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has the least amount of low velocity habitat area. Any habitat in this reach occurs between where the river emerges from Raplee Ridge anticline and Mexican Hat, Utah. Video Acquisition Acquisition of the airborne videography for this study is done using the Reclamation Bell Jet Ranger helicopter based in Salt Lake City, Utah. The use of a helicopter allows for flat turns so that the camera remains vertical, reducing one source of error. A Sony DXC M7 CCD video camera with a 12:1 zoom lens set at full wide angle is mounted on the underside nose of the helicopter with a Tyler remote controllable mount. The recording deck is a Sony 3!4-inch VO 8800, U-matic SP. The helicopter is equipped with a radar altimeter to allow the pilot to maintain a constant altitude above the river.' Prior to the video acquisition mission, ground reference measurement points are set up. These points take the form of either target panels placed a known distance apart near the river, or bridges that cross the river which are measured to give a known ground length. San Juan videography is acquired at an altitude of 2,000 feet above the river. This altitude allows for full bank coverage with one pass for the majority of the river. A flying height of 2,000 feet results in a scale of about 1:2260 for the videography, as viewed on the computer monitor. As an aid to interpretation, the video analyst rides in the helicopter at the time of acquisition. The analyst views the taped scene with a small black and white monitor during the flight and records comments onto the audio track. Because of the size and quality of the flight monitor, these taped comments provide important ground information that may only be evident when viewed with the eye during the flight. An example of this information might be shallow water areas that may not be discernible from wet sand when viewed on the tape. Another use for the audio commentary is to periodically give an altitude reading from the radar altimeter, especially when more than a 100-foot deviation from nominal altitude occurs. In the laboratory, audio information can be used to make calibration adjustments to the captured video frames. Image Processing The videographic tape is then analyzed/interpreted using PC based MIPS (Map and Image Processing System) software which has video frame capture capability. The tape is viewed using a Sony VP-9000 video tape player that is connected to a 19-inch color monitor and the computer video capture board. The analyst runs the video tape and, at the desired point in the tape, captures a video frame with the software set in the video frame capture mode. The aspect relation of the computer monitor lines/cohunns is then corrected to give square pixels. The video frame is now in a digital raster form that can be stored and interpreted with other software functions. The raster pixel size is now ready to be calibrated using the ground reference features. A frame containing a bridge or calibration panels is captured and a caliper tool is placed over the known distance with a mouse. The pixel size for the entire raster is then set by entering the dimension of the feature. This calibration is then used for the following captured frames until the calibration is changed because of flying height change. The 2,000-foot flying height yields a pixel size of I-meter ground distance on a side. Habitat areas are then delineated on screen with a planimeter function that computes the area of a polygon made with a cursor positioned by a mouse. The software produces an ASCII text file containing labels and 3