Exercise 4: Calculating a Whole Circle Bearing in The Astronomic Direction Calculator

In this exercise, you will use the Astronomic Direction Calculator to calculate a whole circle bearing from solar observations by the hour angle method.

To calculate the whole circle bearing, you can use either a single foresight or a multiple foresight. For this exercise, you will use a multiple foresight because it is the more commonly used solar observation method.

This exercise continues from Exercise 3: Creating Survey Data Using the Survey Command Window.

Calculate a whole circle bearing using the Astronomic Direction Calculator

Note:

This exercise uses Survey-4C.dwg with the modifications you made in the previous exercise.

1. Click Analyze tab Ground Data panel Survey drop-down Astronomic Direction Find.
2. In the Astronomic Direction Calculator dialog box, specify the following parameters:

   Calculation Type

   • Calculation Type: Sun Shot Calculation

   Observation Chainage Data

   • Chainage Point: 2
   • Backsight Point: 1
   • Chainage Latitude: 36.04
   • Chainage Longitude: -94.1008
   • UT1 Time: 13.34024

   Ephemeris Data

   • GHA 00 Hours: 180.13402
   • GHA 24 Hours: 180.10431
   • Declination 00 Hours: 22.54505
   • Declination 24 Hours: 22.59437
   • Sun Semi-diameter: 0.15468
3. Click .

   A new observation set named Set:1 is displayed in the table.

4. Specify the following parameters for Set:1:

   Direct

   • Backsight Observation: 0.00
   • Sun Observation: 351.0835
   • Stop Time: 0.121590

   Reverse

   • Backsight Observation: 180.0005
   • Sun Observation: 171.3520
   • Stop Time: 0.154210
   Note:

   The observations will determine the true astronomic direction from the chainage point to the backsight point. Notice that after you enter the stop time for an observation, the observed and average direction are calculated automatically.

5. Click

   A new observation set named Set:2 is displayed in the table.

6. Specify the following parameters for Set:2:

   Direct

   • Backsight Observation: 0.00
   • Sun Observation: 351.1300
   • Stop Time: 0.12491

   Reverse

   • Backsight Observation: 180.0005
   • Sun Observation: 171.3800
   • Stop Time: 0.16030
7. Click .

   A new observation set named Set:3 is displayed in the table.

8. Specify the following parameters for Set:3:

   Direct

   • Backsight Observation: 0.00
   • Sun Observation: 351.1450
   • Stop Time: 0.13112

   Reverse

   • Backsight Observation: 180.0005
   • Sun Observation: 171.4145
   • Stop Time: 0.16313

   After you have entered the above data, notice that the Mean Direction value calculated by the Astronomic Direction Calculator is SOUTH87.967088EAST (if the drawing settings Direction Measurement Type is set to Quadrant Bearings).

9. Close the Astronomic Direction Calculator.

To continue this tutorial, go to Exercise 5: Creating Figures from Plots.