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LOLA LBL Corrections

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fermigas edited this page Oct 13, 2018 · 3 revisions

Examples... Digital topography... Sources of Planetary DEM Data...

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Description

In the early releases of LDEM_4.LBL and LDEM_16.LBL, the "OFFSET" of the raw data values was incorrectly listed as "1728216." (meters). This was corrected to "1737400." on 22 Mar 2010. However the new *.LBL files contain new errors making the LOLA *.IMG files unreadable by releases of LTVT prior to 23 Mar 2010, and causing the polar stereographic DEM's to display with an incorrect scale. New *.LBL files were uploaded twice on 25 Mar 2010, the second appearing close to correct, however containing a change in MAP_SCALE units not anticipated by LTVT.

Details

*Correcting scale of LOLA polar stereographic .LBL files dated 22 Mar 2010:

  1. Open the *.LBL file with a text editor, such as Notepad or WordPad
  2. Find the line towards the end of the file the line "MAP_SCALE = 100 "
  3. Change the number from "100" to the correct scale (as indicated in the earlier descriptive text), which can vary from 20 to 400 (meters).
  4. Also look for the line that says "CENTER_LATITUDE". The number should be either "90 " for north polar projections, or "-90 " for south polar projections. If the "-" sign for south polar projections has been omitted, it needs to be inserted.
  5. Save the file and exit the text editor.

*Making LOLA .LBL files dated 22 Mar 2010: readable by earlier versions of LTVT
(this manual editing is not necessary for LTVT_v0_21_3x.exe released 23 Mar 2010 or later)

  1. Open the *.LBL file with a text editor, such as Notepad or WordPad
  2. Find the line under "OBJECT = UNCOMPRESSED_FILE" saying something like FILE_NAME = "LDEM_64.IMG".
  3. Change the word FILE_NAME to ^IMAGE.
  4. In the polar DEM's, find the line "LINE_SAMPLES" (under "OBJECT = IMAGE). Correct the "LINE_SAMPLES" number so that it equals the one listed on the "LINES" line preceding the "LINE_SAMPLES" line (do not make this correction to the simple cylindrical global DEM's). Also correct the "MAP_SCALE" of the polar DEM's as described above.
  5. Save the file and exit the text editor.

*Making polar LOLA .LBL files dated 25 Mar 2010: readable by earlier versions of LTVT
(this manual editing is not necessary for LTVT_v0_21_3x.exe released 25 Mar 2010 or later)

  1. Open the *.LBL file with a text editor, such as Notepad or WordPad
  2. Find the line towards the end of the file the line "MAP_SCALE = nnn <m/pixel>" where "nnn" is a number.
  3. Change <m/pixel> to .
  4. Save the file and exit the text editor.

This page has been edited 3 times. The last modification was made by - JimMosher JimMosher on Sep 20, 2010 2:17 pm

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