Sun shots are entered in the Traverse View by highlighting a point for which the azimuth is to be computed, then choosing Tools | Sun Shot. Computations are based on the Local Hour Angle (LHA) method
The sun shot data is held in two dialogs.
The Sun Shot dialog box holds the occupied point information, the data from the Ephemeris, and the computed azimuth. Each sun shot will have its own data based on the location and time of the shot.
When you create a new sun shot, this data is copied from the last sun shot you took. If you exit the program and then return, you must re-enter all of the information in this dialog box.
The Tolerance value is stored in the registry and does not need to be re-entered.
The record dialog box is used to enter the shots and corresponding time.
You can enter up to 5 direct and 5 reverse measurements. When the bearing/azimuth is computed, the program will reject any measurements that are not close enough to the mean and will also insure that there are an equal number of direct and reverse readings.
The horizontal angles must be to the trailing edge of the sun.
To see which foresights are being computed based on a sun shot azimuth/bearing, choose View | Display Raw Data. Make sure the azimuth or bearing field is included in the display sequence. You will see the sun shot azimuths/bearings in the azimuth/bearing column.
When you record a sun shot measurement, you are recording local time based on the current setting of your hardware’s clock or watch. This time is not always accurate. The amount of error needs to be accounted for when computing the sun shot azimuth.
The Watch Correction +/- field in the Sun Shot dialog allows you to correct the recorded time to GMT before or after you take the shots. It does not affect the recorded time, it only affects the GMT computed from the recorded time for each measurement. You can have only one watch correction for each sun shot.
If you take a sun shot, without first synchronizing your time source, you can synchronize it when you come in from the field and use the updated correction to compute a more accurate azimuth.
In the Sun Shot dialog, the azimuth/bearing is computed automatically as you edit or enter the sun shot data. The computations are based on the equations given in “1996 Celestial Observations Handbook and Ephemeris” by Elgin, Knowles and Senne, Copyright 1995 by Elgin, Knowles and Senne, Inc.
An azimuth/bearing and corresponding error is computed for each measurement. The mean for the direct readings is computed separately from the mean of the reverse readings when determining which measurements to discard. Once this is determined, the azimuths from the remaining direct and reverse measurements are meaned to compute the avg. azimuth.
Any azimuth which differs from the mean (direct or reverse) by more than the Tolerance specified in the Sun Shot dialog is discarded. If there are an unequal number of direct and reverse measurements after discarding some, the measurements with the most error are discarded until there are an equal number of direct and reverse measurements.
The Theta Factor specified in the Sun Shot dialog is added to the average azimuth/bearing to arrive at the sun shot azimuth/bearing displayed in the Sun Shot dialog.
Sun Shot dialog
Sun Shot Observations dialog
Premium, Professional