This document is intended to explain the workflow of extracting height (z) values from elevation models that
correspond to visually identifiable x,y positions of points in a raster image using ERDAS IMAGINE. The workflow
makes use of data provided in the <IMAGINE_HOME>/examples directory.
1. In the GLT Viewer open two viewers and load xs_truecolor_sub.img in Viewer #1 and demmerge_sub.img in
2. From the General section in GLT select Link/Unlink all Views icon.
3. In Viewer #1 zoom into an area of interest from which you wish to extract height values.
4. From the GLT Viewer menu bar select AOI > Tools…
5. From the AOI Tool palette select Create Point AOI icon and place the cursor in the user identifiable position in Viewer #1 (the cursor should change to a cross hair)
6. Left-mouse click and place a point in the image – note a point will appear in both linked images.
7. Repeat steps 5 through 6 until the desired number of points are collected.
8. Save the Point AOI layer by selecting File > Save > AOI Layer As…
Now you will need to convert the pixels to an ASCII file…
9. From ERDAS IMAGINE menu bar select Utilities > Convert Pixels to ASCII…
10. In Input File: (*.img) add the elevation model demmerge_sub.img – since this is the source of the expected height information
11. Select Add for Files to Export
12. Select AOI under Type of Criteria and add the saved Point AOI file (see step 8 above)
13. Define the Output File: (*.asc)
14. Select OK and run the process
15. To view the result select Tools > Edit Text Files…from the ERDAS IMAGINE menu bar – this opens a simple text editor
16. Open the ASCII file generated from Pixel to Table process (see steps 9 – 14 above) in the text editor