They are reasonable reasons, but traversing zones is a pain, you should see if using one or the other is sufficient. I would check carefully the distances you get against ellipsoidal calculations.
Cheers, Mike On Sat, 28 Mar 2015 07:30 Andrew Duff <[email protected]> wrote: > A number of field folks prefer UTM because > > -it matches legacy paper USGS quad map series traditionally used for field > navigation > -units are in meters and can be used to gauge field distances from a > coordinate readout > > > > > On Mar 27, 2015, at 10:48 AM, Michael Sumner <[email protected]> wrote: > > > > There is no good natural reason to use UTM, it mistifies me why our > > community tolerates this bizarre default. I always use a local equal-area > > projection unless some other compromise dictates a different choice. > > Cheers, Mike > > > > On Fri, 27 Mar 2015 21:28 Barry Rowlingson <[email protected] > > > > wrote: > > > >> If you have lat-long data that crosses two UTM zones then its > >> generally okay to just pick *one* and transform all the points to > >> that. Use the one that has the most points in. Basically use the UTM > >> zones as guidelines to pick one UTM zone coordinate system. Unless > >> your data spans several zones and you want quite high accuracy of > >> distance measurements. Some points bleeding over into an adjacent zone > >> are no problem. > >> > >> All projections are approximations to the earth's spheroid, so points > >> that are within a single UTM zone have some distortion in their > >> distance or angle relationships. Transforming points that are within > >> an adjacent UTM zone is just an extension of that distortion. You can > >> compute the precise distance error if you want for the furthest points > >> by comparing with the geodesic distance. > >> > >> Alternatively you might find there is a coordinate system that spans > >> your dataset nicely - often when a country or an island or a region > >> crosses UTM zones there is an official coordinate system defined that > >> is used by the authorities there. > >> > >> Also alternatively, there's nothing to stop you defining a transverse > >> mercator system based on the centre of your data. > >> > >> Barry > >> > >> > >> > >> On Fri, Mar 27, 2015 at 7:44 AM, moses selebatso < > [email protected]> > >> wrote: > >>> Hello > >>> I have animal movement data that I have converted from Lat/Long to UTM, > >> unfortunately the data falls in two UTM zones (34S and 35S). For some > >> reason R cannot display both of them in the same window (the 35S data is > >> way off the expected location). > >>> The question is how do I convert the data such that R can correctly > read > >> it? > >>> Moses SELEBATSO > >>> > >>> (+267) 318 5219 (H) (+267) 716 393 70 (C) > >>> (+267) 738 393 70 (C > >>> [[alternative HTML version deleted]] > >>> > >>> _______________________________________________ > >>> R-sig-Geo mailing list > >>> [email protected] > >>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo > >> > >> _______________________________________________ > >> R-sig-Geo mailing list > >> [email protected] > >> https://stat.ethz.ch/mailman/listinfo/r-sig-geo > > > > [[alternative HTML version deleted]] > > > > _______________________________________________ > > R-sig-Geo mailing list > > [email protected] > > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > [[alternative HTML version deleted]] _______________________________________________ R-sig-Geo mailing list [email protected] https://stat.ethz.ch/mailman/listinfo/r-sig-geo
