math

[+sinemora]

If I have a known point, then have a direction in degrees minus declination and a distance, how do I find the grid or new coord's? I think there is a formula but I can't recall it. Any help would help. -SineMora-

[Swagger]

I think you're looking for the "great circle" formula. There's another (supposedly easier?) way to do it, but I can't recall the name right now.

 

--

Pehmva!

 

Random quote:

[+ZoomZoom]

Try Ed Williams web site. I'm sure this will answer your question.

 

"Every cache has it's rightful place."

[+fizzymagic]

quote:

---

Originally posted by -SineMora-:

If I have a known point, then have a direction in degrees minus declination and a distance, how do I find the grid or new coord's? I think there is a formula but I can't recall it.

---

 

The answer depends on a lot of things. Do you want an accurate result, or are you willing to approximate the Earth as a sphere? For magnetic headings of relatively short distances (less than 1 km or so) then the spherical approximation is probably OK, and there is a formula, which you can find at the Aviation Formulary.

 

For accurate calculations using the ellipsoidal model of the Earth, there is no closed-form equation. The calculations are done iteratively. You can try my program GeoCalc, which does those calculations.

[+apersson850]

Since the probability that you do have access to a GPS unit is high, considering that you are writing in this forum, you have an excellent tool there.

The GPS can be used as a calculation device too, for solving problems like this.

Enter the coordinates of the known point as a waypoint. Then project a new waypoint in the desired direction, at the distance in question, and it will calculate the new position for you.

 

Anders

[cvcaelen]

quote:

---

Enter the coordinates of the known point as a waypoint. Then project a new waypoint in the desired direction, at the distance in question, and it will calculate the new position for you.

---

 

I don't know 'bout other GPSr's,

but

the SporTrack does that: go to the position screen,

then menu

next choose "projection"

fill in the distance and degrees (angle)

and the answer comes as a projected waypoint.

[jarja_grl and G-man]

um yeah...I thought I was reasonably intelligent until I read this thread.

 

I was wrong.

 

Life is 10% what happens to you and 90% how you react to it.

[+Team Og Rof A Klaw]

assuming "declination" means magnetic declination and "direction in degrees minus declination" means true bearing...

 

delta x = r cos theta

delta y = r sin theta

 

latitude scales constantly to distance

 

longitude scales to distance as the cosine of latitude

 

hth

 

____________________________

- Team Og Rof A Klaw

All who wander are not lost.