A Cornerstone for HQ U.S. Army Europe
|Figure 1 Total Vector Extraction using Commercial Satellite Imagery and ESRI’s ArcGIS Production Line Tool Set (PLTS)|
Theater Geospatial Database
U.S. Army Europe
The Theater Geospatial Database (TGD) provides the U.S. Army with a highly flexible geospatial data generation and distribution capability organic to each major Army command. The TGD concept was born from a grassroots effort within the U.S. Army geospatial community to meet shortfalls in tacti-cal and urban-level geospatial data creation, management and dissemination that are vital to the warfighter on the ground. The TGD was designed to complement National Geospatial-Intelligence Agency’s (NGA) geospatial production, providing an in-theater, mission-specific geospatial data generation, management and dissemination capability.
Each major Army command operates its own TGD — U.S. Army Pacific, U.S. Army Europe (USAREUR) and U.S. Army Central Command. The TGD offers each major command a flexible and responsive geospatial production asset that can keep pace with con-stantly changing operational and geospatial data requirements of the Army. With a production plan that can be set, controlled and priori-tized at the major Army command level, the TGD can meet local geospatial production requirements with rapid response.
National-level agencies provide excellent global and strategic-level geospatial data and support programs to the Army commands, but cannot meet all of the tactical and urban geospatial data needs for all levels of Army operations. This is especially true today, with national geospatial pro-duction assets focused on operations in Iraq, Afghanistan and the Global War on Terror. The TGD capability at HQ USAREUR allows the local commander to direct geospatial data and product generation with rapid turn-around time for the completion of finished geospatial and terrain analy-sis products. This flexible response capability makes the USAREUR TGD a critical asset to the local commander to gain an up-to-date, mission-specific geospatial picture of the battlefield.
Today’s military operations, especially in the USAREUR area of responsibility, take place in joint and multi-national environments. Pro-viding geospatial data and products to a wide range of military customers and coalition partners requires unclassified sources for geospatial data and product generation. The USAREUR TGD typically utilizes commercial satellite imagery to meet or facilitate this requirement. Com-mercial satellite imagery provides a high-resolution and accurate source that can be used to generate geospatial data and non-standard map products that are both unclassified and releasable to foreign partners.
|Figure 2 Topographic Line Map (TLM) produced at the USAREUR TGD|
Commercial satellite imagery (CSI) is well suited for the TGD production mission. CSI provides excellent wide-area coverage and the low-nadir angle collection capability required to generate accurate imagery mosaics for vector data extraction. The USAREUR TGD routinely tasks commercial satellites to collect data over USAREUR areas of interest, and CSI provides an alternative source to utilizing national assets that can often be unavailable due to competing intelligence and geospatial requirements. The USAREUR TGD executes CSI purchases or tasks CSI collections through the U.S. Army Topographic Engineer Center (TEC) located at Fort Belvoir, Virginia. The TEC, as the Army’s Executive Agent for CSI, utilizes the NGA ClearView commercial imagery contract with U.S. vendors to purchase CSI. The imagery is delivered to the TGD, and copies are provided to the Unclassified NGA Image Library (UNIL) for other Department of Defense (DoD) users to access. Once purchased by an organization with the appropriate license, commercial imagery in the UNIL is free to all DoD organizations through the ClearView license agreement.
Commercial imagery production at the USAREUR TGD requires significant up-front planning to avoid unnecessary purchases of imagery and to ensure that archived commercial scenes in the UNIL meet photogrammetric and project requirements. The TGD analysts first check the UNIL for imagery that can be used free of charge to cover project footprints. Commercial vendor archives are then checked for suitable source, and if no source is available, a collection of new imagery is requested from the vendor. USAREUR TGD project guidelines are to select images for a triangu-lation project that have a less than 20 degree off-nadir angle, have less than 10% cloud cover and have been acquired in the last two years. For pro-jects with a tight schedule, classified national imagery sources will be considered, but the use of this type of source can limit the release of subse-quently produced data or maps. Commercial imagery is therefore always preferred over national sources since it is unclassified, the data extracted from it is unclassified, there is less tasking competition and it is photogrammetry ready.
