This routine calculates true north and/or grid north bearings by solar observation. It uses the Local Hour Angle method. The routine calculates Ephemeris data, thus alleviating the necessity of obtaining a Solar Ephemeris. The True North option calculates the true north bearing to mark. This option requires no zone/ellipsoid information. The True North & Grid North option calculates both true north and grid north bearings to north. The convergency angle is also shown.
Calculate true north, or true north and grid bearing (<True
north>/Grid Bearing: type T,
press Enter
Choose field method (Leading edge/Trailing edge/<Center>): choose method, press Enter
If a Roelofs prism is being used, the Center Method should be
selected. If not, select one of the other options. The Trailing Edge
Method is the more popular of the two remaining methods.
Date of observation as MM/DD/YY or MM-DD-YYYY: For example
04/08/03.
Enter latitude of instrument point as DD.MMSS: For example 36.0545
Enter longitude of instrument point as DD.MMSS:
The following input loop will begin:
Obs. #1 - Time of observation as HH.MMSS: For example 15.3030
Enter angle to mark as DD.MMSS: Angle in the instrument when
backsighting the mark.
Enter angle to sun as DD.MMSS: Clockwise angle from mark to sun.
The angle to the mark always has a default value of the last entered
Angle to Mark. Each observation is numbered and the true bearing to the
mark will be calculated. There is not limit as to the number of
observations that can be made from a setup. After data entry is
complete, press Enter.
The following options appear:
Edit/<OK>/Quit: If
you choose Edit, you will have the
following options:
ADD/Change/Delete/eXit:
Add: Allows for
addition observation data entry.
Change: Allows editing of
existing data. When selected a prompt for
Enter observation to change will be displayed. Choose which observation
number to edit. You will then be prompted with the initial input
prompts for the observation again. The original input values will be
the default values for each prompt. To change the value, simply enter
new data.
Once Delete: This will
delete the specified observation data. Choose the
observation number to delete.
eXit: This exits the change
routine.
OK: The bearings from all
the observations will be averaged and shown
as well as the True Bearing. For example: No. Time Angle-@-Mark
Angle-to-Sun True-Brg-to-Mark.
1 12.3030 0°00'00" 20°00'00" N
73°05'43"E
2 12.4456 0°00'00" 21°00'00" N 74°17'15"E
Average True Bearing: N 73°41'29"E
Calculate true north, or true north
and grid bearing (<True
north>/Grid Bearing: G
The following dialog will be displayed. Select the state in which the
observations were made. All fifty states are available, as well as PR
for Puerto
Rico and UM for Universal Transverse Mercator. If the state is divided
into zones, you will be prompted for the
zone you are working in.
Enter zone (N,S): Enter the
zone. After entering the zone, if applicable, the input loop described
for
True North calculation as detailed above will begin. After data entry
the same options, Edit/<OK>/Quit as detailed
above will be displayed. Pressing OK averages and displays the bearings
from all the observations taken along with the Average True Bearing,
Average Grid
Bearing and the Convergency Angle as follows:
No. Time Angle-@-Mark Angle-to-Sun
True-Brg-to-Mark
1 12.2222 0°00'00" 20°00'00" N
72°57'31"E
2 12.4444 0°00'00" 22°00'00" N
74°20'51"E
Average True Bearing: N 73°39'11"E
Average Grid Bearing: N 72°15'12"E
Convergency Angle: 1°23'59"
Pulldown Menu Location: COGO
Keyboard Command: solarobs
Prerequisite: None
File Name: \lsp\sideshot.lsp