Projecting Waypoints

[+consciousNOT]

If a person had two waypoints and wanted to use the first as a starting point and project to the second, how can this be calculated? It would seem to me that it would have to be calculated, not estimated or the error would be too large over a long distance.

Thanks.

[+Blaidd-Drwg]

I would bet theres an easier way, but off the top of my head, I'll give you this opiton. Assuming your doing this at a location where you have access to a computer, type both locations into EasyGPS, set one of the points as a home point and it will calculate the distance and direction to the second point. I tried this and depending on how close the points are, the answer will be in either feet/meters, or in mile/km to the nearest 1/10th. Direction will be displayed to the 1/10 of a degree. Just one of many methods, I'm sure. Of course that being said, if you're going over a long distance, even a 0.1 measurement error could be a lot. For instance, it you project over a distance of 10km or about 6.2 miles, the azimuth error of 0.1 would amount to about 17 meters or 55 foot. Longer distance would increase at about the same rate. Basically, a 0.1 degree error is going to throw you off by about 1.7 meters per km of range, or 8.3 foot per mile of range Edited July 11, 2004 by Team Madog

[+sbell111]

Assuming this is for local coords, the lazy man's way is to put both coords in your GPSr. Go to the first coord and hit GOTO for the second. The smart little guys who live in the GPSr will tell you how far and in which direction.

[+LordSaw]

The calculations you need to project a new waypoint from a known waypoint based on distance and bearing involve transformation of spherical coordinates and a lot of trigonometry. BUT there is hope, I googled this and found a Calculator for Distances between Geographical Locations Fill in the form on the right. Don't know how accurate it is, but it should be close.

 

Cache Well

[+rickrich]

You can find a modified version of Gazza's Geodetics calculator, which knows how to deal with MinDec format, here: http://mngca.rkkda.com/geodetics.html

[+Mr Smiles]

Sitting in my easy chair, wanting to know the distance between a point X and a point Y, and both are somewhere else in the world, I use the routes feature on the GPSr which tells me the leg distance. So far, I have not found this to be flawed. Are there situations where this would not be reliable?

[Tahosa and Sons]

If a person had two waypoints and wanted to use the first as a starting point and project to the second, how can this be calculated?

Simple just go to a waypoint on a Garmin and do the projection thing.

[+EScout]

If you have 2 known waypoints, do as Thicketfella says, create a route in your GPSr with these 2 points and it will give the bearing from the first to the second and the distance.

 

With an actual projection, you know the coords of one waypoint, and the distance and bearing to the second. Use the projection feature on your GPSr and it will give you the coords to the second waypoint.

Edited July 11, 2004 by EScout

[+consciousNOT]

I think I count 4 methods(5 if you count the second mathematical formula) given by my fellow goecachers. I will try them all, see what happens and post it here. Don't expect an answer soon , though, I am still contemplating this cache--Thanks!

[+AtoZ]

If your still interested email me and I'll help you out. Bassically it is cartesina to polar coordinate conversion and vis versa.

cheers