Nav library

[mjcoon]

Originally Posted by derez

I shall try to work on the fortran version, it is more understandable to me.
It will take time.

Thanks David. I've been looking at the various versions too. It does seem rather complex, and I don't think that any of the calculations other than declination/variation would be of interest...

Mike.

[derez]

Version 1.3 includes MagneticData class, provides magnetic declination (variation), Inclination and Grid-Variation for point defined by its coordinates.

It is based on an algorithm found here World Magnetic Model - Software Download
thanks to mjcoon !
Please read the notes there about the accuracies. Remember that the algorithm does not consider local effects of the materials in the ground, and this may cause a much larger difference than the accuracy.

The results are quite close to what this site computes: http://www.magnetic-declination.com/

The data file is valid until 2015.

[mjcoon]

Originally Posted by derez

Version 1.3 includes MagneticData class, provides magnetic declination (variation), Inclination and Grid-Variation for point defined by its coordinates.
...
The results are quite close to what this site computes: Magnetic Declination

Terrific, thanks David. I confirm that I get the same value for declination for my location as I get from the various versions at or downloaded from the NOAA web site.

I guess since the data needs to be refreshed ever five years (!) it is better to keep it separate rather than incorporating it inside the DLL as a resource.

Now I can (for the moment) stop trying to dredge up what I used to know about C++ and try incorporating what you have done into (my version of) GPS4PPC.

BTW although your latest nav.chm does include the new magnetic value methods, the overview section misses out mention of version 1.3.

Mike.

[derez]

Thanks for the reminder, corrected.

[derez]

I corrected a bug in the MagneticData, ver 1.31

[mjcoon]

Hi David, I've spotted an ommission from the suite of test code that you included: trying to load Geo_Mapcal2.sbp (just to see what it does!) I get a message that module mAbout.bas is missing. No doubt it isn't crucial unless you click the "About" menu item...

Mike.

[derez]

Thank you, I replaced the program with a new one which use about.dll instead of the module (included).