Since this topic is of general interest, I've made an exception and allowed (this once!) a posting of more than 200K. In general, if graphics are big, please consider either an alternative device (png is often OK), or posting just a URL to the real file.
With apologies to list members on dial-up connections in the field, Roger On Thu, 5 Apr 2007 [EMAIL PROTECTED] wrote: > Yes, for many uses that is my choice also. For the conterminous US for > example, the Lambert azimuthal has lower mean distortion than the > commonly used standard projection, the Albers conical equal area, > although Albers was chosen by USGS as a standard because of lower > extreme distortion than many other possible projections. > > For our hemispherical application, because we were gridding the data, we > wanted parallels of latitude to be parallel in the projected coordinate > space, which we wouldn't get with the Lambert azimuthal. > > (See attached file: whemi.projs.pdf) > > Tim Keitt <[EMAIL PROTECTED]> wrote on 2007-04-05 10:56:09: > > > Thanks. My application is not that demanding. Really, I just want it > > to look reasonable. My plan is to lay out the postings in the > > projected coordinates and then back transform into geographic > > coordinates for analysis. I tried lots of projections and found > > Lamberts Azimuthal Equal Area to be quite good. I like the look of the > > Azimuthal Equidistant better, but figured equal area was a good > > choice. > > > > THK > > > > On 4/4/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> > wrote: > > > Tim, > > > > > > It depends on which kind of distortion is of most concern. For many > > > types of extensive data, especially counts, for example, the equal > area > > > property is desirable. We used the Lambert cylindrical equal area > > > projection with standard parallels of +/- 30 degrees for some > western > > > hemispherical work, see reference below. (The center longitude > could be > > > -80 west, but that is less important than the choice of parallels.) > > > > > > Before falling back on the Lambert as an easy to use projection, I > tried > > > to get several ESRI products to implement an interrupted projection > > > using the sinusoidal projection, in part for reasons given in the > second > > > reference. I used a separate center longitude for north and south > of > > > the equator and the appearance is certainly more satisfactory than > the > > > Lambert in my opinion. I'll attach a PDF of an illustration of this > > > approach generated in R that I hope you will get but not the rest of > the > > > list unfortunately. I can send PDFs of the references also if > needed. > > > > > > Denis > > > > > > Lawler JJ, White D, Neilson RP, Blaustein AR. 2006. Predicting > > > climate-induced range shifts: model differences and model > reliability. > > > Global Change Biology 12:1568-1584. > > > > > > White D. 2006. Display of pixel loss and replication in > reprojecting > > > raster data from the sinusoidal projection. Geocarto International > > > 21(2):19-22. > > > > > > (See attached file: whemi.sinus.pdf) > > > > > > [EMAIL PROTECTED] wrote on 2007-04-04 12:17:39: > > > > > > > Anyone know of a particularly good map projection for showing all > of > > > > North and South America without too much distortion? > > > > > > > > THK > > > > > > > > -- > > > > Timothy H. Keitt, University of Texas at Austin > > > > Contact info and schedule at http://www.keittlab.org/tkeitt/ > > > > Reprints at http://www.keittlab.org/tkeitt/papers/ > > > > ODF attachment? See http://www.openoffice.org/ > > > > > > > > _______________________________________________ > > > > R-sig-Geo mailing list > > > > R-sig-Geo@stat.math.ethz.ch > > > > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > > > > > > > > > -- > > Timothy H. Keitt, University of Texas at Austin > > Contact info and schedule at http://www.keittlab.org/tkeitt/ > > Reprints at http://www.keittlab.org/tkeitt/papers/ > > ODF attachment? See http://www.openoffice.org/ -- Roger Bivand Economic Geography Section, Department of Economics, Norwegian School of Economics and Business Administration, Helleveien 30, N-5045 Bergen, Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43 e-mail: [EMAIL PROTECTED] _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo