LRO NAC IFP ASP DEM - README
Overview
This dataset, titled NAC_IFPASP_14820N071500_1, is part of an automated processing pipeline designed to generate Digital Elevation Models (DEMs) from Lunar Reconnaissance Orbiter Narrow Angle Camera (LRO NAC) stereo imagery. The pipeline utilizes ISIS software and the Ames Stereo Pipeline (ASP; Beyer et al. 2018), along with custom Bash, Python, and MATLAB scripts, to calibrate, process, and archive high-resolution DEM products and related datasets.
Product Filename Descriptions
The pipeline produces a variety of products, including:
- Digital Elevation Model (DEM): GeoTIFF files representing elevation data in meters relative to datum.
- Slope Map: GeoTIFF file representing elevation slopes in degrees.
- Good Pixel Map: GeoTIFF files indicating valid pixels in processed images.
- Hillshade Map: GeoTIFF files generated to enhance the visual relief of terrain.
- Colored Hillshade Map: Enhanced hillshade maps with color overlays for improved interpretability.
- Orthomosaics: Ortho-images using the accompanied DEM for map projection in image resolution. There is one ortho-image for the left and one for the right stereo image.
- Readme: The readme file contains description of the DEM, precision and accuracy information, description of known artifacts, naming convention, and related products.
Image Name Conventions
All output files follow a standardized naming convention to facilitate data management and retrieval. The format is as follows:
NAC_IFPASP_{Latitude}{Hemisphere}{Longitude}_{Counter}_{datatype}.TIF
Where:- NAC: Represents the Narrow Angle Camera instrument on the Lunar Reconnaissance Orbiter spacecraft.
- IFP: Indicates the processing place, which is the Institut für Planetologie, Universität Münster, Germany.
- ASP: Denotes that the product was generated using the Ames Stereo Pipeline.
- {Latitude}{Hemisphere}{Longitude}{Counter}: Indicates the latitude of the scene center (e.g., 33877S for -33.877° South) and longitude (e.g., 001187 for 1.187° East), both rounded to 1e-3 degrees. If datasets happen to have the same set of coordinates, the counter discriminates individual datasets.
- {datatype}: Describes the product type (e.g., DEM, SLOPE, GOODPIXEL, SHADE, CLRSHADE, <NAC Image ID>_ORTHO).
- .TIF: All products are saved as GeoTIFF files.
Files in this dataset:
| Digital Elevation Model | NAC_IFPASP_14820N071500_1_DEM.TIF |
| Dataformat | int16 |
| NoData value | -32767 |
| Color Type | grayscale |
| Number of Bands | 1 |
| Hill-Shade | NAC_IFPASP_14820N071500_1_SHADE.TIF |
| Dataformat | uint8 |
| NoData value | none set |
| Color Type | grayscale |
| Number of Bands | 2 |
| Colored Hill-Shade | NAC_IFPASP_14820N071500_1_CLRSHADE.TIF |
| Dataformat | uint8 |
| NoData value | none set |
| Color Type | truecolor |
| Number of Bands | 4 |
| Orthoimages | NAC_IFPASP_14820N071500_1_M1113695073_ORTHO.TIF, NAC_IFPASP_14820N071500_1_M1113709279_ORTHO.TIF |
| Dataformat | single |
| NoData value | -3.402822655088904e+38 |
| Color Type | grayscale |
| Number of Bands | 1 |
| Goodpixel Map | NAC_IFPASP_14820N071500_1_GOODPIXEL.TIF |
| Dataformat | uint8 |
| NoData value | none set |
| Color Type | truecolor |
| Number of Bands | 3 |
| Slope Map | NAC_IFPASP_14820N071500_1_SLOPE.TIF |
| Dataformat | single |
| NoData value | -9999 |
| Color Type | grayscale |
| Number of Bands | 1 |
Product created:
October 12, 2023
Basic Processing Step Description
The processing pipeline comprises the following major stages:
- Data Selection and Ingestion
- Stereo image pairs are selected based on overlapping conditions and temporal proximity (within 10 LRO orbit periods).
- A MATLAB script filters and records these pairs in a text file to prevent duplicate processing.
- Preprocessing
- Raw NAC images are calibrated and map-projected using USGS ISIS (versions 3.5.2 and 5.0.0; Becker et al., 2013). The map projection utilizes the 118 m/pixel resolution LRO LOLA DEM (Barker et al., 2016).
- Preprocessing and mosaicking are applied to LRO NAC left and right channels to generate seamless image pairs using NASA Ames Stereo Pipeline (ASP) script “lronac2mosaic.py”.
- Stereo Processing (Main Processing)
- The Ames Stereo Pipeline (ASP) is used to perform bundle adjustment, stereo matching, and DEM generation.
- Processing scripts dynamically read projection parameters and image metadata, adjust map settings, and integrate reference data (e.g., from LRO LOLA) for correcting DEMs.
- Postprocessing and Archiving
- Final outputs (DEMs, orthoimages, and good pixel maps) are archived.
- Additional derived products such as slope maps, hillshade maps, and colored hillshade maps are generated and archived as well.
LROC NAC Source Images:
M1113695073 L/R, M1113709279 L/R
Projection:
Stereographic: Center Latitude: 14.8199 Center Longitude: 71.4995
Download Links:
Quality Metrics:
- Mean Error against LRO LOLA DEM (Barker et al., 2016): -2.0992 meters
- Standard Deviation to LRO LOLA DEM (Barker et al., 2016): 8.7991 meters
- Pixel Size: 3.691 meters
Version Number: 1.0
Reference:
For more information on the methodology of the DEMs, see:
https://zenodo.org/records/15469684/files/ELS_2025_Schmedemann_ea_v2.pdf
RDR SIS: http://pds.lroc.im-ldi.com/data/LRO-L-LROC-5-RDR-V1.0/LROLRC_2001/DOCUMENT/RDRSIS.PDF
Links to Browse Images:
General Notes:
Known Artifacts:
These are known artifacts present in some, but not all, LROC NAC DEMs.
These artifacts may not be present in this DEM! Look at the terrain shaded relief and the goodpixel map
to detect these before using the DEM!
- NACL and NACR seams
There are two NAC cameras (NACL & NACR) on board LRO. Stereo images are collected by acquiring images on two different orbits so the total parallax angle is greater than 12 degrees. The overlap between the four images (two pairs of NACL and NACR) provides three or four stereo models from which to collect elevation data. These stereo models are stitched together into one DEM. In some DEMs, the seams between the stereo models may be visible as long lines, usually up to 5 m difference. These seams are difficult to remove from the whole DEM.
- 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 is due to the processing algorithm 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 Good Pixel Map to look for "suspicious" data points.
- Noise
DEMs have varying level of noise from low signal images, low incidence angle, and jitter. The amount of noise may be detected using the slope map or the Good Pixel 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 DEM (resulting in areas of null data), although small shadows may remain and appear as interpolated data or noisier regions.
Literature References
- Barker, M. K., Mazarico, E., Neumann, G. A., Zuber, M. T., Haruyama, J., & Smith, D. E. (2016). A new lunar digital elevation model from the Lunar Orbiter Laser Altimeter and SELENE Terrain Camera. Icarus, 273, 346-355. https://doi.org/10.1016/j.icarus.2015.07.039
- Beyer, Ross A., Oleg Alexandrov, and Scott McMichael. (2018). The Ames Stereo Pipeline: NASA’s open source software for deriving and processing terrain data. Earth and Space Science, 5. DOI:10.1029/2018EA000409.
- Becker, K.J. et al. (2013). ISIS Support for NASA Mission Instrument Ground Data Processing Systems, Lunar and Planetary Science Conference, XLIV, abstr. 2829.
NAC DEM centered at 14.820N, 71.500E (1) DTM
Color-shaded Relief (click for more information)
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