Data Set Overview : The High Resolution Imaging Science Experiment (HiRISE) is one of the remote sensing instruments on the Mars Reconnaissance Orbiter (MRO) spacecraft that acquires orbital observations of the Martian surface during a two earth-year primary mapping phase. MRO, successfully launched in August 2005, arrived at Mars in March 2006. Following orbit insertion the spacecraft went into an aerobraking period to achieve a 250 x 315 kilometer near-polar orbit suitable for the Primary Science Phase (PSP) mapping that started in November 2006. Since the start of PSP HiRISE has been continuously operating acquiring 10-20 observations per day.  The HiRISE team is responsible for maintaining an updated dataset of the best version of its science data until meaningful changes in data calibration no longer occur and to release data in an appropriate manner for public access including their final deposition to NASA's Planetary Data System (PDS). In carrying out these responsibilities, the HiRISE team creates two types of standard data products: 1) Experiment Data Record (EDR) products and 2) Reduced Data Record (RDR) Products. An additional, derived product is produced from HiRISE stereo image pairs: 3) Digital Terrain Model (DTM) Products. This document describes the DTM standard products.  The Digital Terrain Model (DTM) product is an image file that represent elevations for an area imaged in stereo by HiRISE. The source images are orthorectified using the DTM to produce orthoimages. Both the DTM and the orthoimages are resampled to a standard map projection They are formatted and organized according to the standards of the PDS. The DTM is stored as a standard PDS IMAGE object with an attached label. The orthoimages are stored in the JPEG2000 format accepted by the PDS. The JPEG2000 images are accompanied by a PDS detached label providing supporting information about the observation.  The HiRISE DTM products comply with the PDS standards for file formats and labels, specifically using the PDS image object definition. The DTM image object uses 'IMG' as its filename extension. The PDS label is embedded within the DTM image object. The DTM orthoimage files, formatted according to the JPEG2000 standard, use 'JP2' as their filename extension. They are accompanied by PDS labels; files that have the same name as the image data file but use 'LBL' for their filename extension. The label files provides image data characterization and science metadata information about the observation. Additionally, the ancillary data files that accompany the DTM products and the archive volume structure are in conformance with PDS standards.  DTM orthoimage data are stored in the JPEG2000 ISO/IEC Part 1 standard format (http://www.jpeg.org/jpeg2000/), which was accepted by the PDS standard in October 2005. The JPEG2000 standard offers benefits distinctly advantageous for storage and access to very large images. With HiRISE RDR products reaching sizes exceeding 30,000 x 70,000 pixels the use of JPEG2000 was recognized as a suitable solution for the storage and distribution of these data products. Advantages include excellent compression performance, multiple resolution levels from a single image data set, progressive decompression quality layers, lossless and lossy compression (HiRISE RDR products use lossless compression per the PDS Standard), pixel datum precision up to 38 bits, multiple image components (or bands), and selective image area access. These features are achieved by the use of a sophisticated image coding system based on discrete wavelet transforms (DWT) combined with other coding techniques to generate a JPEG2000 codestream that can be rendered to image pixel rasters using inverse transform algorithms.   Processing : The processing involved in a HiRISE DTM and associated orthoimages is partially automated, but still involves a great deal of manual input. For this reason, it cannot be pipelined as the other HiRISE products are. HiRISE DTMs are being produced at several institutions including HiROC, USGS Flagstaff, NASA Ames and JPL, using the prodedures described here.  The image data that are the starting points for DTM production are the radiometrically and geometrically calibrated individual RED CCDs. They have gone through the normal HiRISE image processing pipeline up to the HiStitch pipeline, as described in RDR_DS.CAT. Generally, the color CCDs are not used for DTM production. The RED CCDs are reprojected into ideal camera space using the ISIS3 (http://isis.astrogeology.usgs.gov/) program noproj. After noproj the individual CCDs are mosaicked together and then converted to 8-bit raw format. The 8-bit raw images are then imported into the commercial software package Socet Set (copyright) by BAE, Inc. to create the DTM. SPICE information for the RED5 CCD is gathered to provide pointing information for the image to be imported into Socet Set (copyright). The stereo pair is then triangulated and controlled to MOLA elevation values, when possible. MOLA tracks are used as the reference points for elevation and horizontal alignment. At equatorial latitudes, sometimes the MOLA tracks do not completely span the HiRISE image footprint. In polar regions, although the MOLA tracks are more densely spaced, seasonal changes in snow/frost coverage create variability on the scale of a few meters. In both of these cases the producer uses their best judgement to tie the HiRISE DTM to the MOLA tracks. Terrain extraction is performed in Socet Set (copyright) using their proprietary algorithms. After the terrain model is produced, it is examined for obvious blunders and artifacts. These are edited to the extent required by the project, but within reasonable time constraints.  