Instructions to convert a MAP file to other formats

Convert to FITS

• Use the AltWG toolset to get the proper format

Maplet2FITS --configFile fitsConfig_orex_spc.ini RAD201.MAP RAD201-fullv1.fits

• An example ini file can be found here fitsConfig_spc.ini.

• Notes from Ray Espiritu on 5 May 2020 about the ini file "It may look familiar as it has the same format as the nft config files you send me for generating MLNs. Format is KEYWORD#value. Notice that “//” denotes comment lines. This does not allow you to add custom keywords; the keyword has to exactly match a keyword that is normally populated in the fits header."

• There will still be some header information you will want to change. For this use ChangeFitsHeader, also part of the AltWG distribution toolset.

• More notes from Ray Espiritu on 5 May 2020 for "This tool allows you to add,delete, or modify keywords in the header. Run “ChangeFitsHeader –examples” to see examples for each operation (add, delete, modify, change). There is a limitation inherent in the fits format in that the new fits header cannot have a size difference of more than 2880 bytes from the old fits header. You shouldn’t encounter that if you are adding or deleting a handful of keywords."

Convert to GeoTIFF

Fits file to tif

• First, convert to FITS format (and update headers as necessary).
• Use GDAL to convert from FITS to GeoTIFF

gdal_translate -b 3 -a_srs RAD201-v5.prj -a_ullr -8510 8510 8510 -8510 RAD201-fullv1.fits RAD201-fullv1.tif

• An example of the prj file can be found here, and can be viewed with a text editor such as "vi". RAD201-v5.prj

• The -a_ullr is giving the bounds of the DTM in meters. The math is "Upperleft X = (Q*2+1) * GSD (in meters) / 2 * -1" and "UpperLeft Y = (Q*2+1) * GSD (in meters) / 2". So if the GSD is 20 m with a Q of 425, the math is (425*2+1) * 20 / 2 * -1 = -8510

• The -a_scale option will tell the geoTiff how to convert the DN value to physical units. I am still working out how to determine the value needed.

• If you are converting a fits file with multiple bands, you can specify a particular band with the -b <band #>

• GDAL works with both fits and pgm
• If your file has multiple bands, use the -b option to select a band

Use spheremapsB

Use this when you want to fix the map projection of the DEM. The output will be a PGM. Imbeded in the header of the pgm you will find relevant information, such as "REFERENCE RADIUS", HTMAX (height max), HTMIN (height min), and HTSCL (height scale, which is used to convert DN to distance)

• Often you will want the "REFERENCE RADIUS" to be the datum for the object, and not the value of the maplet VLM (though this is subject to change).
• DN of zero is for "No Data"
• For 16-bit, the DN will be 1 to 65535
• To convert from DN to distance, you will take (DN - 1)*HTSCL + HTMIN. This value will be distance from the "REFERENCE RADIUS".

Set proper values

This is still a work in progress, but I think this is close (26 Aug 2020). When you initially create the tif, the "values" will be in DN space and you will need to convert them to meters. You do this by setting the scale (multiplicative) and offset (additive), and then separately unscaling the pixels. You can't do these processes with one command line, you have to use two.

• Because of the how the data is recorded (see spheremapsB above), the scale will be HTSCL and the offset will be HTMIN - HTSCL.

gdal_translate -a_srs INGV02_jrw.prj -a_scale 2.406482777E-03 -a_offset -3.627833373E+03 -a_ullr -4552.5 4552.5 4552.5 -4552.5 ING2EQ_DTM.pgm ING2EQ_DTMtemp.tif
gdal_translate -unscale -ot Int16 ING2EQ_DTMtemp.tif ING2EQ_DTM.tif

• When using unscale, you also have to be sure you output in the correct format, so use -ot for that.
• Always check the output to make sure you have the proper values. Do this using gdalinfo

gdalinfo -stats ING2EQ_DTM.tif

Below are the gdalinfo stats from Mercury_Messenger_USGS_DEM_Global_665m_v2.tif

Band 1 Block=23040x1 Type=Int16, ColorInterp=Gray
  Min=-10764.000 Max=8994.000 
  Minimum=-10764.000, Maximum=8994.000, Mean=-478.084, StdDev=2265.894
  NoData Value=-32768
  Offset: 0,   Scale:0.5
  Metadata:
    STATISTICS_MAXIMUM=8994
    STATISTICS_MEAN=-478.0844394489
    STATISTICS_MINIMUM=-10764
    STATISTICS_STDDEV=2265.8943218627
    STATISTICS_VALID_PERCENT=100

• The "Min" and "Max" are showing as being accurate to the third decimal. They are not. They will only increment as whole numbers. They really are an int.