The P-Factor is the erosion control practice factor expressed as a ratio of soil loss with contouring, strip cropping or terracing to soil loss with straight row up-and down farming. For raster data: The digitized p-factor survey data is a digital product of the unrectified aerial photographs of Nebraska. The field data was obtained by Consolidated Farms Service Agency and was digitized by the Nebraska Department of Natural Resources. It is based on 8 acre cell size and each county contains on the average 10 different p-factor symbols. For vector data: The p-factor data is a digital product of the p-factor for Nebraska. The base data was collected by the Natural Resources Conservation Service and scanned by the Nebraska Natural Resources Commission. Each county contains on the average 10 different p-factor symbols. The only county in vectorized format is Gosper.
The digitized p-factor data main purpose is being a layer in the universal soil loss equation.
For raster data: A transparent grid was placed over a county unrectified aerial photograph map by the NRCS field office employees and data transferred manually. Results were key punched and processed on an IBM mainframe by the Natural Resources Commission. Later the data was imported into Arc/Info best fitted and clipped to a county boundary extracted from the 1990 TIGER data. Due to originally printing on a line printer the transparent grid was based on 8 acre cells. For vector data: The landuse base map was obtained from Natural Resources Conservation Service. NRCS outlined the landuse polygons transferring it to mylar. Then attributed the polygons with proper landuse, p-factor, and c-factor codes. These base landuse maps were scanned using a Howtek scanner. The data was then registered vectorized, edited, attributed. and edgematched using MIPS software. The final editing and clipping to a county boundary (extracted from the 1990 TIGER data) was done using Arc/Info 6.0 software.
ground condition
None, acknowledgement of the Nebraska Department of Natural Resources and Natural Resources Conservation Service would be appreciated in products derived from this data.
301 Centennial Mall South, P.O. Box 94676
For raster data: When the 8 acre transparent grid was overlaid on the county rectified aerial photograph map and data transferred there was no allowance made for edge matching, rubber-sheeting or projection distortion found in the county aerial photograph map. The data was then keypunched. The keypunched p-factor codes were checked against a list of valid codes through a FORTRAN program on the IBM mainframe. Later data was transported to Arc/Info. Each county was best fitted to a county boundary extracted from the 1990 TIGER files and then clipped to match this boundary. For vector data: When the base landuse maps derived from the unrectified aerial photograph maps were used there was no allowance made for edge matching, rubber-sheeting or projection distortion found in the unrectified county photograph maps. After attributing several error checking programs were run using Arc/Info 6.0 ensuring there were no polygons left unattributed or polygons with wrong attributes.
For raster data: The p-factor codes were checked against a list of valid codes through a FORTRAN program on the IBM mainframe. All codes were valid. A map was generated and a 100% visual check was approved. For vector data: The p-factor codes were checked several times through several error checking programs in Arc/Info 6.0.
For raster data: There were three methods for choosing the p-factor code and entering it in the 8 acre cell grid a. center point - the p-factor type in the center of the cell was used. b. predominant - the p-factor type that contained the largest area of the cell was used. c. island - the p-factor type was completely encircled within the cell, even though it might not be the dominant or center p-factor type of the cell, in order to capture the p-factor type they would enter this one. An example would be a small lake or pond labeled water. From our knowledge the most widely used method was combination of b and c. Method c being implemented whenever it occurred. For vector data: Since the landuse data was drawn at a scale of about 4 inch equal one mile anything below 2 acres would have been incorporated into a larger polygon.
For raster data: medium to low - this data does not meet any standards For vector data: medium - this data does not meet any standards
For raster data: medium to low - this data does not meet any standards For vector data: medium - this data does not meet any standards
spatial and attribute information
For raster data: An 8 acre cell base transparent grid was overlaid onto the county unrectified aerial photograph survey. The 8 acre cell base was used to accommodate printing maps on an 8 line per inch printer. A 2 character cell code was then transferred to sheets by townships. Each township was divided into two strips. A full size strip contains 30 cells. Strips may vary in width to accommodate narrow and odd townships. A third strip is added for a wide township. The length of strip matches the bottom boundary of township. For an exact 6-mile township, the length of strip is 48 cells deep. The county or township boundary is represented by '99' characters. Both first and second strips would, therefore, have 31 cells each for a 6-mile-wide township. The blank or filler spaces are represented by '00' characters. At the end of each 30 cell line was a reference to where the line laid in the county, a nrd number, county number, township, N for North, Range, E or W for East or West range, section, subsection, strip number and line number within the strip. After the county was transferred to sheets and visually edited, it was key punched and transferred to the IBM mainframe where the following programs were run. a. A program was run to check each 2 character p-factor code against a list of valid codes. b. Program run to check invalid line numbers which produced a table of the county showing the number of rows and cells in each strip in a township-range format. This was checked to make sure the correct number of cells and rows were in each strip of a township. c. A program was run to create a file in county map format from the county strip/township format. This county map format file was then imported into ARC/INFO 5.0 using erdassvf and gridpoly commands, in single precision. The p-factor coverage was then best fitted and clipped to a county bound coverage created from the 1990 TIGER data. This data is in Universal Transverse Mercator, zone 14, units meter, North American Datum 1927, Projection Clark 1866. This data was complete on the IBM mainframe in (table 1 - col Publ. P-factor Date). The county p-factor aerial photography map (the base map the data was transferred from) was taken on (table 1 - P-factor Source Map Date) representing ground conditions of the land at that same period. For vector data: The landuse base maps were scanned using a Howtek scanner. They were then registered, vectorized, attributed, edgematched using MIPS 2.90 software. Later in Arc/Info 6.0 the base maps were run through several error checking programs that included checking for unlabeled polygons and polygons with wrong labels. Then clipped to match the 1990 TIGER file county boundary.
301 Centennial Mall South, P.O. Box 94676
Metadata imported.
Internal feature number.
ESRI
Feature geometry.
ESRI
Area of feature in internal units squared.
ESRI
Perimeter of feature in internal units.
ESRI
The PF-CODE is a 2-digit code that provides the actual P-Factor (2nd digit was derived by multiplying the P-Factor *10) and some supporting information. The first digit identifies the presence of structural practices.
Nebraska Department of Natural Resources
See on-line link at Identification_Information <http://dnr.ne.gov/databank/metadata/pfct_legend.html>
Nebraska Department of Natural Resources
The actual value of the P-Factor, the PF-CODE calculated out.
Nebraska Department of Natural Resources
301 Centennial Mall South, P.O. Box 94676
none
After the data was put in ARC/INFO Export format, however, upon request we will output it to another format if you are not able to use this one.
Spatial and attribute information
You can either order by leaving a message over the web site or call Nebraska Department of Natural Resources.
301 Centennial Mall South, P.O. Box 94676