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 [email protected] [email protected] On Tue, Mar 10, 2009 at 7:55 PM, Kelly Jones <[email protected]> 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? _______________________________________________ newbies mailing list [email protected] http://lists.openstreetmap.org/listinfo/newbies
