WSP01392 - Laserfiche WebLink

Home Browse Search

I I I I I I I I I I, I I I I I I I I I 1998 Duffy Tunnel and Sevens Surveys During July and August of 1998, we used the Pentax PTSIII total station to obtain XYZ .coordinates for two reaches on the Yampa River (Figure 1). The first reach was located approximately 15 miles upstream of Juniper Hotsprings near the Duffy Tunnel diversion. This site is approximately 1.3 km long and 3777 data points were collected. The second site was located adjacent to Cross Mountain Ranch approximately five miles upstream of Cross Mountain Canyon. This site was approximately \.2 km long and was represented by 1900 data points. To make sure that the data collected at each of the sites could be used in future research, a conscious effort was made to tie the surveys into permanent benchmarks. Due to the remote nature of the Yampa study sites, it was determined that the use of existing benchmarks would impractical. In order to place the surveys into a real world reference system, a Trimble GeoExplorer II was used to GPS in at least two benchmarks for each site. The BLM in Craig maintains a base station that was used to differentially correct the GPS data though post-processing. By letting the GPS average the position for each point for I Ominutes and post-processing, it was possible to determine the positions with a horizontal accuracy of approximately 10cm. These positions were then converted into the State Plane 1983 coordinate system with a NAD83 datum using the Colorado North zone. The State Plane coordinate system was chosen because it was the coordinate system of choice for the CD OW and is based on the English unit system, which the PTSIII allows. At each site, one ground control point was selected to be the reference position and other GCP' s were used for determining azimuth and as a rough check on total station coordinates. 17