This product set contains reduced-resolution Interferometric Synthetic Aperture Radar (IFSAR) imagery and geospatial data for the Barrow Peninsula (155.39 - 157.48° W, 70.86 - 71.47° N), for use in Geographic Information Systems (GIS) and remote sensing software. The primary IFSAR data sets were acquired by Intermap Technologies from 27 to 29 July 2002, and consist of an Orthorectified Radar ... Imagery (ORRI), a Digital Surface Model (DSM), and a Digital Terrain Model (DTM). Derived data layers include aspect, shaded relief, and slope-angle grids (floating-point binary format), as well as a vector layer of contour lines (ESRI Shapefile format). Also available are accessory layers compiled from other sources: 1:250,000- and 1:63,360-scale USGS Digital Raster Graphic (DRG) mosaic images (GeoTIFF format); 1:250,000- and 1:63,360-scale USGS quadrangle index maps (ESRI Shapefile format); and a simple polygon layer of the extent of the Barrow Peninsula (ESRI Shapefile format). The DSM and DTM data sets (20 m resolution) are provided in floating-point binary format with header and projection files. The ORRI mosaic (5 m resolution) is available in GeoTIFF format. FGDC-compliant metadata for all data sets are provided in text, HTML, and XML formats, along with the Intermap License Agreement and product handbook. The baseline geospatial data support education, outreach, and multi-disciplinary research of environmental change in Barrow, which is an area of focused scientific interest. Data are available via FTP and CD-ROM.
Quality checks were performed throughout all processing steps. Minimum and maximum domain values were checked for each tile, for merged and mosaicked products. Map extents of separate tiles are correct. Overlaps between tiles are seamless and contain identical values; these were also spot checked for the Barrow Triangle area. Value-added layers and their ranges were quality checked; these ... value-added layers were also used to quality check the values in the DSM. The vertical accuracy of DSMs and DTMs is approximately +/- 1.0 m or better root-mean-square-error (RMSE). Horizontal accuracy is +/- 2.5 m or better RMSE for slopes less than 20 deg. Horizontal accuracy of ORRI data is +/- 1.25 m or better RMSE for slopes less than 20 deg. These accuracy statements depend on the sensor's view of the ground, and are applicable to the height of the first surface return. These statements also assume the surface is devoid of vegetation or continuous roof coverage in urban areas (Intermap 2002). Accuracy statements are based on areas of moderate terrain. Diminished accuracies are to be expected in areas of extreme terrain and dense vegetation. The DSM and DTM contain some small (30 to 50 cm high) ripples or 'corn rows.' The Intermap data collection systems are very accurately calibrated to control the constant differential phase error between the antennae. The calibration ensures that data are within specification; however, on flat terrain, very low-level artifacts are present from uncompensated differential phase errors. Very small periodic DEM ripples in the range dimension occurred at a consistent location in range and are continuous along the strip. High-frequency variation (speckle) exists in both the imagery and terrain data sets. The high-frequency variation in the DEM is a product of the signal-to-noise ratio that decreases from the near to far range across the track; therefore, the noise increases with the distance from the antenna. The difference in noise between the near and far range of the strip can sometimes be seen at the seam where DEMs from two strips are mosaicked together.
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Province or State:
Intermap Technologies, Inc. 2002. GLOBAL terrain product handbook and quick start guide. Englewood, CO, USA: Intermap Technologies Inc. Tennant, J.K., T. Coyne, and E. DeCol. 2003. Star-3i interferometric synthetic aperture radar (INSAR): more lessons learned on the road to commercialization. Calgary, Alberta: Intermap Technologies Corp.