GPS & Coordinates & distance?

[azdesertrhino]

I did a search on the 'net and on this forum but really didn't come up with anything on this issue. Suppose I have a given coordinate on a GPS. Now I want to be 900 feet east of that coordinate and 800 feet north of it. Is there a mathematical formula to figure out what my GPS reading should be for the new position I want to be in? I realize the distance between longitude lines is not constant so your position on the globe would be a factor, but say here in Arizona, is the a way to figure that out?

Thanks,

 

[Fergie]

What form are the coords in? UTM, 8 dig, 4 dig, degrees?

Fergie

 

[azdesertrhino]

Degrees, min, sec. The actual coordinates are of a spot in the middle of nowhere in the northern arizona desert. Then the actual spot to be located is given in measurements from those coordinates.So many feet east, then so many feet north.

Thanks,

 

[Fergie]

Well, the only way I know of is to get a map of the area, and plot the points as that is the way I was taught.

I don't know GPS systems that well, so that is my best advice.

Find a map of the area. Plot your point, and then plot the second point, and enter it in your GPS.

Fergie

 

[Grifter144]

fergie got it right, i always take a map...what happens if your GPS dies? resort to what...in the army we always carry a back up map and when moving from location to location you must plot out the point on the map before you enter it in your garmin....if you really wanna test yerself...put away the garmin and do it with a compass....oh and word of advice the rest of the world( on a grander scale) uses clicks(1 click = 1000 meters), ie most maps that are graphed out in squares, each grid square = 1 click =1000 meters.... so try getting used to that scale..after that its easy to break down the square into more manage able increments... i would suggest going out in your local woods and plotting out a 1000 meter line and walkin/driving it just to get a feel for what 1000 meters feels like..Good luck man..
CPL Maier

 

[Fergie]

Yup yup...the Army is who taught me too. Never failed LandNav.

 

[azdesertrhino]

I carry maps, a compass and a GPS. I can use a map and compass. The question was more out of curiosity as to if it is mathematically possible to figure out the GPS coordinates given one set of coordinates and measurements to the other point. Appreciate the input. Also had to pass land navigation in the Army long before GPS was a tool to use. We didn't have a Garmin to make sure we were right, so you better know how to do it right.

 

[DrMoab]

I carry maps, a compass and a GPS. I can use a map and compass. The question was more out of curiosity as to if it is mathematically possible to figure out the GPS coordinates given one set of coordinates and measurements to the other point. Appreciate the input. Also had to pass land navigation in the Army long before GPS was a tool to use. We didn't have a Garmin to make sure we were right, so you better know how to do it right.

You might be able to figure this out if you used the UTM grid. With UTM everything is perfectly square but this isn't so with the degree,min,sec rule.
The reason is this....If you take a globe and look at the lat,lon lines as you if you start at the equator and work up toward the north pole you will see the lines get closer and closer together. Mathmaticly it would be pretty hard to calculate.

Clear as mud?

 

[Matthew Currie]

You might be able to figure this out if you used the UTM grid. With UTM everything is perfectly square but this isn't so with the degree,min,sec rule.
The reason is this....If you take a globe and look at the lat,lon lines as you if you start at the equator and work up toward the north pole you will see the lines get closer and closer together. Mathmaticly it would be pretty hard to calculate.

Clear as mud?

Disregarding irregular terrain, latitude is directly translated into distance, since the lines are parallel and evenly spaced. One degree of latitude equals 60 nautical miles wherever you are. Once you do that math, you then ought to be able to find out the distance between longitude lines at that specific latitude, and calculate from there. I think there are standard navigational references for this, but I wouldn't be surprised if they're too coarse to get the desired results in feet. You'd always need to get your latitude first, and I imagine it would be needlessly complicated compared to using a map, but it ought to be possible in theory.

 

[azdesertrhino]

In other words, as stated by someone else, "CLEAR AS MUD"!:wave:

 

[Boatwrench]

For AZ to your GPS coordinates: Southern hemisphere and east of Greenwich will be different.

Add 8 seconds N (go up in value numerically)

Subtract 9 seconds W (go down in value numerically)

Will put you in close proximity.

here's the equation I used.
A degree of Lat/Long is equal to 60 nautical miles (as previously stated).
1/60 of a degree or a minute = ~ 2,000yds or 6,000'
1/60 of a minute or a second = ~100 ft


have fun,
Tom

 

[karstic]

Here's a place to start

http://pollux.nss.nima.mil/calc/degree.html

 

[Captain Ron]

HO 229, Volume III, (30-45)

Interpolate from the 2 nearest lines of Longitude 1 second of arc apart, on either side of the position.

The Latitude is easy.

Just remember, it's "nautical miles"... 6069.55 feet...

--ron

 

[azdesertrhino]

Boatwrench, Captain Ron & Karstic,

Very cool, that's the kind of info I needed, just to see if I can do it. Thanks for your time & response. Thanks to everyone else that took the time to respond!!

TKX, :wave: aperwork