Digital Point Positioning Data Base (DPPDB)
The Digital Point Positioning Database (DPPDB) is a stereo image based product developed by NIMA and introduced in the mid-1990s. The DPPDB product consists of parametric support data, compressed reference graphics, and high resolution national imagery stereo pair sets covering a nominal 60 nautical mile (NM) by 60 NM area. It can be exploited on a stereo equipped digital imagery workstation using DEWDROP (NIMA-provided exploitation software) or RAINDROP and enables rapid readout of coordinates and associated accuracy. DPPDB replaces the film-based Point Positioning Database (PPDB). DPPDB with RAINDROP may be hosted on a Sun Sparc or a PC. The DPPDB is distributed on 8 mm tape and conforms to the National Imagery Transmission Format Standard (NITFS). To provide NIMA the capability to mass-produce DPPDBs, the Point Positioning Production System (PPPS) was developed as an augmentation to NIMA's Digital Production System (DPS).
The Point Positioning Data Base (PPDB) was an important and widely used imagery-based product, originally developed by the Defense Mapping Agency (DMA)during the Vietnam era to support B-52 and F-111 weapons and navigation systems. PPDBs, in various forms, are routinely used by military and intelligence services for precise coordinate derivation to support targeting and mission planning. The hardcopy, video, and digitized versions of the PPDB were phased out of production and are being replaced by the Digital PPDB (DPPDB) beginning in 1995.
The military and intelligence services routinely use PPDBs for precise coordinate derivation to support the targeting and mission planning requirements of a variety of weapons systems. It is called a data base because it is made up of several dependent components: rectified aerial imagery and the support data needed to exploit that imagery. Its primary purpose is to allow the user to derive the precise coordinates (latitude, longitude and height) of any identifiable point or target contained within the product area.
The original PPDB, or hardcopy PPDB, was developed during the Vietnam era to support B-52 and F-111 weapons and navigation systems. The hardcopy PPDB consisted of many separate pieces of film (termed "chips") comprising a number of stereo models, a data cassette or floppy disk containing support files, and software. The PPDB also included a reference manual with graphics that served as an index for the film chips. This product was exploited on a deployable analytical stereocomparator, the Analytical Photogrammetric Position System (APPS) stereocomparator and an integrated Hewlett-Packard calculator or computer.
The video PPDB (VPPDB) was developed in the late 1980s to address problems associated with the hardcopy version. The users needed a simple and quick softcopy system. The process of setting up the APPS, handling the film, and taking the measurements required to derive point coordinates may consume up to 15 minutes per point. Additionally, the APPS operator required significant training and frequent practice to maintain proficiency.
The VPPDB is composed of maps and monoscopic imagery that have been transferred to a 12-inch analog video disk. Digital Terrain Elevation Data (DTED) was provided on a CD-ROM and exploitation data on a diskette. The exploitation system was a FULCRUM Videomap system that is hosted on a 80386 PC. The system used monoscopic imagery to compute latitude and longitude, but relied on DTED to determine elevation. Therefore, VPPDB-derived elevations were not as accurate as those derived from hardcopy PPDBs.
In response to demands from the military for an all-digital precise positioning product, DMA developed and produced the Digitized PPDB. The Digitized PPDB was intended to be integrated directly into targeting and mission planning systems. It was produced by digitizing hardcopy PPDBs. It was distributed on a Very Large Data Storage (VLDS) cartridge containing uncompressed 8-bit stereo imagery and support data files. Because of the extremely large amounts of imagery to be processed (20 GB or more), users required minicomputer or mainframe computer systems for exploitation.
The video and digitized versions of the PPDB are no longer being produced. The hardcopy PPDB was phased out of production in 1994. Beginning in 1995, DMA began producing the new Digital PPDB (DPPDB). Because of its relationship to national security, the DPPDB, like the previous versions, is only be available to qualified DOD and intelligence service users.
The areal coverage of a standard DPPDB is based on a fixed global 60 nautical mile grid. This 60 x 60 nautical mile rectangle is termed a product rectangle. During crisis situations and to support special operations, ad hoc DPPDBs can be produced which can be smaller than a product rectangle.