The TGD typically produces panchromatic image mosaics in either BAE Systems’ Socet Set or Leica Photogrammetry Suite (LPS) software. Control for triangulation is normally identified using controlled government source, when available. If no government control is available, a relative orientation is performed using only tie points in the block adjustment. Accuracy from a large relative block adjustment of commercial imagery nor-mally meets or exceeds accuracy required to produce a 1:50,000 scale tactical level Army geospatial product. The USAREUR TGD standard imagery production processes use the rigorous math model in Socet Set to perform block triangulation, although Rational Polynomial Coefficient (RPC) trian-gulations are performed when mixed source mosaics are created and math models are not provided by the imagery vendor.
|Figure 3 Commercial Image Map produced at the USAREUR TGD|
Triangulated images from the block adjustment are ortho-projected onto the best elevation model available in the area of the project. For most remote locations where the Army operates, only Shuttle Radar Topography Mission (SRTM) 30-meter posting data are avail-able. SRTM data requires significant quality control checks prior to use, as many SRTM data sets may contain data voids caused by terrain masking or other anomalies. Data voids are filled with interpolated values using lower resolution elevation source, such as 100-meter posting Digital Terrain Elevation Data (DTED) Level 1 or other manual editing techniques. The ortho-projected scenes are mo-saicked together using Socet Set based on automatic radiometric stitch line generation processes or manual stitch line generation.
TGD does not routinely utilize Multi-Spectral Imagery (MSI) in the block triangulation process. If MSI is required for the subsequent vector ex-traction or other end product, analysts will warp the MSI to the controlled panchromatic imagery mosaic using LPS. The USAREUR TGD has used MSI in vector extraction projects to identify large landform and vegetation features, primarily in desert regions. For extraction of these types of fea-tures, it is not necessary to block triangulate the MSI source. The TGD is exploring methods to utilize ortho-ready, pan-sharpened commercial im-agery data to exploit high resolution color imagery in production operations. Analyses will be performed to determine the cost benefits of this type of imagery source.
Commercial imagery mosaics generated at the USAREUR TGD can end up in multiple projects, databases and maps. The primary use for im-agery at the TGD is to feed vector data production into regions where little or no tactical level vector data exists. The TGD GIS team typically uses sub-meter panchromatic imagery mosaics to digitize operationally relevant features into the TGD Arc Spatial Data Engine (ArcSDE) tactical-level vector database. Vector extraction from commercial source is done at 1:5,000 scale from commercial panchromatic imagery mosaics to produce a 1:50,000-scale end map product (figure 1).
|Figure 4 Gridded Airfield Graphic using Commercial Satellite Imagery from DigitalGlobe|
The TGD imagery is often a product in itself for USAREUR customers and serves as a background for several USAREUR planning and terrain visu-alization systems. The TGD-generated commercial imagery mosaics are also provided to HQ European Command (EUCOM) for inclusion in their Google Earth environment operated on a government-only network. All commercial imagery mosaics are processed into Controlled Image Base (CIB) 1-meter resolution products for use in Falcon View software or other end user, government-owned terrain visualization software.
From controlled commercial source, the USAREUR TGD generates tactical level vector data and subsequently publishes 1:50,000-scale military Topographic Line Maps (TLM) (see figure 2). The TGD TLM products are similar to NGA standard products, but contain slightly less content and require a fraction of the time to produce. Where TLM products are produced, the TGD will generate 1:25,000-scale panchromatic image maps from the commercial imagery mosaic. These products contain contour lines generated from digital elevation data, and match the geographic areas of the TLM maps (figure 3). Commercial imagery is also used as a background for special products such as airfield graphics or other topical map products (figure 4). Because they are produced from commercial satellite imagery, these products can be created at the unclassified level, allowing for maximum distribution throughout U.S. and coalition forces.
Commercial satellite systems provide the USAREUR TGD with an excellent source of unclassified, high-resolution imagery that is specifically designed for mapping applications and is perfectly suited to support our joint and coalition support missions. The TGD-produced imagery mosaics are provided to coalition partners who often don’t have the resources to acquire or produce them themselves. These products often promote synergy and goodwill among USAREUR and coalition partners, and allow for an unclassified, releasable common geospatial operating picture. The USAREUR TGD will continue to utilize commercial satellite imagery in future operations and we look forward to the new generation of high-resolution commercial satellites coming under the NGA NextView contract.
Note: This article discusses the use of commercial satellite imagery at the USAREUR TGD, and does not speak for all Army TGD sites.