ISTAR, the digital cartographic company, has delivered high-resolution colour imagery, high-accuracy digital surface models (DSM), and four separate spectral bands (RGB, NIR) of the Grand Canyon in a single on-time, on-budget mission for the Grand Canyon Monitoring and Research Center (GCMRC). The data was commissioned by the GCMRC to monitor the Canyon’s ecosystem as well as to manage the Colorado River system.
The Grand Canyon’s relief characteristics presented inherent mapping problems that required advanced techniques. Obtaining details and features deep below the canyon walls were the greatest challenges. Escarpment edges seemed impossible to map; shadows and restricted water flow in the dam also hampered operations, restricting mapping to a limited 10-day window. Up until this point, the GCMCR had not found a satisfactory solution or the necessary technology to solve these problems.
In May 2002, ISTAR’s all-digital airborne imaging system was tested and proved the ideal solution. Operating the HRSC-AX multi-line scanner on a Beech King Air Turboprop, ISTAR acquired multi-spectral and panchromatic data and then processed the information with their proprietary technology that automatically merges multiple data sets through a pixel-by-pixel orthocorrection process. The resulting True Orthoimages are geometrically perfect with absolute vertical accuracy meaning the digital imagery is highly detailed and features are represented at their true location. The high operating altitude prevented interference, which allowed the entire project to be completed in the allotted three month time frame. The 1 kilometer wide by 457 kilometer long area was captured in 147 flight lines.
In order to confirm the positive results, the GCMRC deployed traditional surveying methods to serve as a baseline for comparison. Their GIS laboratory determined that “the new all-digital data either met or exceeded our desired program specifications”. They also stated that “based on initial analysis, the entire data sets meets or exceeds these values”. The Water Resources Department of the U.S. Geological Survey (USGS) in Tuscon, Ariz., were the first to use this new data for a field application.
