Data Base Distance from Point

Accessed from the Edit button Field geometry on the database table display window.

• If the data base does not already have a "DIST_KM" field, it will be added.
• You set the latitude, and longitude of a point, and the program will compute the distance (in km) from each point in the data base to that point.
• To pick graphically, right click on the point, add its coordinates to the clipboard, before selecting the option, and then you can paste the coordinates into the location request.

Distance algorithm comparison (also on the Edit button Field geometry) does the Vicenty (the default, more accurate, and the only one recommended), plus haversine, and cosine distance formulas (not recommended)

• Haversine formula assumes spherical earth, and has errors over very small distances
• Cosine formula assumes spherical earth, and has errors over very long distances (opposite side of the earth)

Other ways to measure distance.

Last revision 5/8/2019