Cass County Aerial Photography 2011

Tiling is based on sections, and naming is based on township, range and section. 

Cass County, North Dakota

The Leica GeoSystems XPro software was used for downloading and preparing imagery collected with the ADS40 Airborne Digital Sensor for softcopy photogrammetric use. The raw image was download in the field with XPro to a portable workstation. This enabled a quick look at image quality and coverage. Using the Applanix POSgps software package the GPS data was differentially processed against a base station. After the differential GPS solution was checked and verified the Applanix POSproc program was used to compute an integrated GPS/IMU navigation solution at one-second intervals. Using the GPS/IMU trajectory computed by the Applanix POSproc software and the camera calibration, GPro computed a full x,y,z, omega,phi,kappa exterior orientation of each scan line. Using the orientation data file produced the L0 imagery was resampled. The resampling removes most aircraft motion and provides epipolar geometry imagery for stereo viewing, automated aerotriangulation and automated DEM extraction. The Level 1 epipolar-resampled and georeferenced imagery usually will provide a pixel’s true ground location to within a few pixels without any additional processing. To improve accuracy, a fully automatic aerotriangulation process was performed to minimize the residual errors in the GPS/IMU derived exterior orientations. The aerotriangulation also allowed the introduction of ground control and checkpoints to ensure the accuracy specifications were achieved. Automated aerotriangulation of ADS40 imagery was performed with the Socet Set Automatic Point Measurement (APM) tool. A digital elevation model (DEM) was required for orthophoto production. Red River Basin LiDAR Data was used as the DEM for orthophoto creation. Orthophotos were created utilizing Leica Geosystem XPRO software. Orthos were created in XPRO in UTM Zone 14 meters. The orthos were mosaiced together using LizardTech Orthovista. The orthos were then placed in a Fugro Horizons proprietary database format. The database was edited for seamlines, and other artifacts. Since the imagery was calibrated by the system calibration no color correcting was done to the imagery. The imagery was clipped out of the database into the sheet layout generated based on client use requirements. In the clipping stage, the coordinate system and georeferencing was embedded into the header of the TIFF file. The imagery tiles were QC'ed and delivered on an External Hard Drive.