Data Set Overview : The data set consists of gridded, resampled shape maps known as GDRs. The data product is an image object contained in a data file, and a detached PDS label file with a pointer to the data file as well as meta-data information. The values are planetary radii relative to a sphere with a defined offset, and counts giving the number of observations in each individual pixel, or zero where values are interpolated. The label file that accompanies each GDR defines the timespan over which the data values were collected, as well as the product creation time. The shape models are provided in PDS compliant IMG format at resolutions of 2^n pixels per degree in cylindrical equidistant projection, and in north polar stereographic projection at resolutions of integral numbers of meters, typically 250-1000, and a map at 64 pixels per degree at the north pole, or 665.24 m. Pixels represent finite areas rather than discrete points, as scan-line raster images. The center of the upper left pixel is defined as line 1 and sample 1. Simple cylindrical images may extend from -180 to 180 degrees longitude or from 0 to 360 degrees longitude, positive East. A polar model is a square raster image whose four central pixels surround the north pole. The [LINE,SAMPLE]_PROJECTION_OFFSET elements are the pixel offset from line and sample (1.0, 1.0) to the map projection origin defined by the CENTER_LATITUDE and CENTER_LONGITUDE elements. The design of the MESSENGER mission [SOLOMONETAL 2007] and the ranging distance of the MLA allow for data collection primarily in the northern hemisphere, while sparse data were collected from the equator to 18 S. Dataset projections are given in DSMAP.CAT and DSMAP_POLAR.CAT. A geospatially labeled, JPEG2000 format product is additionally produced with accompanying XML and LBL files as an alternate format to the PDS IMG format. Pixel level information can be read from these files using an appropriate reader. The data providers do not provide support for commercially available data analysis products. Additionally, internally produced software for the visualization or interpretation of data products is not provided. Attention must be paid to the 0.5 scale factor that must be applied to digital numbers to obtain meters. A JPG file of the data product is also provided for user convenience. The density of observations accumulates over time, and warrants gridding at increasing resolution as coverage improves. As of the end of the nominal mapping mission, more than 50% of pixels at 1 x 1 degree resolution in the northern hemisphere had one or more data values. Orbital phases where ranging could reach below the equator provided some measurements to as far as 16.7 degrees south, and offnadir slews reached as far north as 89.98 degrees north. The density of observations is given in the accompanying altimetry counts images, where values greater than 0 indicate the number of successful ranges. The vertical resolution of the laser is approximately 30 cm. Horizontal resolution varies due to factors such as surface slope and roughness, the distance between the spacecraft and the surface, and the pointing angle of the altimeter. The lowest point observed is 2433.598 km, or -5.802 km relative to a 2439.4 km datum at 28.104N, 56.349E in Rachmaninoff crater. The polar crater inside Prokofiev at 85.5N, 63.87E is nearly as deep (-5.64 km) although at a higher equipotential level. The highest area is 4.743 km, at 116.84 to 116.89 E, 30.31 to 30.34 N, on the rim crest surrounding Raditladi Crater.

Data Confidence Note : As GDR products are constructed using RDR and CDR data records, the Data Confidence Notes in CDR_RDR_DS.CAT should be consulted. GDR topographic products have a data span from -18 to 89.98 degrees N latitude. This data release (entire mission through 04/30/2015) incorporates 27 million high-quality observations from 3279 orbital profiles for which values for topography range from -5.8 km to 4.75 km relative to a sphere of radius 2439.4 km.