Dylan Beaudette wrote: > > There is a USGS technical report from the mid-1980s that's the standard on > > projections. While it is becoming more rare to locatate, see if you can find > > a copy. > > I think that Rich is referring to this USGS document, #1395 > > http://pubs.er.usgs.gov/usgspubs/pp/pp1395 > > Definitely worth the price if you want to become an expert in map projections.
According to that page, it's no longer available in hardcopy; however, you can download it as a PDF. > > Interesting. NH is a tall, narrow state so one would assume it would be > > within a single zone. Regardless, yes there is a way to reproject locations > > in one zone on the other, but it's non trivial and I've not done it. > > I wouldn't recommend it. The desirable properties of the UTM system > (i.e. the fairly good compromise between distortion, preservation of > angles, and preservation of area) only occur within a zone's > boundaries. The farther you move from the central meridian of the UTM > zone, the more distortion you will encounter-- therefore 'projecting' > UTM z10 data into UTM z11 is technically possible, but not a great > idea. That doesn't stop Norway doing it ;) http://upload.wikimedia.org/wikipedia/commons/e/ed/Utm-zones.jpg See 32V and 31X/33X/35X/37X. The SW fragment of NH which is in zone 18 is only around half a degree; projecting that into zone 19 isn't really an issue. Or you could just use a custom transverse Mercator projection with the central meridian at e.g. 71d30'W. -- Glynn Clements <[email protected]> _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
