The nominal ORRI data files are digital representations of the radar response signal. ORRIs consist of a georeferenced pixel for a number of ground positions at regularly spaced intervals.
These ORRI products represent the first reflective surface as illuminated by the radar. Accuracy statements are based on areas of moderate terrain. Diminished accuracies are to be expected in areas of extreme terrain and dense vegetation.
The ORRI data for 7.5-minute by 18-minute units correspond to the USGS 1:63,360 scale topographic quadrangle map series for available areas in the United States. Each 7.5-minute by 18-minute ORRI is based on 1.25m pixel resolution using the Universal Transverse Mercator (UTM) projection. Each 7.5-minute by 18-minute tile provides full coverage with overlap into adjacent tiles.
The original ORRI is unenhanced and may appear dark when viewed. Both the original ORRI and an ORRI with a customized linear stretch enhancement are provided. The stretched ORRI will appear brighter and is easy to view without additional enhancements.
The system is comprised of two X-band radar antennae that collect data simultaneously. The set of acquired data are "interfered" by a digital correlation process to extract terrain height data and geometrically correct radar images. STAR-3i uses post-processed DGPS data, together with precise inertial measurement data, to attain highly accurate positioning control. Precise terrain height and positioning data are enhanced by careful calibration of the baseline separating the two antennae.
The STAR-3i system accuracy has been independently validated by tests conducted by the U.S. Army Topographic Engineering Center, the Institute of Navigation, Stuttgart University and by NASA. A summary of test results are accessible at <URL:http://www.globalterrain.com>.
Project Information NPRA1 Task Order#: 01010C0010 NPRA2 Task Order#: 01010C0029 Project Area: National Petroleum Reserve Alaska Intermap Project Number: 02218 Time of Collection Flight Segment: m356p13s2 Base Stations: Teshekpuk Flight Direction: 0.2986181 Pass Acquisition Start Time (includes GPS week): 368147.1369 Pass Acquisition Start Time (GPS in HH:MM:SS): 6:15:47 Pass Acquisition Start Time (UTC in HH:MM:SS): 6:15:34 Pass Acquisition End Time (includes GPS week): 368972.505 Pass Acquisition End Time (GPS in HH:MM:SS): 6:29:33 Pass Acquisition End Time (UTC in HH:MM:SS): 6:29:20 Pass Acquisition Date: 25-Jul-02 Flight Segment: m356p37s2 Base Stations: Teshekpuk Flight Direction: 0.2909155 Pass Acquisition Start Time (includes GPS week): 39796.71423 Pass Acquisition Start Time (GPS in HH:MM:SS): 11:03:17 Pass Acquisition Start Time (UTC in HH:MM:SS): 11:03:04 Pass Acquisition End Time (includes GPS week): 40534.62238 Pass Acquisition End Time (GPS in HH:MM:SS): 11:15:35 Pass Acquisition End Time (UTC in HH:MM:SS): 11:15:22 Pass Acquisition Date: 28-Jul-02 Intermap Processing AML Version: 1.1.0, 20030206 ISO 9001 Certification No.: A8379 Image Origin (North West Corner) UTM_Easting_(meters): 487860.625 UTM_Northing_(meters): 7808334.375 Image Extents UTM_Easting_(meters): Min. 487860 Max. 500860 UTM_Northing_(meters): Min. 7793135 Max. 7808335