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How to Read the Latitude and Longitude Byte Values from the DTM lunar LRO data


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I think you are referring to the LOLA GDR data set, LRO-L-LOLA-4-GDR-V1.0, http://pds-geosciences.wustl.edu/missions/lro/lola.htm, right? I am not sure whether you are asking how to get the elevation values or the latitude and longitude location. Either way, look in the label file that accompanies a given image, for example http://pds-geosciences.wustl.edu/lro/lro-l-lola-3-rdr-v1/lrolol_1xxx/data/lola_gdr/cylindrical/img/ldem_16.lbl.


To find the elevation in meters for a given pixel, multiply the pixel value by the SCALING_FACTOR and add the OFFSET. In the example label, SCALING_FACTOR is 0.5 and OFFSET is 1737400.


To get the latitude and longitude corresponding to a given pixel, you'll need the values for CENTER_LONGITUDE, CENTER_LATITUDE, SAMPLE_PROJECTION_OFFSET, LINE_PROJECTION_OFFSET, and RES (MAP_RESOLUTION), all of which are found in the label file.  Then plug these values into the map projection equations in the file DSMAP.CAT (http://pds-geosciences.wustl.edu/lro/lro-l-lola-3-rdr-v1/lrolol_1xxx/catalog/dsmap.cat) for simple cylindrical projections or DSMAP_POLAR.CAT (in the same folder) for polar stereographic projections.

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