Data Set Overview
    =================
      The data set consists of digital elevation models (DEM) of Mercury
      produced by several institutions participating in the MESSENGER mission.
      Each DEM data producer applies different techniques to derive their
      products.  The SIS describes each technique in detail.

      The data set contains several global DEM products and some specially
      selected regional DEM products.  Each product are gridded map
      projections of various resolutions and provided in PDS compliant IMG
      format.These gridded map products may contain interpolated values at
      some grid points. Those process by which each product is created is
      described in the SIS.

      Global map products are provided in simple cylindrical projections where
      the raster image extends from 0 to 360 degrees positive east longitudes
      in the sample direction and -90 to 90 degrees latitude extents from
      bottom  to top in the line direction. Polar stereographic projections
      are provided for both the north and south poles. These projections are
      square images that extend from 65 degrees latitude poleward where the
      four centermost pixels surround the pole.  Resolutions vary by product.

      Regional DEM products that highlight certain features on Mercury's
      surface were selected by team members.  These products are provided in
      equirectangular projection with postive east longitudes. Longitude and
      resolution ranges vary by product.

      Dataset projections are given in DEM_EQU_MAP.CAT and DEM_POLAR_MAP.CAT.

      Geospatially labelled, JPEG 2000 format products accompany the USGS and
      DLR DEMs. GeoTIFF format products in the EXTRAS directory accompany the
      ASU DEMs. PDS compliant .LBL files accompany each JPEG 2000
      file. Supporting .XML files accompany the USGS JPEG 2000 products from
      which pixel level information can be read using an appropriate reader.
      The data providers do not provide support for commercially available
      data analysis products.  No internally produced software for the
      visualization or interpretation of data products is provided.

      The file names developed for this PDS archive are restricted to a
      maximum 36-character base name and 3 character extension name with
      a period separating the file and extension names.  Also known as
      the '36.3' format, this is compliant with the ISO 9660 Level 2
      specification (maximum of 40 characters), which is required by PDS.

      USGS DEM PRODUCT IDs are of the form:

        MSGR_DEM_iii_pp_c_Vnn.IMG where

        where:

        iii = producer institution
            USG = U.S. Geological Survey
        pp = projection
            SC = Simple Cylindrical
            NP = North Polar Stereographic
            SP = South Polar Stereographic
            00 = not applicable
        c = product code
            I = image format file
            J = JPEG 2000 file
            S = source product list file
            C = point cloud file
        nn = 2 digit version number


        The following is an example POLAR PRODUCT ID with a description of
        the individual components:

        MDGR_DEM_USG_NP_I_V01

        For this image:
          Producer Institution = U. S. Geological Survey
          Projection = North Polar Stereographic
          Product Code = Image format file
          Version Number = 01

      Regional DLR PRODUCT IDs are of the form:

        MSGR_DEM_DLR_pp_Haa_mm_sss_c_Vnn.ext

        where:

        iii = producer institution
            DLR = German Aerospace Center

        pp  = projection
            EQ = equirectangular
            00 = not applicable
            aa = the IAU-defined quadrangle number on planet Mercury 00-11
        mm  = product type
            DM = primary 16-bit DEM product
       sss = map scale in m/pixel truncated to the nearest integer, '000' if
             not applicable
         c = product code
            I = image format file
            J = JPEG 2000 file
            P = PNG file (if available for EXTRAS directory)
        nn = 2 digit version number

        The following is an example Regional PRODUCT ID with a description of
        the individual components:

        MSGR_DEM_DLR_EQ_H06_DM_222_I_V01

        For this image:
          Producer Institution = German Aerospace Center (DLR)
          Projection = Equatorial
          Covers H06 quadrangle
          Product class = standard 16-bit DEM
          Map scale =  222 m/pixel
          Product Code = Image format file
          Version Number = 01

      Regional ASU PRODUCT IDs are of the form:

        MSGR_DEM_ASU_pp_aaaaabb_mm_sss_c_Vnn.ext

        iii = producer institution
            ASU = Arizona State University
        pp  = projection
            EQ = equirectangular
            00 = not applicable
        aaaaa = designation of the site name that the DEM covers
            bb    = designation of the stereo pair
              = a uniquely numbered integer stereo pair for the site
            MS    = mosaic of the site containing all the stereo paris
        mm    = product type
            DM = primary 16-bit DEM product
            CF = confidence map
            CL = legend associated with the color-shaded relief map
            CS = color-shaded relief map
            OR = 16-bit orthorectified image
            SL = slope map legend
            SM = slope map
            TS = terrain shaded relief map
            RM = readme file (located in INDEX/REGIONAL directory)
        ss    = map scale in m/pixel truncated to the nearest integer, 00 if
                not applicable
         c  = product code
            I = image format file
            T = GEOTIFF file (if available for EXTRAS directory)
            S = source product list file
        nn    = 2 digit version number

      DEM file names are of the form PRODUCT_ID.ttt where:
        ttt = file type
        .IMG = PDS image format
        .JP2 = JPEG 2000 format
        .LBL = PDS label file
        .TXT = ancillary free format text file
        .TAB = ancillary table data file
        .XML = auxiliary file containing XML metadata relating to some
               JPEG 2000 products
        .TIF = TIFF files

Confidence Level Overview
    =========================
      Known issues of concern are described in the DEM SIS.


    Review
    ======
      This archival data set was examined by a peer review panel prior to its
      acceptance by the Planetary Data System (PDS).  The peer review was
      conducted in accordance with PDS procedures.


    Data Coverage and Quality
    =========================
      Descriptions of data coverage and quality are included in the DEM SIS.