Instructions
for Setting up GPS and Topcon for Stream Surveys
I. Walk the length of the sample reach. Place flagging at each 10m segment to be used for algal sampling, assessing riffle-pool-run ratios, etc. While doing this, assess locations within the stream or along the bank that can be seen from a large portion of the sample reach. You are looking for two types of positions:
1. Topcon stations. These must have line of sight/visibility of a
number of cross-sections and thalweg or other desired features.
2. GPS reference points. Must be visible from maximum number of Topcon stations.
II.
Establish a base station with the GPS. This should be visible from the
downstream segment being surveyed and as far upstream as possible. Begin
collecting GPS data.
A. Select point.
B. Set up tripod. Plumb antenna pole. Attach antenna. Attach coaxial cable from bag holding receiver to antenna.
C. Attach data logger to cable in from pouch of receiver bag.
D. Turn on unit. Check battery status. Press "Enter" when
"Data Collection" is highlighted from main menu. Either create
or reopen a rover file. Confirm antenna height is 2.05m. Create a point_generic feature. Enter comment, e.g. "GPS reference pt 1",
before collecting data.
E. When finished collecting points, redo steps A-D as appropriate to
create a "turning point" (Figure 5.14b from Gordon). You will
need a fore sight and back sight of the current GPS reference point from
the current and next Topcon positions.
III. Set up Topcon where you can get at least one full cross-section and some thalweg slope measurements.
A. Level instrument; don't try to level in 4 directions- just 2 at 90 degrees to each other.
B. Zero the Topcon's horizontal angle on the reference beacon by
pushing "0Set" on the instrument twice, once the horizontal
angle is set at the desired position and locked. You may have to exit the
measurement mode by pressing "Ang%" on the instrument's front
panel.
Be sure to sight the GPS beacon from the current and next Topcon positions (Figure 5.14b from Gordon).