PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT PUBLICATION_DATE = 2017-05-12 INTERCHANGE_FORMAT = ASCII NOTE = "N/A" END_OBJECT = TEXT END MESSENGER Digital Elevation Model March 30, 2017 MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) Mercury Dual Imaging System (MDIS) Digital Elevation Model (DEM) Archive. 1. Introduction This archive contains Digital Elevation Model (DEM) maps constructed from data acquired by the MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) Mercury Dual Imaging System (MDIS) instrument. 2. File Formats This section describes the format of the kinds of files contained in the DEM Archive Volume. Data that comprise the Archive are formatted in accordance with Planetary Data System (PDS) standards. 2.1. Document File Formats Document files with the .TXT suffix exist in the ROOT, INDEX, CATALOG, DOCUMENT, DEM and EXTRAS directories. They are ASCII files which may have attached or detached PDS labels. Lines in a .TXT file end with a carriage return character (ASCII 13) and a line feed character (ASCII 10). This allows the files to be readable under various operating systems. Some documents in the DOCUMENT directory contain formatting and figures that cannot easily be rendered as ASCII text. Therefore, each document is given in Portable Document Format (PDF) as well. Numerous software providers offer free software for viewing PDF files. Documents provided in the DOCUMENT directory in PDF format are also provided in HTML format (.HTM suffix). A subdirectory containing images files included in the HTML (GIF, JPEG, and/or PNG format) accompanies it. 2.2. Tabular File Format Tabular files (.TAB suffix) exist in the INDEX, DEM, and EXTRAS directory. Tabular files are ASCII files formatted for direct reading into many applications on various computers. All fields are separated either by commas or spaces. Records are of fixed-length and character fields are padded with spaces to keep quotation marks in the same columns of successive records. Character fields are left justified, and numeric fields are right justified. The 'start byte' listed in the labels indicate the starting position in bytes of each field in a record; the field length 'bytes' does not include the commas between fields, or quotation marks for ASCII strings. The last two bytes of each record contain the ASCII carriage return and line feed characters. This allows a table to be treated as a fixed length record file on computers that support this file type and as a text file with embedded line delimiters on those that don't. Every DEM tabular file is described by a detached PDS label with the same name as the data file it describes, and the extension .LBL. For example, the file INDEX.TAB is accompanied by the detached label file INDEX.LBL in the same directory. 2.3. PDS Label Format All data files in the DEM archive have detached PDS labels. For examples of PDS labels, see the Data Product SIS in the DOCUMENT directory. A PDS label provides descriptive information about the associated file. The PDS label is an object-oriented structure consisting of sets of 'keyword=value' declarations. The object to which the label refers (e.g. IMAGE, TABLE, etc.) is denoted by a statement of the form: ^object = location in which the carat character (^, also called a pointer in this context) indicates where to find the object. In an embedded label, the location is an integer representing the starting record number of the object (the first record in the file is record 1). In a detached label, the location denotes the name of the file containing the object, along with the starting record or byte number, if there is more than one object in the file. For example: ^HEADER = ("F01.IMG",1) ^IMAGE = ("F01.IMG",1025 ) indicates that the IMAGE object begins at byte 1025 of the file F01.IMG, in the same directory as the detached label file. Below is a list of the possible formats for the ^object definition. ^object = n ^object = n ^object = "filename.ext" ^object = ("filename.ext",n) ^object = ("filename.ext",n) where n is the starting record or byte number of the object, counting from the beginning of the file (record 1, byte 1), indicates that the number given is in units of bytes, filename is the up to 36 character, alphanumeric upper-case file name, ext is the 3 character upper-case file extension Lines of text in detached labels end with a carriage return character (ASCII 13) and a line feed character (ASCII 10). This allows the files to be readable under various operating systems. 