Spectra Precision Survey Pro v5.4 - Manual (Page 79)

69
Collecting Elevations
in an Open Level Loop
Description of a Simple Level Loop
A simple level loop is illustrated below.
Collecting elevations in a simple level loop consists of the following:
1. In every level loop, you will start with a backsight observation to the opening
CBM.
2. You will observe some number of turning points next. Turning points are not
stored in the survey file. They are used as intermediate points to transfer
the elevation between benchmarks.
3. After some number of turning points, you will reach a point you wish to
store an elevation for. You will observe this point as a benchmark. You can
observe a brand new point as a benchmark, in which case a new point with
only an elevation coordinate will be created. You can observe an existing
point as a benchmark, in which case you will have the option of updating
only the elevation of the existing point, and its horizontal coordinate will
remain unchanged.
4. After some number of turning points and benchmarks stored, you will reach
the end of your level loop. You will close the loop by collecting a foresight
observation to the closing CBM. This can be either your starting point, or it
can be another point of known elevation.
In practice, the sequence of observations will be as follows:
Opening &
closing CBM
TP1
BM1
BM2
TP2
TP3
TP4
TP5
TP6
TP7
BM3
FS
BS
FS
BS
FS
BS
FS
BS
FS
BS
FS
BS
FS
BS
FS
BS
FS
BS
FS
BS
FS
BS