the graphics display software that supports the
user interface at the workstation. The client is the application software that communicates
with the user by way of the X-protocol. This client software can be on the user's workstation
or across a network on a different computer. In fact, multiple client applications executing on
several different computers can communicate to the same user interface via the X-protocol.
This provides great flexibility in allocating application software to workstations or services on
a network and configuring overall system architecture.
NIST has a conformance test suite under development for the X-window systems. The
X-protocol is tested for compliant communications and the data object definitions for
consistency with the standard.
Network Services
The network interface is critical to linking multiple user workstations into a workgroup,
and multiple workgroups within an enterprise. Local area networking is used to link
individual user workstations into a local workgroup, usually across short distances. Linking
individuals and work groups across longer distances is accomplished with wide area
networking.
The national standard for networking is the Government Open Systems Interconnection
Profile (GOSIP). The first version of GOSIP included the X-400 message-handling system
and the File Transfer Access and management (FTAM) specification. The second version,
GOSIP2, added features for remote log-in using Virtual Terminal applications. Other GOSIP
specifications include X.44, X.25, transport, FTAM and 802.3 communications protocols.
For exact technical details on Federal Information Processing Standards (FIPS), write to:
NATIONAL TECHNICAL INFORMATION SERVICE
5285 Port Royal Road
Springfield, VA 22161
(703) 487-4650