[OSM-newbies] Triangulation using GPS w/ magnetic compass

[Bill Ricker]

Kelly,

that's how professional surveying has done Mountains for 250+ years,
and the reverse of how they did their triangle chains and benchmarks.
I would love to find something for which that technique would be
applicable to for OSM because I think it is retro cool.

You need very accurate angles and merely accurate positions to get
merely accurate positions, which is why professional transits have
expensive precision alidades still and have Differential GPS
receivers.

If you can measure angles very precisely, it works better for tall
pointy things like towers, steeples, mountains better than flat
foreshortened streets.

The after processing of a traditional triangle chain has a lot of work
to do, somewhat less since you're taking the GPS posits at each point,
but laborious none the less.

anywhere you  CAN drive walk or ride will be quicker to trace.

Anything you can't walk to is probably old enough to be traceable on
yahoo imagery. If it's new and not walkable, the paranoids may get
excited if they see you triangulating it!

But i really would like to triangulate something too.

-- 
Bill
n1vux at arrl.net bill.n1vux at gmail.com



On Tue, Mar 10, 2009 at 7:55 PM, Kelly Jones
<kelly.terry.jones at gmail.com> wrote:
> If you have a GPS device w/ an accurate magnetic compass, you could
> record the directions/angles to several far-away points from one
> location, then move to another position, and record the new
> directions/angles.
>
> For each point, you know two angles and the length of the side between
> them (ie, the distance between your two positions), and can use
> triangulation to determine their points' latitude/longitude.
>
> This would be a great way to map hard-to-reach locations.
>
> People with panaromic city views could map dozens of streets in just a
> few minutes.
>
> Has anyone tried this approach?