How do I add grid and coastlines on a True-color image?

To add grid and coastlines on a SeaDAS created True-color image,
users may follow several steps:

(1) Use new SeaDAS utility "l1mapgen" (available in SeaDAS 5.2) to create a true-color picture
at Unix/Linux command prompt.

  l1mapgen ifile=xx.L1B geofile=xx.GEO  ofile=xx.ppm resolution=250 threshold=0.01 width=3000 north=50 south=40 west=-95 east=-80 atmocor=1

Or use old SeaDAS utility 'msl1tcpcbox' (SeaDAS 5.1 or older):

  msl1tcpcbox -a -- 600 10 -30 -60 -20 0 S2003324152722.L1A_MLAC S2003324152722.L1A_MLAC.ppm

(2) Convert the ppm file to a PNG file for SeaDAS display:

      pnmtopng A2008123045.ppm > A2008123045.png

(3) Because the true-color picture is mapped with Plate Carrée projection which matches
SeaDAS's equatorial cylindrical equidistant projection, user can remap the original L1B image
over the same region (same lat/lon range) with the same XY size .

(4) Generate Grid/Coastlines from this mapped image and save them as a 'flat file' graphic.

Graphics -> Save ->flat file

Text annotation can be added and saved at this step.

(5) Go back to the true-color picture and overlay those saved graphics on the picture.
Graphics -> Load -> flat file

This process is mainly for visual viewing. The accurracy of the coastline match needs
further validation. Possible mismatch could come from image remapping.