In the Astronomic Direction Calculator you can select Sun Shot or Star shot to calculate astronomic directions.
Sun shots calculate a direction using solar observations by the hour angle method and use a multiple foresight method. Star Shots calculate a direction from Polaris or a star observation by the hour angle method and use a single foresight method.
To calculate an astronomic direction using the Sun Shot or Star Shot calculations
- Click Analyze tab
Ground Data panelSurvey drop-downAstronomic Direction
.At the Command prompt, enter SurveyCalculator. - In the Calculation Type list, select either Sun Shot Calculation, or Star Shot Calculation.
- Under Observation Station Data, specify the following:
- Station Point
- Backsight Point
- Station Latitude
- Station Longitude
- UT1 Time (Sun Shots only)
- Under Ephemeris Data, enter the following:
- GHA 00 Hours
- GHA 24 Hours
- Declination 00 Hours
- Declination 24 Hours
- Sun Semi-diameter (Sun Shots only)
NoteEnter zero (0) if you are sighting either the center or both the trailing and leading edges of the sun. The left edge is always the leading edge at latitudes greater than 23.5 degrees north and greater than 23.5 degrees south. If only the left edge is being sighted (left when facing the sun), then the semi- diameter is positive; likewise, the semi-diameter is negative when only the right edge is sighted.
- Click
to create an observation set. Enter Direct and Reverse observations for the Backsight Observation, Sun Observation or Star Observation and the Stop Time. The observations determine the true astronomic direction from the first setup to the backsight. When you enter the stop time for an observation, the observed and average directions are calculated automatically.