>My first attempt at a distance calculation (using a floating

point

>implementation of the haversine formula) required 5 trigonometric

function

>calls, two square roots, and several floating point

divisions.

>Something's still not quite right - two points with the same

coordinates

>show a distance of 323 feet. Gotta track that one

down. But it seems to be

>good enough for distances in miles -

everything seems to be within about 10%

>of what it should be.

Have you had a look at the distance
calculation routines we used on the HamHUD? We were very limited in the math
functions on the PIC used it that device, yet Steve still managed to get pretty
accurate distance calculations. The same type of fudge factor concept was talked
about quite extensively when we were trying to get it all hashed
out. >Now for bearing calculation. Anyone know how

to fake an arctangent

>calculation?

I wrote a C routine to convert lat/long positions
into the 16 compass rose directions that is used in the HamHUD. Are you looking
to calculate it out to integer degrees, or general compass directions. Using
simple math and comparisons gave us a pretty decent bearing
routine.

James

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