GreatCirc can calculate the Great Circle Distance between any two points on the earth. Also, given a starting point, direction and distance it can calculate the Great Circle End Point. In both cases, GreatCirc will plot the resulting Great Circle path on a world map.
GreatCirc can also do a Coverage Area calculation, given a centre point and a range, GreatCirc will plot the resulting circle on a world map and calculate the area of the earth's surface enclosed within the circle. New, in version 2.0, GreatCirc can also calculate and plot the Rhumb Line distance between two locations.
The "great circle path" is the shortest direct route between two points on the earth's surface. Because the earth is a globe, the shortest path between any two points lies on a circle which is centred at the earth's core and passes around the surface of the world. Such a path will appear to be a curved line when drawn on a flat world map beause of the distortion inherent in mapping the globe onto a flat map. See the Wikipedia article for further information on great circle distance.
GreatCirc will calculate both the common "Direct Problem" and the "Inverse Problem", as well as doing a separate "Coverage Area" calculation. For the Direct Problem, given a starting point and the initial bearing and distance it will calculate the latitude and longitude at the destination.
For the Inverse problem, it will calculate the distance and azimuth bearings between any two points, given the latitude and longitude. In both cases, GreatCirc will plot the resulting Great Circle path on a world map.
GreatCirc will also do a coverage area calculation, given a centre point and a range, it will plot the resulting circle on a world map and calculate the area of the earth's surface enclosed within the circle.
Great Circle calculations are based on spherical geometry, and can be relatively simple if the earth is assumed to be a perfect sphere. However, the earth is known to be in fact a flattened ellipsoid and not a sphere at all.
GreatCirc uses the standard WGS84 ellipsoid earth model commonly found on GPS receivers, to provide the most accurate calculations, however the option to do calculations using a spherical earth model is also available to allow comparisons between the two techniques. When it comes to the WGS84 ellipsoid calculations, this application relies on the Vincenty algorithm.
A batch mode is also available to allow calculation of multiple distances and waypoints along a path and plot them on the world map.
GreatCirc may be of interest to mapping professionals interested in finding true distances between locations on the earth's surface, or the general public interested in plotting their travels on a world map.
The basic calculator function can be downloaded and used free of charge. To access the extended batch mode, file exporting, and magnetic azimuth tools you will need to register.
Here are some key features of "GreatCirc":
- Saving map images or exporting to other programs
- Saving calculation results to reports or exporting to other programs
- Calculate Magnetic azimuths (compass directions)
- Batch Mode processing to process and plot multiple paths and waypoints
- Choose points from a user's own text file list
- View and zoom the map, in Mercator or Globe view, on the main window (batch mode is always flat map).
- Load alternate flat map images in batch mode.
- Screen resolution set to at least 1024x768.
- Basic Features (Free):
- New item in Tools menu allows locations to be entered in Australian Map Grid (AMG) coordinates.
- Converted Help system from WinHelp to HtmlHelp format to improve Windows 7 support.
- Improvements to context sensitive help & menu layouts.
- Advanced Features (requires Registration):
- User Site Selection tool now allows the user to pick sites from GPX and AMG format files, as well as default maplist TXT files. And now also ignores sites from the input file which have no name label.
- Batch Mode will now allow users to load and plot GPX format (GPS eXchange Format) files used by common GPS software. Waypoints will be labelled, and Routes and Tracks will be shown as connected lines.
- In Batch Mode, when opening a new input file, the user is now given the option whether to replace existing data, or append the new data to the existing plot.
- In Batch Mode, users can now save the map plot data to a simple maplist TXT file. eg. when two i...