UAV Guidance

josefvs

I am trying to find a working algorithm to convert LAT/LONG to UTM, much the same as in a Garmin GPS. This so my autopilot can calculate it’s waypoints internally and not use the GPS itself.
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Can anybody help?
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Thanks, Yossi

John Abshier

Here is a link to Java code and also has links to information

http://www.ibm.com/developerworks/java/library/j-coordconvert/

CCraig

Yossi,

The formulas are really long. I even bought a few um-FPUs to try to put it all in there. I won't say I gave up, but I have put that project on the back burner. I think it will take a lot of work. I'd like to see what you come up with. It was beyond me.

Here's another link:

www.uwgb.edu/dutchs/UsefulData/UTMFormulas.HTM

HTH, Chris

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John Abshier

Instead of going all the way to UTM. There are formulas that take two lat/long points and give the distance and direction from one to the other. I was able to find some AWK code.

# input is lat1 long1 lat2 long2
# lat1 is [noparse][[/noparse]NS] deg min sec if using deg and min sec must = 0
# likewise if only deg then min and sec = 0
# long1 is [noparse][[/noparse]EW] deg min sec
# the 2's are like the 1's
# 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
# Example: N 53 09 02 W 01 50.75 0 N 52 12 19 W 0.25 0 0
# if the [noparse][[/noparse]NS] or [noparse][[/noparse]EW] don't match returns an error
BEGIN { r = 6371
kmToFeet = 3280.839895
degToRadians = 3.14159/180.0 }
{if ($1 != $9) {print "Error in lat ", $0 ; next}}
{if ($5 != $13) { print "Error in long ", $0; next}}
{lat1 = $2 + $3/60.0 + $4/3600.0
lat2 = $10 + $11/60.0 + $12/3600.0
long1 = $6 + $7/60.0 + $8/3600.0
long2 = $14 + $15/60.0 + $16/3600.0
deltaLat = lat2 - lat1
deltaLong = long2 - long1
deltaLat = deltaLat * degToRadians
deltaLong = deltaLong * degToRadians
lat1 = lat1 * degToRadians
lat2 = lat2 * degToRadians
a = sin(deltaLat/2)^2 + cos(lat1) * cos(lat2) * sin(deltaLong/2)^2
print a
dx = 2.0 * r * atan2(sqrt(a), sqrt(1-a))
bearing = atan2((-sin(deltaLong)*cos(lat2)), (cos(lat1) * sin(lat2) - sin(lat1) * cos(lat2) * cos(deltaLong)))
print $0
print "distance = ", dx, "bearing = ", bearing/degToRadians }

W9GFO

It's been a while since I looked at my code but what I did was take the difference between the target lat/long and current lat/long to give me an X/Y position and then perform a couple of trig calculations to give me distance and bearing.

CCraig

W9GFO,

Any chance to did up your formulas? Don't need the whole code just the trig. If you can find it. No big deal if not.

Thanks, Chris KE6GS

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I'm not scared of your robot. I'm covered by Old Glory (youtube)

W9GFO

CCraig said...
W9GFO,

Any chance to did up your formulas? Don't need the whole code just the trig. If you can find it. No big deal if not.

Here is my solution;

dir = distE ATN distN

  IF dir < 64 THEN                             ' rotate so that 0 is north
  dir = dir - 64
  ELSE
  dir = dir + 192
  ENDIF

  dist = ((distE HYP distN)*workVal)

The difference in lat/long from where you are to where you want to be are stored in values distN and DistE

I'll attach the whole program so you can check it out further.

CCraig

Thank you very much, Chris

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
I'm not scared of your robot. I'm covered by Old Glory (youtube)