KPLO ShadowCam Derived Data - DTM (Digital Terrain Model)

DTM – Digital Terrain Model

Instrument: KPLO ShadowCam

PDS4 Bundle: urn:nasa:pds:kplo-shadowcamDOI: 10.17189/y89z-kt98

High-resolution DTMs (Digital Terrain Models) are generated from stereo image pairs captured by ShadowCam. These models include confidence maps and color-shaded relief maps, providing detailed topographic information essential for understanding the lunar surface's morphology. For each ShadowCam DTM, several related products are produced. The are grouped as one product in ODE product search result details page. Please see details below.

  • Ortho-rectified images: ortho-rectified images are provided for each source image. In most cases where multiple stereo sets were used, a mosaic of the nadir ortho-rectified images is available at two resolutions (DTM resolution and image resolution). Because nadir images are typically somewhat higher in resolution than slewed images, a third, higher resolution for the nadir images and/or the mosaic may also be provided in some cases.

  • Slope map: The slope map is generated from the DTM using the GDAL command gdaldem slope with Horn's algorithm. It is made at the same pixel scale as the DTM with units of slope in degrees.

  • Colorshades and colorshade legends: The colorshade images are color-coded topography draped over the shaded relief. The colorshade legend explains what the color means. There are two versions: a discrete colorshade that bins the data to emphasize topography, and a gradient colorshade that is a continuous color map.

  • Color slope map and slope map legend: The color slope map is the color-coded slope (in discrete increments) draped over the shaded relief. The slope map legend explains what the color means.

  • Shaded relief: The shaded relief image is generated with the Sun azimuth of 315 degrees (northwest) and Sun altitude of 45 degrees.

  • LOLA offset plots: There are four plots showing offsets between the final DTM and co-located LOLA data. The first plot is a difference map created by subtracting the DTM elevations from the LOLA point elevations at each location. The other three plots are created by aligning the LOLA tracks to the final DTM, with the alignment results displayed in the x, y, and z dimensions.

  • DTM mosaic subproducts: In some cases, where DTMs are made up of numerous stereo pairs, numerous individual DTMs (each created from two images) are created and then mosaiced together into the final DTM mosaic. For each individual DTM, orthophotos are also created from the source images and confidence maps. Where possible, these individual DTMs, orthophotos, and confidence maps are provided as well as the final DTM and orthomosaic.

  • Readme: The readme file contains descriptions of the DTM, precision and accuracy information, description of known artifacts, naming convention, related products, and confidence table lookup.

ShadowCam DTMs was controlled to LOLA elevations data. Known artifacts are present in some, but not all, ShadowCam DTMs. Please look at the terrain shaded relief and the confidence map to detect these before using the DTM! Some general notes for ShadowCam DTMs artifacts are listed below.

  • Boxes: Some DTMs have rectangular areas that are usually about 0.5-1.0 m different in elevation from the surrounding areas. These are artifacts of the processing algorithms used in SOCET SET ((c) BAE Systems). There may be groups of these boxes. They are almost impossible to edit out, so the user should look for such artifacts in a terrain shaded relief map before using the DTM for analysis.

  • Mosaic seams: ShadowCam stereo is made up of pairs of images acquired on different orbits where the total parallax angle is greater than 12 degrees. Larger area coverage can be built up by acquiring many images with alternating geometries. Thus, multiple pairs of images overlap creating multiple stereo models. These stereo models are stitched together into one DTM mosaic. In some mosaics, the seams between the stereo models may be visible as long lines, usually up to 1 m difference. These seams can be difficult to remove from the whole DTM.

  • Faceted areas: Areas that were very bland (low contrast) or deeply shadowed with low contrast and low signal may have a "faceted" look to them. This artifact is caused when the processing algorithm is not able to correlate the images and must interpolate to fill in the pixel. The terrain data in these areas are not trustworthy. Use the confidence map to look for "suspicious" data points.

  • Noise: DTMs have varying levels of noise from low signal images, low incidence angle, and jitter. The amount of noise may be detected using the slope map or the confidence map.

  • Shadowed regions: Where the input images have dark shadows, there is insufficient data for stereo matching, generally resulting in noise or faceted areas. These shadowed areas are generally removed from the final DTM (resulting in areas of null data), although small shadows may remain and appear as interpolated data or noisier regions.

ShadowCam DTM data and related products have the following file names:

shadowcam_dtm_xxxx-xxxxxxx_ayyybzzzz<_s**>_dtm_#m.ext (DTM products)

shadowcam_dtm_xxxx-xxxxxxx_ayyybzzzz<_s**>_<description>_#m.ext (Related DTM products)

where:

shadowcam_dtm = a ShadowCam DTM product

xxxx-xxxxxx = words specifying the sitename

a = projection type

e = equirectangular

p = polar stereographic

yyy = center latitude to the nearest 10th of a degree

b = n for northern hemisphere, s for southern hemisphere

zzzz = center longitude to the nearest tenth of a degree. The longitude domain for ShadowCam DTMs is 360 positive east.

s** =

dtm_#m = DTM at a pixel scale of # meters

description = type of product

for Ortho-rectified images, it is

- ortho_<name of the NAC image>_resolution

- orthomosaic_resolution

for slope map, it is slope

for Colorshades and colorshade legends,

- colorshade-disc for the discrete colorshade image

- colorshade-disc_legend for the discrete colorshade legend

- colorshade-grad for the gradient colorshade image

- colorshade-grad_legend for the gradient colorshade legend

for Color slope map and slope map legend,

- color-slope for the color-slope map

- color-slope_legend for the slope map legend

for Shaded relief map, it is shade

for LOLA offset plots,

- lola-offsets-diff_plot for the difference map

- lola-offsets-<x/y/z>_plot for the offset plots

for DTM mosaic subproducts, it is slope

for Readme file, it is readme

 

ext = file extension for associated products

cub = ISIS cube files

png = browse image files

tif = tif image files

_cog.tif = COG - pyramidal product files

txt = text files

xml= PDS4 XML labels

In ODE, ShadowCam DTM data products have the following product IDs:

shadowcam_dtm_xxxx-xxxxxxx_ayyybzzzz_dtm_#m

shadowcam_dtm_xxxx-xxxxxxx_ayyybzzzz_s**_dtm_#m

 

More information about the ShadowCam DTM data products can be found in the following documents:

  • Manheim, M.R., Henriksen, R.V., Wagner, C.H., Michaud, and the ShadowCam Team,., ShadowCam Digital Terrain Models Of Permanently Shadowed Regions, 2024 LPSC LV, Abs. #1294.

  • Henriksen M.R., Manheim M.R., Grieser S.A., Carr N.F., Brown H.M., Collins1 W.M., Wagner RV., and Robinson M.S., ShadowCam Derived Mosaics, Digital Terrain Models, And Other Products, 2025 LPSC LVI, Abs. #2571.