Environmental Engineering Reference
In-Depth Information
Fig. 2.12 An example of
total station equipment,
which can be used to rapidly
capture precise X, Y, and Z
points
ground or vegetation. In general, the instrument calculates the horizontal and vertical
angles of the aimed laser beam and then calculates the distance to the target by
analyzing the reflected light. It converts the resulting spherical coordinates into X, Y,
Z coordinates for export to a spreadsheet. Although high precision positions can be
used to analyze wetland geometry, the geospatial data are not referenced to any
external vertical or geographic reference frame unless the survey is intentionally
linked into those frameworks by incorporating published benchmarks or local
benchmarks that have been referenced by GPS work. We also note that the use of
reflectorless total stations is not practical in wetlands where the laser would be
reflected from dense vegetation or water rather than the ground.
2.3.2.6 Real Time Kinematic GPS
The RTK GPS is a positioning system that uses two GPS receivers: a base station
and rover (Fig.
2.13
). The base station can be positioned over a local BM to
determine its georeferenced position, or over a published BM with a known
georeferenced position. If the base station is set over a local BM, it should be left
