On Wed, Mar 11, 2009 at 8:09 AM, Matt Maxon <[email protected]> wrote: > Kelly Jones wrote: > As others have said... No the GPS isn't a suitable surveying instrument > The Pocket Transit > http://en.wikipedia.org/wiki/Brunton_compass
yes. having tried the Lensatic infantry map reader's compass, I have one of these mapmaker's/surveyors pocket units on order for this sort of purpose, whether useful to OSM or not. > This is one inexpensive relatively. good ones cost about the same as good GPS. http://www.thecompassstore.com/pockettransit.html cheap plastic ones without extended base peep (thus less accurate) are cheap like cheap gps http://www.thecompassstore.com/cadet.html military surplus if in good condition are the best buy. > and used properly accurate device yes US army WW2 training&field manuals for map-reading have some info but more is in artillery reconnaissance and field mapping manuals, where calibration and use of the military model for actual surveying is discussed. > It can be mounted on a tripod which IMO is essential for this type of > surveying note you need a non-magnetic tripod to avoid disrupting the compass. not sure if the exclusion of magnetic lines in Aluminum is strong enough effect to be a problem or not. For approximate work, one can avoid trig with the Brunton 6050M Pocket Transit or US M2 Artillery Compass (same unit, some manufactured by Brunton, some by others in wartime) which is calibrated in Mils (meter deflection at kilometer range) but it will run 2% over in the range where sin x = x approx holds. But one can still use Mils trig when needed. It feels good to finally understand why Mils are the natural metric angular measure. -- Bill [email protected] [email protected] _______________________________________________ newbies mailing list [email protected] http://lists.openstreetmap.org/listinfo/newbies
