I am using Imagine Photogrammetry for orthorectification of satellite images. In some cases when I try automatic measurement of tie points I got error message "Not enough overlap"
Is there some settings that I can change to use APM with smaller overlap between images.
There is no minimum overlap for APM. If your block is a regular aerial photo block, “Default Distribution” should work fine. The default APM distribution will be ideal for flight-direction overlap 60% and side overlap 20% or more.
If your overlap is 10% then use “Defined Pattern”. If you select Defined Pattern, then the options Starting Column, Starting Line, Column Increment, and Line Increment become active. Using those options, you can define the exact placement of tie points throughout the images of the block. With this option, you also define the intended number of points per pattern and enter starting line/column as well as line and column increments.
Select View Graphic to control the tie point pattern using pixel locations or percentages from image edges if desired. You can go as low as 1%. Changes you make will display immediately. APM will usually find multiple points per pattern area but it thins some automatically. Check Keep All Points to preserve them all.
And in case the "Defined Pattern" does not work; one thing you could alter is the Initial Accuracy on the APM property dialog (Strategy Tab). The default is 10%. You may try reducing the percentage, for example chage it to 5% if the overlap is 5%.
But first try combinations of starting column/line/number of points.
