6A-4-4 
Figure 2. Full resolution image detail of a control point. 
A set of 20 images with effective coverage of the region, 
which contained survey control points, was identified. 
These images were organized into a block consisting of 
four flight lines, each containing five images. Two of the 
flights were oriented north to south and were nearly 
coincident. Similarly, the two south to north flight lines 
were also nearly coincident. A total of 17 control points 
were identified and measured within the block. The block 
formation required the measurement of 51 additional tie- 
points. The bundle adjustment resulted in positioning 
accuracies averaging 1.23, 1.24, and 0.43 meters in X, Y, 
and Z, respectively. The orientation accuracies average 
0.079, 0.075, and 0.022 degrees in omega, phi, and kappa, 
respectively. The relatively modest horizontal positioning 
accuracy is due to the limitations in accurately identifying 
the control points. 
The EarthData LIDAR system has a scan FOV of 75 
degrees. At 65 m/s airspeed, the along track spacing is 
about 8 m, while the cross track spacing is roughly 6 m at 
the maximum scan rate of 7.5 Hz and a 2500 m AGL 
flying altitude. The illuminated footprint is 0.6 m. Typical 
accuracies on the ground are 0.25-0.35 m in cross track, 
0.2-0.25 m in along track and 0.15-0.25 m in height error. 
The distribution of the LIDAR spots is shown in Figure 3. 
Using the hierarchical warped image-based surface 
reconstruction technique, DEMs were generated at a 5 m 
grid - this was the closest to the average spacing of the 
irregular LIDAR data. There was no editing of the 
automatically extracted surfaces, although the densely 
built residential areas caused substantial difficulty in the 
processing. For performance examinations, DEMs were 
extracted from different stereo pairs over the test area, and 
the results showed only slight deviations. The 
photogrammetrically derived DEM from the 4K by 4K 
imagery is shown in Figure 4, followed by the LIDAR- 
produced surface in Figure 5. Figures 6 and 7 depict the 
ground truth, topographic surface and extracted objects, 
measured by skilled operators on analytical instruments. 
Figure 3. The distribution of the LIDAR observations 
over the Hagerstown, MD test area, NE quadrant. 
Figure 4. Photogrammetrically-derived DEM from the 4K 
by 4K imagery. 
Figure 5. LIDAR DEM observations over the 
Hagerstown, MD test area.