2.4. Catalog File Format Catalog files (suffix .CAT) exist in the ROOT and CATALOG directories. They are text files formatted in an object-oriented structure consisting of sets of 'keyword=value' declarations, so that they are readable by humans and by software. 2.5. Science Data File Formats The science data products are provided as image (suffix *.IMG) files and as JPEG 2000 (suffix *.JP2) files. IMG Files: The *.IMG files contain the full, uncompressed, unreduced DEM data and are the primary science products in this volume. They are accompanied by full detached PDS labels that describe their formatting and contents. See the Software Interface Specification (SIS) document included in the DOCUMENT directory of this volume for a full description of these and supporting products. JPEG 2000 Files: Some of the DEM data are provided in JPEG 2000 (*.JP2) format. These products follow the JPEG 2000 standard and should be readable by most modern image viewing software. They are also accompanied by detached PDS labels that describe their contents. 3. Archive Contents Files in this archive are organized into a series of subdirectories below the top-level directory. The archive organization and the contents of each directory are described below. _________________________________|______________________________ | | | | | | | ___________________________|_____________________________ |________ | | | | | | | | | | | ____|____ | ____|____ ____|____ | | | | | | | | | | | | | | | | | | | _____________________________| | | | Top-level (root) Directory --------------------------- AAREADME.TXT The file you are currently reading. ERRATA.TXT This text file content describes known anomalies and errors along with additional comments and updates concerning the archive volume. VOLDESC.CAT This text file contains a description of the volume contents as a PDS catalog object. It is a required file on PDS archive volumes. CATALOG Directory ----------------- The files in the Catalog directory provide a top-level understanding of the mission, spacecraft, instrument, and data set. The files in this directory become part of the PDS Catalog to provide background information for the user searching for data. Their format and contents are further specified in the PDS Standards Reference. CATINFO.TXT Identifies and describes the function of each file in the catalog directory. MDIS_DEM_DS.CAT DEM data set description. INSTHOST.CAT Description of the MESSENGER spacecraft for the PDS catalog. MDIS_NAC_INST.CAT, MDIS_WAC_INST.CAT Description of the MDIS NAC and WAC instruments for the PDS catalog. (The DEMs are produced from MDIS data.) DEM_EQU_MAP.CAT DEM data set map projection information for equatorial region. DEM_LMBRT_MAP.CAT DEM data set map projection information for quadrangle products provided in Lambert Conformal projections. DEM_POLAR_MAP.CAT DEM data set map projection information for polar region. MISSION.CAT Description of the MESSENGER mission for the PDS catalog. PERSON.CAT List of personnel who may be contacted for information about the DEM data volume. REF.CAT Catalog objects' citation list for the PDS catalog for the whole MESSENGER mission. DEM Directory -------------- The DEM directory contains the Digital Elevation Model products. It contains three subdirectories, GLOBAL, POLAR and REGIONAL. GLOBAL Directory The GLOBAL directory contains the global DEM products provided by the USGS. Global DEMs cover large sections of the planet Mercury. These are equatorial DEMs that are centered on the planetary equator and wrap around the planet's equator extending northward and southward. The GLOBAL subdirectory contains an IMG and a JPEG2000 subdirectories. All global DEMs are provided in PDS image (*.IMG) and JPEG 2000 (*.JP2) formats in simple cylindrical map projections. IMG Subdirectory The IMG directory contains the full image (*.IMG) files and some supporting .TXT and .TAB files, a format file .FMT and their detached PDS labels. JPEG2000 Subdirectory The JPEG2000 directory contains the files in JPEG 2000 format along with their PDS labels and supporting files. The supporting files include XML formatted metadata files. POLAR Directory The POLAR directory contains the polar DEM products provided by the USGS. The polar DEMs