The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008 
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Figure 1 
3.2 Prepare blocks 
A block is a group of photos that have been organized into a 
logical subset of project photos. A block can be selected for 
input to the Photo Triangulation, Multiphoto Point 
Measurement, and ISAT point matching and bundle adjustment. 
We use the Block Preparation command(ISAT menu) to define a 
block by entering an ID and then by either selecting the photos 
from a list of project photos or by selecting them from a display 
of photo footprints. Blocks composed of parallel flight-line 
strips with side overlaps should have a one-strip overlap, that is, 
they should both include a common strip. When a strip is itself 
subdivided into different blocks, the blocks should have a 
two-photo overlap. Spanish project includes 500 photo images 
and is divided into upper and lower blocks. Block ID is A and B 
with a one-strip overlap. 
3.3 Perform matching 
Click the ISAT Control Panel (Control Panel command, ISAT 
menu) to display the ISAT Control Panel, Select block A and B, 
select Auto Stretch Images, Reduce Shadow Points, Do Not Use 
GPS/INS on the right side and set up other parameters, then 
click submit, block A and B will be processed separately. We 
can submit the process to be run immediately or schedule it for 
a later time. (The Z/I Job-scheduling Service must be running 
on your computer at the scheduled time). ISAT will generate tie 
points between the photos, using its point-matching technique, 
and perform a bundle adjustment of the points. From the 
Control Panel, we can open the Job Controller or View Log File 
to view information about any running, scheduled ISAT 
processes or read informational messages generated by the 
process. ISAT can create a block project for a processed block 
in a subfolder of the current master project. The name of the 
project is the ID number of the Block. ISAT regenerates pass 
point IDs for each block based on its position in the list, that is, 
1000001 for the first pass point in Block A, 2000001 for the 
first pass point in Block B. 
3.4 Edit weak areas Block A and B, review results and 
adjust 
After auto-matching, we can use Set Active Project(ISAT 
menujor Open command(File menu) to make the Block project 
as current block project, a dialog box will come out to show the 
results of one or more weak areas. Use the Edit Weak Areas 
command, select a weak area from a list. The area on multiple 
overlapping photos, then click OK and the withheld placeholder 
point as positioned on each photo will be presented in a 
multi-photo point measurement environment. If there are an 
adequate number of measured points in the vicinity for a good 
solution, we can delete the point. Otherwise, we should 
manually find and measure a nearby common reference feature 
in each of the photos to connect the multi photos. Continue to 
process with the same method till all weak areas are removed 
from the list. Point matching automatically measures a surface 
feature on multiple displayed photos when we measure it on one 
of the photos. The point matching is enabled by right-clicking in 
a view and then placing a check mark before Enabled on the 
Matching submenu. Clear the check mark whenever you want to 
disable point matching. 
After edition of the weak areas, we will do compute. We can 
view the tie/pass points result in the window of Photo 
Triangulation Results. All the points will have the taxis with the 
V(xy) value. Delete the gross error points, Blunder points and 
one-ray points. Then use Multiphoto Orientation command, 
select six photos from two flight-line strips, to check if there are 
enough tie/pass points between photos. If necessary, input point 
label in Point ID column. In the area lack of tie/pass points, we 
can manually measure tie/pass points. After check, we will do 
relative orientation again. View the tie/pass points result of in 
the Photo Triangulation Results. If there are still big residual 
error points, we can run Multiphoto Orientation command again 
to adjust and re-compute. Repeat such procedure till the 
accuracy is meet. The accuracy of relative orientation for this 
project is RMS^i 12um. 
3.5 Measure control points 
This project has bundle adjustment data provided by GPS/INS, 
so ground control points are less and mainly locate around 
target points. Use Multiphoto Orientation command 
(Orientations mean), or Point Measurement command(ISAT 
menu), go into a multi-photo point measurement environment. 
Input the ground control point label in the Point ID column, use 
Photo\deselect and Find Photos commands to look for the 
photos which will be measured and measure the ground control 
points. 
3.6 Merge the Block measurement results into the master 
project 
Select the Set Active Project or Open command(File menu), 
select the master project(The Merge Block Measurements 
command is available only when the master project is active). 
Use Merge Block Measurements command(ISAT menu), open 
Merge Block Measurements dialog box, select two blocks 
separately which have been processed from Available Blocks 
list, then use Merge Select Block command to merge the 
generated tie/pass points with the master project. 
3.7 Overall bundle adjustment; result evaluation and 
adjust control points 
Select Triangulation command(Orientations menu, Photo 
Triangulation submenu), in Select Photos dialog box, we will 
select all the photos in the master project, click OK and open 
Photo Triangulation Results dialog box, click Options, select 
Absolute in Adjustment Mode, select Enable Precision 
Computation in Adjustment Parameters. Since this project has 
GPS\INS aid for bundle adjustment, in the Given EO/GPS/INS 
Settings parameters area of the Photo Triangulation Options 
dialog box, select the Enable Given EO/GPS check box(If you 
clear this check box, control point and tie point data alone will 
be used to compute the final exterior orientation parameters). 
And because this project has time parameters, we will select