Geodetics Calculator

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The Geodetics Calculator is designed to solve the first ("direct") and second ("inverse") geodetic problems with an accuracy of 1e-6 meters over a range of 27 different reference ellipsoids and spheriods.

Background:

The first ("direct") geodetic problem is defined in the following manner: given a point (in terms of latitude and longitude) and a direction ("azimuth") and distance from that point to a second point, determine the location (in terms of latitude and longitude) of the second point.

The second ("inverse") problem is defined in the following manner: given two points (in terms of latitude and longitude), determine the direction ("azimuth") and length of a line (in our case, both a geodesic curve (a great circle) and a rhumb line) that connects them.

Usage:

*To solve the first ("direct") geodetic problem, simply enter the origin point, fill direction and azimuth fields and press the Calculate button.

*To solve the second ("inverse") geodetic problem, simply enter the origin and destination points and press the Calculate button.

*In order to change the units in which the input or output fields are given, simply choose a different measurment unit and press the Calculate button.

Terminology:

*Geoid Altitude output field rtepresents the height of the local geoid (EGM96 = Earth Gravity Model 1996) above mean sea level at the origin and destination.

*Forward output field represents the azimuth from origin point to destination point.

*Backward output field represents the azimuth from destination point to origin point.

*Direct output field represents the length of a straight line ("geodesic curve" / "great circle") connecting the origin and destination point, along the reference ellipsoid.

*Rhumb output field represents the length of a rhumb line connecting the origin point to the destination point, along the "meridional earth spheroid model" (radius of 6367.445[km]).

*Latitude and Longitude output fields represent the location of the point located at a given azimuth and distance from the origin point (they are given in degrees with a decimal notation).

Notes:

*Origin and Destination points location can be entered in two different notations:

> degrees decimal notation: choosing "decimal" would require the location input field to be entered in degrees in decimal notation, eg.: 32.156845 or -4.563542.

> degrees/minutes/seconds notation: choosing "d/m/s" would require the location input field to be entered in degrees/minutes/seconds notation, eg.: 32 50 6 or -14 29 50. notice that a space should be enter between the degrees, minutes and seconds.

*Longitude is given in the boundary of [-180.0, 180.0] degrees. Negative longitude represents the western hemisphere and positive longitude represents the eastern hemisphere.

*Latitude is given in the boundary of [-90.0, 90.0] degrees. Negative latitude represents the southern hemisphere and positive latitude represents the northern hemisphere.

*If the origin and destination points are the same, than the distance between them would be zero, and the azimuth between them would be NaN ("not a number").

*If the distance entered by the user is such that the reference ellipsoid would be encircled, than the calculator would take it into consideration.

*Output fields are labeled using indent font, to seperate them from input fiields.

*Geoid altitude is calculated using a bilinear interpolation performed upon a 0.25 degrees grid of point value in a "tide-free" system. The Geoid is given relative ot the WGS84 ellipsoid. Maximum error in Geoid altitude is one meter.

*Rhumb line distance is calculated using earth spheroid radius of 6367435[km]. Deviation from other calculators might originate from the usage of a different earth radius.

Questions or bug reports? please contact me at malta.dan@gmail.com.

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