An orthoimage is remotely sensed image data in which displacement of features in the image caused by terrain relief and sensor orientation have been mathematically removed. Orthoimagery combines the image characteristics of a photograph with the geometric qualities of a map. For this dataset, the natural color orthoimages were produced at 6-inch pixel resolution. The design accuracy is estimated not to exceed 3.3-feet diagonal RMSE. The projected coordinate system is State Plane with a NAD83 datum. There is no image overlap been adjacent tiles.
These data have been created as a result of the need for having geospatial data immediately available and easily accessible in order to enhance the capability of Federal, State, and local governments and emergency responders.
None. Acknowledgement of Cornerstone Mapping, Inc. would be appreciated for products derived from these data.
City of Lincoln and Nebraska Health and Human Services
During orthophoto production, automatic image dodging (radiometric editing) was performed to minimize frame-to-frame tone differences. The dodging reduces the effects of camera exposure settings, sun angle, and general atmospheric conditions of multiple image dates.
The horizontal positional accuracy and the assurance of accuracy depends, in part, on the accuracy of the data inputs to the orthorectification process. The location of municipality provided photo-identifiable ground control and contractor exterior orientation were evaluated on the GeoTiff image and compared with their surveyed values in order to determine an overall accuracy of the project. After image measurement was completed and compared with surveyed locations, an RMSE for radial error was calculated for the ortho images. This value is an estimate of the horizontal accuracy of the tiles expressed in feet.
Federal Geographic Data Committee, 1998, Geospatial Positioning Accuracy Standard, Part 3, National Standard for Spatial Data Accuracy (NSSDA), FGDC-STD-007.3-1998
Used to provide ground elevations for orthophoto production.
True color digital aerial photography flown at 3,000 feet above average meant terrain (AMT). Provides the imagery for the digital orthophoto.
Horizontal control used to perform quantitative horizontal positional accuracy assessment.
The aerial photos were acquired using a digital imaging system. The entire flight(s) was recorded using a tightly coupled GPS and Inertial Measurement Unit (IMU). Post processing was performed on the IMU data using local CORS basestation data. For each photo the exterior orientation was derived from the IMU solution. Vertical control for the ortho production was obtained using DEM data. Every image was orthorectified, image dodged, and tone balanced performed using Leica Photogrammetry Suite software (version 8.7).
Internal feature number.
3131 Merrill St