Using Geocap you can easily calculate the shortest distance between two points following the earth's curvature. This is done with the calculate earth distance dialog. The dialog is opened from the main menu under Geodesy. Select Calculate earth distance and the dialog will appear. Select the datum and coordinate system of the data in the display window. You can also select which unit you want for distances. Default unit is in meters. You can also select which distance calculation method you want to use. Flat earth calculates the distance between the two points as a straight line. Flat earth will automatically use Earth centered sphere if the selected coordinate system is geodetic. Earth centered sphere approximates the earth as a sphere with a constant radius. Radius adapted sphere approximates the earth as a sphere, but uses the radius of a sphere with the same curvature as the ellipsoid used by the selected datum, at the midpoint between two points. Ellipse approximation calculates the distance along the ellipsoid using an approximation algorithm. The dialog will calculate the latitude and the longitude of the last selected point. It will also calculate the distance between the last two selected points. A point is selected by clicking in the display window in 2D mode. In 3D mode you can use the y key on the keyboard to select points on a surface. The distance calculations will not use the z value (that is the height value) in its calculations. |