Socet Set (copyright) is used to create the orthoimages for each image in the stereo pair. Orthoimages are produced at two resolutions. The first is the full resolution of the original imagery (e.g. 0.25 m for bin1 images). The second is produced at the same GSD as the DTM. A typical HiRISE DTM produced from two bin1 images can have a GSD (or post spacing) of 1m. During the project pre-processing, the stretch parameters to convert from the native 16-bit to 8-bit format are preserved. These parameters are documented in the label as SCALE and OFFSET should the end user wish to restore the full dynamic range of the original image to the derived orthoimage.  The DTM and orthoimages are exported from Socet Set (copyright) to the ISIS3 cube format in order to populate the labels with correct scaling and mapping values for subsequent PDS format conversion and label generation. These products are map projected using the same mapping definitions as the standard HiRISE RDR products.  Additionally DTM and orthoimage product browse, annotated browse, and thumbnail jpeg images are created for HiRISE and PDS Imaging Node web-based distribution services.  Data : Radiometrically and geometrically corrected RED band products are the input source to DTM processing. Two HiRISE images are used, comprising a stereo pair. Stereo imaging is accomplished by rolling the spacecraft off-nadir. The first stereo image acquired typically is a small off-nadir roll. The second stereo image is usually the larger off-nadir roll. Elevations are derived from a priori knowledge of the observation geometry and the degree of cross-track parallax between the two stereo images. Stereo image targeting includes consideration of shadow length and direction, incidence and phase angle. The ideal stereo pair for DTM creation is acquired under similar lighting conditions and with a stereo convergence angle of 15 to 25 degrees.  Ancillary Data : Generation of the DTM products relies on the MRO-project deliveries for the Spacecraft Ephemeris (SPK kernels) and MRO spacecraft pointing files (CK kernels)  Coordinate System & Cartographic Standards : The HiRISE DTM products are compatible with the cartographic standards and mapping conventions used by the HiRISE RDR and MRO CRISM map products. When spatially registering map products produced by the two instrument teams only a translation and scale change are required. The coordinate system used is planetocentric latitude and east positive longitude direction. The planetocentric latitude is the angle from the equator to a point on the surface of an oblate planet. The longitude increases from west to east (left to right). The planetary constants used in the camera model to produce the HiRISE RDR products are obtained from the NAIF SPICE planetary constants kernel pck0008.tpc. The Mars constants of particular importance are the right ascension and declination of the pole, the prime meridian, rotation rate, and radii. The constants used are: BODY499_POLE_RA : ( 317.68143 -0.1061 0. ) BODY499_POLE_DEC : ( 52.88650 -0.0609 0. ) BODY499_PM : ( 176.630 350.89198226 0. ) BODY499_RADII : ( 3396.19 3396.19 3376.20 )  Additionally, the SPICE kernel de405.bsp was used for the ephemeris data for Mars.  Two map projections are used in the HiRISE DTM products: Equirectangular and Polar Stereographic.

Confidence Level Overview :  Known problems are TBD.  Review : This archival data set has been examined by a peer review panel prior to its acceptance by the Planetary Data System (PDS). The peer review has been carried out in accordance with PDS procedures.  Data Coverage and Quality : DTM products are derived products from HiRISE stereo observations that are radiometrically corrected. The observational coverage on the martian surface is dependent on the instrument operating modes of the observation and on the amount of overlap between of the stereo pair. The largest coverage at 300 kilometer spacecraft altitude is about 6 km crosstrack and 37 kilometers downtrack.  During the Primary and Extended Science Phases of MRO operations, HiRISE is expected to acquire well over 1000 stereo pairs. Due to the lengthy and complicated process required to produce DTMs, not all of the stereo pairs will be used to create DTMs. DTMs to be produced are prioritized by scientific usefulness, optimal image quality and appropriate photometric parameters.