Lab V Section I: Forward and Inverse Conversions

Section I: Forward Conversions

The Geographic Calculator can perform Forward geodetic conversions. This function allows the user to calculate a coordinate by its distance and heading (Azimuth) from a source coordinate using either Geodetic or Rhumb Line methods (Set in General Preferences).

For example, the user has a coordinate (x, y) that is specified in Geodetic Lat/Long in WGS84 and would like to calculate the coordinate that is 7 degrees (azimuth), 100 meters away.

Objective: To calculate a new coordinate that is a specified direction and distance away from a source coordinate.

Follow these steps to complete a forward coordinate conversion:

  1. Open the Geographic Calculator and click the Interactive Conversions tab.

  2. Determine which half of the interface will be used as the Input area. For this exercise, the left side will be the Input side.

  3. Enter this Geodetic Lat/Long coordinate:

Name: Point A

Latitude: N 44 13 36.96

Longitude: W 69 46 08.11

  1. Enter the Input Coordinate System:

Group: Geodetic Latitude/Longitude

System: Latitude/Longitude

Datum: WGS84

Note:

When performing Forward conversions, the Input and Output Coordinate Systems must be based on the same reference ellipsoid. In this example, the coordinate system will not be converted.

  1. Select the same coordinate system for the Output area:

Group: Geodetic Latitude/Longitude

System: Latitude/Longitude

Datum: WGS84

  1. To change the display of the units, click the Format button. Specify the Output Format as DD MM SS. Also, set the Display precision (decimal places) to 2 and select the N/S or E/W as prefix control button. The click OK.

  2. Click on the (Forward) control button.

The dialogue box that appears prompts for three parameters:

Geodetic/Grid: Specifies the type of conversion that is being performed. This setting will be set to match the selected coordinate systems.

Distance: Refers to the distance between the source coordinate and destination coordinate. The linear unit type may be changed to suit the project.

Azimuth: Refers to the angle applied to the forward conversion:

Enter the following values and appropriate units:

Radio button: Geodetic

Distance: 1000 meters

Azimuth: 007 degrees

Make sure you specify the units using the appropriate units button.

  1. Click OK.

The coordinate 1000 meters, azimuth 007 degrees from the source coordinate is:

N 44 14 09.12

W 69 46 02.62

This information will be displayed in the output half of the Interactive Conversions screen.