The DPPDB is composed of three parts: (1) exploitation support data, (2) a digital reference graphic, and (3) compressed stereo panchromatic imagery. The DPPDB is distributed on 5 Gigabyte (GB) 8 mm tape and conforms to the National Imagery Transmission Format Standard (NITFS) Version 2.0. The nominal compressed size of a DPPDB is 4 GB. The expanded data set requires from 26 to 30 GB of storage space.
Exploitation support data is the non-image information that describes the product and is essential for the use of the DPPDB. DPPDB exploitation support data is contained in every file on the product tape. Exploitation support data consists of the following kinds of information:
- DPPDB stock number
- Classification, handling instructions, and downgrading instructions
- Product footprint vectors
- Segment footprint vectors
- Adverse area and void area information
- Absolute and relative accuracy data
- Rational function coefficients
- Rectangle and model shear evaluations
- Diagnostic point coordinates
- Correction data for converting elevations from the datum ellipsoid to mean sea level
The reference graphic provides the user with a digital map of the product area. Its intended use is for orientation, as a base for displaying various vector overlays, and for identifying the rough location of a target. The graphic is an 8-bit color raster image covering an area slightly larger than the product rectangle. The source of the reference graphic is DMA Compressed ARC Digitized Raster Graphics (CADRG) data. In addition to being compliant with NITFS, the reference graphic also complies with DMA's Raster Product Format (RPF).
The source imagery for the DPPDB is controlled to WGS-84 through a block triangulation process on the NIMA Digital Production System. It is rectified to simplify stereo viewing on both the NIMA production system and the user's exploitation systems. It is enhanced by applying a Dynamic Range Adjustment (DRA), or contrast stretch. A Modulation Transfer Function Compensation (MTFC) filter is applied to produce a mild edge sharpening effect. Finally, the 8 bits per pixel (bpp) imagery is compressed using the Joint Photographic Experts Group (JPEG) Discrete Cosine Transform (DCT) bandwidth compression algorithm with a quality factor of between 70 and 80. This reduces the data to a range of 0.6 to 1.4 bpp.
There are two complete sets of stereo panchromatic imagery provided on the product: a full resolution data set, and a 1/8X reduced resolution image set, also called the overview image. The imagery covers the entire product rectangle and overlaps adjoining rectangles by a minimum of 2000 feet (ground distance). A rectangle is composed of several image models. Each image model is further divided into segment models. Coincident overview image models are segmented in the same way as the full resolution models. Secondary imagery, used for gapfill or to provide coverage for cloud-filled areas in the primary imagery, is segmented in a similar fashion. Segment-to-segment overlap is also maintained at a minimum of 2000 feet.
The standard distribution media for the DPPDB is an 8 mm tape cartridge. Occasionally, more than one tape will be needed to store a single product rectangle, but a standard DPPDB will never encompass more than two tapes. The DPPDB is a series of files that are arranged in a particular sequence on the product tape. Each file conforms to the NITF 2.0 standard.
DPPDBs are used in various ways by the different users depending on their particular mission. The DPPDB is used by deployed Department of Defense (DOD) users to support mission planning, targeting, and weaponeering functions. The DPPDB provides critical positioning support to aircraft that use radar navigation systems, such as the B-52, F-111, and B-1. Operational autonomous weapons, such as the Air Launched Cruise Missile (ALCM) and the Tomahawk Sea Launched Cruise Missile (SLCM), will use precise coordinates derived from DPPDBs. The DPPDB (1) provides enhanced absolute accuracy for GPS/INS guided weapons, (2) provides improved relative and absolute positioning for sensor guided weapons, and (3) reduces mission planning time for autonomous weapons.
Delivery occured at the DMA Hydrographic/Topographic Center (DMAHTC) in Maryland and the DMA Aerospace Center (DMAAC) in St. Louis in late 1994. The production program called for the initial production to begin in January 1995. By FY97, DPPDB production ramped up to a full production capacity of 600 rectangles per year.
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