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