PROJECT NAME
 Sander Crater

MDIS NAC SOURCE IMAGES
  1. EN0218289175M
  2. EN1012773887M

TECHNICAL CONTACT INFORMATION
  NAME		ARIZONA STATE UNIVERSITY
  INSTITUTION	ARIZONA STATE UNIVERSITY

DATE CREATED
  October 2, 2016

- Products are tied to MLA elevations with mean error of -60.09 m and standard deviation of 66.09 m.
  This error is a combination of error from the LOLA points and the DTM, and may give a measure of the horizontal
  and vertical accuracy of the DTM.
- The reported precision error from SOCET SET is 44.74 m.
- SOCET SET NGATE v5.6 was used to extract terrain.
- Post spacing in DTM is 107 m.


GENERAL NOTES:

KNOWN ARTIFACTS
  These are known artifacts present in some, but not all, MDIS NAC DTMs.
  These artifacts may not be present in this DTM! Look at the terrain shaded relief and the confidence map
  to detect these before using the DTM!
  - 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
	There are two or more stereo pairs stitched together into one DTM for DTM mosaics. While steps are taken
	to eliminate or reduce seams between stereo models, they may be visible as long lines. These seams have 
	elevation offsets less than the precision of the DTM, but the user should still looks for these artifacts
	before using the DTM for analysis.
  - 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
	confidence map to look for "suspicious" data points.
  - Noise
	DTMs have varying level of noise from low signal images and low incidence angle. The amount
	of noise may be detected using the slope map or the confidence map.

PDS PRODUCT NAMING CONVENTION
  The PRODUCT_ID naming convention for LROC NAC DTMs is: MSGR_DEM_ASU_pp_aaaaaBB_mm_sss_c_Vnn.ext where
	- MSGR_DEM_ASU = indicating it's a Messenger DEM product produced at Arizona State University (ASU)
	- pp = two letter code indicating projection type
		EQ = equirectangular
		NP = north pole stereographic
		SP = south pole stereographic
	- aaaaa = 5 character designation for the sitename (5 characters)
	- BB = 2 character designation for the stereo pair
		2 digits = a uniquely numbered stereo pair for that site
		MS = mosaic of the site containing all the stereo pairs
	- mm = two character product type (explained in detail below)
		DM = digital elevation model (primary 32-bit product)
		CF = confidence map
		CL = colorshaded relief map legend
		CS = colorshaded relief map
		OR = 16-bit orthorectified images
		SL = slope map legend
		SM = slope map
		TS = terrain shaded relief map
		RM = readme (this file)
	- sss = map scale in meters/pixel
	- c = file type code
		I = PDS image format file (.IMG)
		J = JPEG 2000 file
		T = GeoTIFF file format (.tif)
		S = text file with list of source products (.txt)
	- nn = 2 digit version number
	- .ext = file extension
  Example: MSGR_DEM_ASU_EQ_SANDR01_DM_100_I_V01.IMG is a Messenger DEM produced at ASU of Sander Crater consisting
           of a single stereo pair designated '01' at 100 m/px in Equirectangular projection in PDS image format.

RELATED DEM PRODUCTS
  For each DEM produced, we also produce several related products, indicated by the product types used in the 
     naming convention above. Some of these are only available as GeoTIFFs in the PDS EXTRAS directory.
  - 16-bit ortho-rectified images
	We provide 4 ortho-rectified images, each image used for the stereo model at both the resolution of the DEM
	and at the lowest native resolution of the pair. These are provided in PDS image format.
  - Colorshaded relief map and legend
	The colorshade image is the color-coded topography draped over the shaded relief. The colorshade legend
	indicates how the colors correspond to elevation. These are provided only in GeoTIFF format in the EXTRAS
	directory.
  - 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 shows how the colors correspond to slope (in degrees). These are provided only in GeoTIFF
	format in the EXTRAS directory.
  - Shaded Relief
	The shaded relief image is generated with the sun azimuth of 315 degrees (northwest) and sun altitude of
	45 degrees. This product is provided only in GeoTIFF format in the EXTRAS directory.
  - Confidence map
	The confidence map gives users a little guidance on what elevation values to trust and not to trust.
	Refer to the CONFIDENCE MAP TABLE LOOKUP below for the description of the pixel values. This is provided
	in PDS image format.
  - DEM in GeoTIFF format
	We also provide the DEM in GeoTIFF format in the EXTRAS directory to allow users more flexibility in 
	using the DTM. 
  - Readme
	The readme file contains description of the DTM, precision and accuracy information, description of known
	artifacts, naming convention, related products, and confidence table lookup.

CONFIDENCE MAP TABLE LOOKUP
  Value	 Description
    0	 NoDATA, outside boundary (e.g. out of stereo pair overlap)
    1	 Shadowed
    2	 Saturated
    3	 Suspicious (edge, corner, did not correlate, etc.)
    4	 Interpolated / Extrapolated (e.g. from neighbor pixels)
  10-14	 Value range of successful correlations
    15	 Manually edited