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Working with PDS data

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Assigning Map Information to PDS Images in ENVI


Jennifer Ward

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In ENVI, you can assign map information to a PDS image based on values from the PDS label.

 

1. Download an image and corresponding PDS label file (.lbl extension) to the same directory.

2. Open the image in ENVI. It will not be map projected.

3. Select File > Edit ENVI Header and select the image. Click OK.

4. From Edit Attributes, choose Map Info...

5. Click Change Proj.

6. Unless you already have the correct lunar projection, create a new one (steps below assume projection does not exist).

7. Click New... on the Projection Selection dialog box.

8. Enter values based on label. For example, sphere radius 1738000 (notice in meters), projection type sinusoidal, 0 false

easting and northing, 74 central meridian longitude. (False easting/northing not in the label.)

9. Save projection and map_proj file. Select newly created projection.

10. In the Edit Map Information dialog, enter values from the label. For example, image coordinate x,y of 1.5,1.5 (the upper left

corner) might be 0,50 with pixel size of 400 m/pixel. Click OK to save map information and OK to save header.

 

Due to a technical issue, the original comments on this blog post were lost. A transcription of the comments can be found below.

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R/Rc is the ratio of the actual reflectance spectrum to the continuum spectrum (basically a straight line connected over the absorption band).

ENVI has a Continuum Removal tool (see https://www.harrisgeospatial.com/docs/ContinuumRemoval.html) which looks to me like it performs this calculation for you. If you start with the M3 reflectance images (files that end in "_rfl.img") and use the Continuum Removal tool, the result should be the ratio R/Rc for each band. Then you can use the Band Math tool to put together the sums needed to calculate integrated band depth.

Note: I'm not all that familiar with M3 data processing, so you might want to confirm this is the right approach with someone from the M3 team before using this in any publications.

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