Environmental Engineering Reference
In-Depth Information
Fig. 2.15 ArcGIS map of
Molera Wetland with the
survey points
Approximately 270 positions were shot using RTK GPS during one afternoon at
Molera Wetland (Fig.
2.15
). The base station was placed on a known benchmark.
The survey focused on the pond edges because they were more complex than the
central part of the wetland pond. In ArcMap, we drew a polygon around the pond
perimeter and used the 188 points inside the polygon in the following geometric
analysis. Next we entered the data into a spreadsheet with columns labeled “East-
ing”, “Northing”, and “Elev”. In general, those columns can also represent any X, Y
positioning system that was used in the survey, including an arbitrary local survey
framework.
In some cases, one must make vertical or horizontal adjustments (e.g., adjust the
Z value to relate to stage or NAVD88 for example). We used the GPS system to
provide output in WGS 84 UTM, Zone 10 North meters as the horizontal reference
and NAVD88 meters as the vertical reference, so no further adjustments were
required.
