Interferometric Synthetic Aperture Radar - Elevation (IFSARE)
The Interferometric Synthetic Aperture Radar - Elevation (IFSARE) was developed by Environmental Research Institute of Michigan (ERIM), Ann Arbor, Mich., under a Defense Advanced Research Projects Agency (DARPA) project. IFSARE uses interferometric radar on an ERIM-owned LearJet 36A to collect and record data, then process it on the ground into digital terrain elevation models. IFSARE can rapidly generate three dimensional maps accurate to within six feet elevation day or night or in adverse weather conditions. In the past, such maps could take months to create, using satellite and ground surveying techniques. The IFSARE's capability has obvious advantages for military customers, but also has significant commercial potential.
The IFSARE program began in 1992, when DARPA, in partnership with the Army Topographic Engineering Center, determined that there was a need for an airborne, all-weather, day/night, radar- based mapping capability. IFSARE can image large geographic areas with a high degree of terrain height accuracy, an ability that is necessary for the military to produce accurate maps and terrain surveys for military operations. The maps can be produced in either photographic or digital format.
IFSARE uses interferometric radar techniques aboard an airborne platform to collect and record phase history data which is then ground processed into Digital Terrain Elevation Models (DTEMs). A by-product of the DTEM generation is high-quality Synthetic Aperture Radar (SAR) imagery with an image resolution of approximately 3 meters. This image is inherently co-registered with the DTEM. IFSARE employs Differential Global Positioning System (DGPS) to obtain accurately geocoded, rectified data. Using interferometric radar techniques, IFSARE data can be collected in all weather, day/night, and through atmospheric obscurants. The sensor, however, cannot collect phase history data in areas where there is insufficient radar return, such as water bodies and slope-induced shadows. The result is areas of null pixel values over these areas.
Since 1992, the IFSARE has been used in Bosnia for terrain and elevation analysis, and by the Defense Mapping Agency (now the National Imagery and Mapping Agency), the US Geological Survey, the Army Corps of Engineers, and other government organizations.
In response to a request from U.S. Army, Europe, the IFSARE was deployed to Aviano Air Base, Italy. Under contract to Army TEC, ERIM collected IFSARE data over the U.S. sector in Bosnia, as well as the Sarajevo/Gorazda road corridor. This data was provided to TEC in ERDAS Imagine format specifically to support current operations in the region. The data was also provided to the National Imagery and Mapping Agency (NIMA), formerly DMA. NIMA processed and reformated the data to meet Digital Terrain Elevation Data (DTED) specifications. At TEC, the Field Support Office (FSO) used ERDAS Imagine 8.2 techniques to interpolate and fill data holes caused by missing radar return and to resample the data from 32-bit floating point to signed 16 bit and unsigned 8 bit for the DTEM and the imagery, respectively. The data was distributed in UTM projection WGS 84 ready for exploitation by the MSIP.
The IFSARE provides a unique military capability, but no single organization could justify the maintenance costs of full-time ownership of the system. DoD no longer wished to bear the cost of operating, maintaining and upgrading the system to an operational configuration but wished to retain the right to use the system as needed to produce military maps.
On 29 August 199,5 an Other Transaction agreement was signed by DARPA that had been crafted with great flexibility to allow the fullest exploitation of IFSARE's potential. In it, the Government permits ERIM the full use of the radar and technology for commercial use, while maintaining it on demand for military users. ERIM also agreed to repay the Government the cost of replacement (some $6 million) over five years from commercial revenues it expects to generate. Other advantages to the Government include not having to pay for maintenance of the radar for use in national emergencies or to fund improvements (which will be made to support commercial customers). Further, the consortium planned to build more IFSARE's, lowering their unit cost and increasing their availability. This unique technology had already demonstrated benefits to industry through its exploitation and development of a new commercial market. IFSARE showed the advantages and flexibility of Other Transactions through its facilitaization of technology transition development to actual customer use.
Under a February 1997 agreement with ERIM and Intermap Technologies Inc., Englewood, Colo., Intermap acquired exclusive use of the government radar system. In return, Intermap provided DoD with preferred availability and rates, and pay royalties to DoD. ERIM is a non-profit organization with expertise in advanced radar technologies. ERIM and Intermap have a partnership where ERIM develops new radar technologies and Intermap operates the IFSARE system and develops commercial applications. The agreement allows Intermap to commercialize an important military radar technology (interferometric synthetic aperture radar), while maintaining the Department of Defense's low-cost access to the system's capability to produce accurate, detailed maps and digital terrain elevation models. Under the agreement, Intermap took over maintenance and operating costs, and sells commercial mapping services. Intermap's royalty payments based on those sales allow DARPA to recoup its cost of funding the research and development of the IFSARE advanced capability.
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