Thomas, I do not think it is wishful thinking. Au contraire, I think it is how it should be done. That is, if you start with a longitude/latitude raster with elevation values, and want slopes (or similar) also in that coordinate reference system, then this should be the way to go, as you skip two transformations, each of which would lead to data quality loss. Robert
((for the record, the question is about computing slopes from raster data with a longitude/latitude (angular) coordinate reference system ---- the datum 'WGS 84' is not relevant, as projected data also use that datum)) On Wed, Aug 12, 2015 at 10:44 AM, Stanley, Thomas A. (GSFC-617.0)[USRA] <thomas.a.stan...@nasa.gov> wrote: > At https://rpubs.com/ajlyons/rspatialdata, a presentation shows the raster > package's terrain function used directly on an unprojected raster near the > Equator. I'd love to skip the steps of projecting and unprojecting my DEM > tiles (eg http://www.viewfinderpanoramas.org/dem3/M11.zip), but I'm not sure > the function is intended to be used in WGS 84 for all locations. The output > values certainly look good. Can I correctly calculate slope without > projecting my tiles, or is that wishful thinking? > > -Thomas > > [[alternative HTML version deleted]] > > _______________________________________________ > R-sig-Geo mailing list > R-sig-Geo@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-geo _______________________________________________ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo