gifGEODYSSEUS

OpenGL interactive map projection and navigation for MS® Windows and Linux. Map projections and traverses may be saved as PostScript files.

The program was written in response to an academic moderator trolling me with the question "What is a geodesic line? Please let us know if there is anything else we can help you with." The program allows sophisticated calculation of direct and inverse traverses over both the globe (using a specified reference ellipsoid), and various 2D map projections. The traverse method itself can be changed via the Log window, offering Vincenty, Rudoe, Rainsford, Helmert. Other options are available if you examine the source code (Eg Thomas), though most of these have now been incorporated into the Boost C++ library, without my consent or even so much as a polite email. The source code is available via the Sourceforge server.

0.1.2b Screenshot   0.1.5a Screenshot 1    0.1.5a Screenshot 2   0.1.5a Screenshot 3   Leg Computer

As well as plotting the geodesic between two specified points (obtained via lat/long entry or name database lookup), the program also plots the loxodrome which can be divided into any number of 'Legs' which subdivide the geodesic. The Leg Computer allows the user to compute airspeed, windspeed, track (groundspeed) and drift for each leg. The legs, with all respective navigational details, are printed in the Log window when the traverse is re-calculated. (A traverse is re-calculaetd by clicking its gear button in the Traverse Tree).

The program features a highly detailed world vector map which was traced over the NASA Visible Earth Blue Marble images http://visibleearth.nasa.gov. The lines for the land masses were drawn in Adobe Illustrator over a Mercator projection of the Land Shallow Topo data set at 13000x13000 pixles. The image was split into four quadrants: NE, NW, SE, SW. The map is drawn using straight line segments for rendering in OpenGL. The intention is to make it accurate whilst keeping the vertex count to a minimum.

A screenshot of part of the NW quadrant (reduced by 50 %) is here. Another screenshot of the SE quadrant, (enlarged by 200 %) is here.

The Antarctic continent was generated from both the Blue Marble data and from a Polar Stereographic projection by the Australian Antarctic Data Center which was downloaded from Google images. An inverse Stereographic projection with true scale at 71° South was performed back to the reference ellipsoid; this generated vertices for both land and sea ice.

To verify the accuracy of the projection, the map generated by Geodysseus was superimposed on the one generated by Australian Antarctic Data Center. You can view this here. The sea ice is drawn with dashed lines.

Download

The latest release can be found on the Geodysseus Download page.

Documentation

Documentation is included with the program.

© 2018 Nicholas Shea