The WAC Digital Terrain Model (DTM; or Global Lunar DTM 100 meter topographic model "GLD100") was derived from WAC observations, and covers 98.2% of the lunar surface. Using digital photogrammetric techniques, the GLD100 was computed from 69,000 WAC stereo models. Due to persistent shadows near the poles it is not possible to create a complete WAC stereo map at the very highest latitudes. The GLD100 thus covers from 79° S latitude to 79° N latitude. Since the stereo correlation box is bigger than 100 meters, surface details at the 100-meter scale are not fully resolved. However, each 100-meter square has an average of 26 stereo points within it (for a planet-wide total of 100 billion points), which helps to sharpen the elevation estimate. The resolution, in a formal sense, is probably close to 300 meters, and the accuracy of the elevations is estimated to be about 10 to 20 meters.
The GLD100 is available in the original 100 meters/pixel scale format in ten tiles. The GLD100 is also available in tile format for scales of 256 pixels per degree (ppd) and 128 ppd. At lower resolutions (64 ppd, 32 ppd, 16 ppd, 8 ppd, and 4 ppd), there is a Simple Cylindrical product covering the entire lunar surface from 0° to 360° longitude at each resolution. The LRO Lunar Orbiter Laser Altimeter (LOLA) excels at characterizing the topography of the poles. Since the LRO orbits converge at the poles, LOLA provides a higher resolution topographic model at the poles. For all products except the 100 meter/pixel tiles, the LOLA polar data fills in the WAC "hole at the pole".
The extents of the tiles vary by pixel scale. For the 100 meters/pixel and 256 ppd scales, there are eight quadrangles covering -60° to 60° latitude (equatorial region) and increments of 90° of longitude, projected in the Equirectangular projection. For the GLD100 at 128 ppd, there are eight quadrangles covering -90° to 90° latitude in Equirectangular projection. For all three pixel scales, there are Polar Stereographic maps covering 60° - 90° degrees latitude. Each file is named with the following pattern (see Table 1 for examples):
See the table below for examples:
|Product Name||Latitude Range||Longitude Range||Resolution|
|WAC_GLD100_E300N0450_100M||0° - 60°||0° - 90°E||100 mpp|
|WAC_GLD100_E300N0450_256P||0° - 60°||0° - 90°E||256 ppd|
|WAC_GLD100_E450N2250_128P||0° - 90°||180° - 270°E||128 ppd|
|WAC_GLD100_P900N0000_128P||60° - 90°||0° - 360°E||128 ppd|
|WAC_GLD100_E000N1800_064P||-90° - 90°||0° - 360°E||64 ppd|
|WAC_GLD100_E000N1800_032P||-90° - 90°||0° - 360°E||32 ppd|
|WAC_GLD100_E000N1800_016P||-90° - 90°||0° - 360°E||16 ppd|
|WAC_GLD100_E000N1800_008P||-90° - 90°||0° - 360°E||8 ppd|
|WAC_GLD100_E000N1800_004P||-90° - 90°||0° - 360°E||4 ppd|
The WAC topography was produced by LROC team members at the German Aerospace Center (DLR).
When citing this product, use the following reference:
Scholten, F., Oberst, J., Matz, K. D., Roatsch, T., Wählisch, M., Speyerer, E. J., & Robinson, M. S. (2012). GLD100: The near-global lunar 100 m raster DTM from LROC WAC stereo image data. Journal of Geophysical Research: Planets, 117(E12). doi:10.1029/2011JE003926
If using data poleward of 79 degrees, also use this reference:
Smith, D. E., Zuber, M. T., Neumann, G. A., Lemoine, F. G., Mazarico, E., Torrence, M. H., McGarrey, J. F., Rowlands, D. D., Head, J. W., Duxbury, T. H., Aharonson, O., Lucey, P. G., Robinson, M. S., Barnouin, O. S., Cavanaugh, J. F., Sun, X., Liiva, P., Mao, D., Smith, J.C., & Bartels, A. E. (2010). Initial observations from the lunar orbiter laser altimeter (LOLA). Geophysical Research Letters, 37(18). doi:10.1029/2010GL043751
For more information on LROC Reduced Data Records (RDRs), please refer to the LROC Software Interface Specification (SIS).