are centered on the planet's north or south poles and extend southward or northward depending on the pole. The POLAR subdirectory contains an IMG and a JPEG2000 subdirectories. All polar DEMs are provided in PDS image (*.IMG) and JPEG 2000 (*.JP2) formats in polar stereographic map projections. IMG Subdirectory The IMG directory contains the full image (*.IMG) files and their detached PDS labels. JPEG2000 Subdirectory The JPEG2000 directory contains the files in JPEG 2000 format along with their PDS labels and supporting files. The supporting files include XML formatted metadata files. The USGS filenames in the GLOBAL and POLAR directories have the following naming convention MSGR_DEM_USG___V. where: is the projection type: SC: simple cylindrical NP: North Polar Stereographic SP: South Polar Stereographic 00: not applicable is the product code: I: DEM product in IMG format J: DEM product in JPEG2000 format S: source product list file C: point cloud file is the product version number REGIONAL Directory The REGIONAL subdirectory contains regional DEM products provided by ASU. The regional DEMs are centered on a particular feature on the planet and cover the surrounding region. The size of the area that they cover varies. The regional DEMs provided in this volume do not collectively cover the whole of Mercury. All regional DEMs are provided in in equirectangular map projections in PDS image (*.IMG) format. Associated GeoTIFF files and metadata are provided in the EXTRAS/REGIONAL directory. IMG Subdirectory The IMG directory contains the full image (*.IMG) files and their detached PDS labels. See the EXTRAS/REGIONAL directory in this volume for supplemental GeoTIFF images and metadata associated with the ASU DEMs. The ASU filenames in this directory have the naming convention MSGR_DEM_ASU______V. Where: is the projection type: EQ: equirectangular 00: not applicable designation for the site name that the product is centered around number of the stereo pair product type designation DM: primary 32-bit DEM product CF: confidence map CL: legend associated with the color-shaded relief map CS: color-shaded relief map O1: 16-bit orthorectified image, image 1 O2: 16-bit orthorectified image, image 2 NOTE: The "O" in the above are capital letter Oh, not zero. SL: slope map legend SM: slope map TS: terrain shaded relief map RM: readme file is the map scale in meters/pixel truncated to the nearest integer, "00" if not applicable is the product code: I: DEM product in IMG format T: GeoTiff format image S: source product list file is the product version number QUAD Directory The QUAD subdirectory contains the quadrangle-based DEM products provided by DLR (German Aerospace Center). The DEMs provided by DLR cover four selected quadrangles of the Mercury surface as defined by Greely & Batson (1990) [GREELY&BATSON1990]. These are the quadrangles H03, H05, H06, and H07. They do not cover the entirety of the planet Mercury. These DEMs are provided both as PDS image (*.IMG) files and as JPEG2000 (*.JP2) formatted files. The products are provided in equirectangular, simple cylindrical, and Lambert Conformal projections, depending on the product. Associated GeoTIFF and PNG format images are provided in the EXTRAS/QUAD directory. IMG Subdirectory The IMG directory contains the full image (*.IMG) files and their detached PDS labels. JPEG2000 Subdirectory The JPEG2000 directory contains the files in JPEG 2000 format along with their PDS labels and supporting files. The supporting files include XML formatted metadata files. See the EXTRAS/QUAD directory in this volume for supplemental GeoTIFF and PNG images associated with the DLR DEMs. The DLR filenames in this directory have the naming convention MSGR_DEM_DLR__H_DM___V. Where: is the projection type: EQ: equirectangular SC: simple cylindrical LC: lambert conformal is the quadrangle number is the map scale in meters truncated to the nearest integer is the product code: I: DEM product in IMG format J: DEM product in JPEG2000 format T: GeoTiff format image P: PNG format image is the product version number Filename Extensions The names of all products in this volume have a three-character file extension is the file extension indicating file type IMG = PDS image file TAB = text table file TXT = free format text file JP2 = JPEG 2000 image TIF = GeoTIFF image PNG = Portable Network Graphics (PNG) format image XML = USGS auxiliary (AUX) file with XML metadata useful for displaying JPEG2000 images with GDAL tools LBL = PDS label file Files ending *_AUX.XML contain JPEG2000 metadata. NOTE: It may be necessary to rename files ending *_AUX.XML to *.aux.xml prior to use with GDAL-based tools. DOCUMENT Directory ------------------ The DOCUMENT directory contains documentation to help the user understand and use the archive data. DOCINFO.TXT Identifies and describes the function of each file in the document directory. MSGR_DEM_SIS.PDF Software Interface Specification for the DEM data products as an Adobe PDF document. MSGR_DEM_SIS.HTM Software Interface Specification for the DEM data products as an HTML document. There is also an IMAGES directory within the DOCUMENT directory that contains the image files (GIF, JPEG, and/or PNG format) that are included by the HTM file. MSGR_DEM_SIS.LBL PDS label for MSGR_DEM_SIS.PDF and MSGR_DEM_SIS.HTM and image files. EXTRAS Directory ---------------- The EXTRAS directory contains miscellaneous other materials that the user may find useful, but that are beyond the scope of the required elements of this archive. This directory contains two subdirectories, ISIS and REGIONAL. The ISIS subdirectory contains products produced by the USGS ISIS software that might be useful in analyzing the USGS global and polar DEM products. The REGIONAL subdirectory contains information that might be useful in analyzing the regional DEM products and possibly more importantly, GeoTIFF images relating to the ASU products. See the file EXTRAS/EXTRINFO.TXT for more information. INDEX Directory --------------- The INDEX directory contains PDS index files for this archive. An index file is an ASCII table with each record (or line) in the table containing information about a single data product in archive. Files in the Index directory are provided to help the user locate products on the archive volume. INDXINFO.TXT Identifies and describes the function of each file in the index subdirectory. This includes a description of the structure and contents of the index table and usage notes. INDEX.TAB The image index file is organized as a table: there is a row for each map tile image on the volume; the columns contain the image and mapping parameters. Information includes map projection type, resolution, and map extents in latitude and longitude. INDEX.LBL Detached PDS label for INDEX.TAB that describes its organization and contents. MD5.TAB The hash table. The hash table is a listing of all files in the archive (with the exception of the hash table itself) that gives the MD5 hash value (message digest) for the file and the full path including file name. It is generated by the commonly available 'MD5Deep' utility. This file is useful as a manifest for the archive and for data integrity assurance. MD5.LBL Detached PDS label for MD5.TAB that describes its organization and contents. 4. Additional Mercury DEM Products at PDS Geosciences Node An additional set of northern-hemisphere DEM products (gridded data record (GDR)) produced from MESSENGER Mercury Laser Altimeter (MLA) data is available at the PDS Geosciences Node in the MESS-E/V/H-MLA-3/4-CDR/RDR-DATA-V1.0 dataset in the MESSMLA_2001 volume. 5. Whom to Contact for Information For questions concerning this volume set, contact: PDS - Flagstaff Imaging Node United States Geological Survey 2255 North Gemini Drive Flagstaff, AZ 86001 Electronic mail address: pdsmgr@usgs.gov WWW Site: http://pds.jpl.nasa.gov/ E-mail: pds_operator@jpl.nasa.gov 6. Cognizant Persons This archive volume was designed and produced by Kris J. Becker of the US Geological Survey (USGS) in Flagstaff, Arizona and by Susan Ensor and Mike Reid of the Johns Hopkins Applied Physics Laboratory (JHU/APL) in Laurel, Maryland. Data products were produced and provided by teams led by Kris J. Becker of the USGS, Mark Robinson of Arizona State University (ASU), and Frank Preusker of the German Aerospace Center (DLR). The original MDIS data from which the DEM products were created were produced by Christopher Hash and Erick Malaret of Applied Coherent Technology, Inc. (ACT) in Herndon, Virginia. This archive volume is managed by Patricia Garcia of the NASA Planetary Data System (PDS) Imaging Node at the USGS in Flagstaff, Arizona. Please see the PERSON.CAT file in the CATALOG directory of this volume for additional contact information.