This command calculates point coordinates given the angle
and distance from two or three reference points. The Z coordinate
can also be calculated in addition to the X,Y. If you only need the
2D solution, then enter the instrument and rod heights as 0.0,
the zenith angle as 90 and the distance as the horizontal
distance. The reference points are specified by point number.
These reference points need to be stored in the current
coordinate (.CRD) file before running this command.
After entering
the reference point, there is a dialog to enter the horizontal
angle, zenith angle and slope distance. The horizontal angle is
the horizontal azimuth or angle right from the unknown point to
the reference point. In the example, the backsight azimuth is 0
(due north), but this is not a requirement since the backsight can
be any angle. The program calculates the coordinate by
averaging the distance-distance and angle-angle solutions.
Since there is redundant data, the final calculated coordinate
will differ slightly from the individual measurements. For
example, in a 3-point resection, there are two different
distance-distance solutions (between the first-second
point and between the second-third points). The
program reports the difference between the final
coordinate and the individual solutions as the residuals
which act as an indicator whether the data is good.
High residuals suggest a problem with the input data. In
the dialog that displays the final coordinates and
residuals, there is a button to store the coordinates to
the current coordinate (.CRD) file with a specified
point number.
In the first Resection
dialog box, you can choose to use two or three reference points.
In the second Resection dialog box, you assign the reference point.
Point: You must
enter the point number of your reference point. These reference
points need to be stored in the current coordinate file before you run
this command.
Inst. Height: You must enter the instrument height.
Target Height: You must enter the target height.
If you need only the 2D solution, then enter the instrument and target
heights as 0.0.
In the Manual Read dialog box, you must specify parameters for the calculation.
Horizontal Angle:
You must enter a horizontal angle from the resection to the reference
points. The horizontal angle is the horizontal azimuth, or angle
right, from the unknown point to the reference point.
Zenith Angle: You must enter a zenith angle. For a
2D solution, set the zenith angle to 90 degrees.
Slope Distance: You must enter a slope distance from the
reference points to the resection.
You
are prompted for additional reference points and parameters.
Pulldown Menu Location: COGO >
Locate at Intersect
Keyboard Command: cresection
Prerequisite: Two or three reference points
File Name: \lsp\cogoutil.arx