The problem described below has been corrected ins sp 1.2-4 which is now on CRAN; new releases of gstat, spgwr and spdep will follow to correct for the same bug.
On 08/12/16 15:48, Edzer Pebesma wrote: > While building support for geosphere distance functions in sf and > comparing results from geosphere::distMeeuws with those of sp::spDists, > I found a typo in the C code underlying the great circle distance > computation functions in sp (sp::spDists, sp::spDistsN1) [*]: > > https://github.com/edzer/sp/commit/d8374ff7efc6735cba9a054748c602bed0672f23 > > Before: >> library(sf) > Linking to GEOS 3.5.0, GDAL 2.1.0, proj.4 4.9.2 >> library(sp) >> library(units) >> >> x = st_sfc( > + st_point(c(0,0)), > + st_point(c(1,0)), > + st_point(c(2,0)), > + st_point(c(3,0)), > + crs = 4326 > + ) >> >> y = st_sfc( > + st_point(c(0,10)), > + st_point(c(1,0)), > + st_point(c(2,0)), > + st_point(c(3,0)), > + st_point(c(4,0)), > + crs = 4326 > + ) >> >> st_distance(x, y) > Units: m > [,1] [,2] [,3] [,4] [,5] > [1,] 1105855 111319.5 222639.0 333958.5 445278.0 > [2,] 1111387 0.0 111319.5 222639.0 333958.5 > [3,] 1127822 111319.5 0.0 111319.5 222639.0 > [4,] 1154693 222639.0 111319.5 0.0 111319.5 >> >> d.sf = st_distance(x, y, geosphere::distMeeus) >> d.sp = spDists(as(x, "Spatial"), as(y, "Spatial")) >> units(d.sp) = make_unit("km") >> d.sf - d.sp > Units: m > [,1] [,2] [,3] [,4] [,5] > [1,] 1851.990 0.000000e+00 0.000000e+00 0.000000e+00 0 > [2,] 1842.938 0.000000e+00 0.000000e+00 2.910383e-11 0 > [3,] 1816.564 0.000000e+00 0.000000e+00 1.455192e-11 0 > [4,] 1775.032 2.910383e-11 1.455192e-11 0.000000e+00 0 >> > > > > After: > >> library(sf) > Linking to GEOS 3.5.0, GDAL 2.1.0, proj.4 4.9.2 >> library(sp) >> library(units) >> >> x = st_sfc( > + st_point(c(0,0)), > + st_point(c(1,0)), > + st_point(c(2,0)), > + st_point(c(3,0)), > + crs = 4326 > + ) >> >> y = st_sfc( > + st_point(c(0,10)), > + st_point(c(1,0)), > + st_point(c(2,0)), > + st_point(c(3,0)), > + st_point(c(4,0)), > + crs = 4326 > + ) >> >> st_distance(x, y) > Units: m > [,1] [,2] [,3] [,4] [,5] > [1,] 1105855 111319.5 222639.0 333958.5 445278.0 > [2,] 1111387 0.0 111319.5 222639.0 333958.5 > [3,] 1127822 111319.5 0.0 111319.5 222639.0 > [4,] 1154693 222639.0 111319.5 0.0 111319.5 >> >> d.sf = st_distance(x, y, geosphere::distMeeus) >> d.sp = spDists(as(x, "Spatial"), as(y, "Spatial")) >> units(d.sp) = make_unit("km") >> d.sf - d.sp > Units: m > [,1] [,2] [,3] [,4] [,5] > [1,] -2.328306e-10 0.000000e+00 0.000000e+00 0.000000e+00 0 > [2,] 2.328306e-10 0.000000e+00 0.000000e+00 2.910383e-11 0 > [3,] 0.000000e+00 0.000000e+00 0.000000e+00 1.455192e-11 0 > [4,] 0.000000e+00 2.910383e-11 1.455192e-11 0.000000e+00 0 >> > > [*] assuming the source code of > http://www.abecedarical.com/javascript/script_greatcircle.html is > correct; I don't have access to the Meeuws book mentioned there under (1). > > The same C function is used by gstat; I corrected that as well. > > > > _______________________________________________ > R-sig-Geo mailing list > R-sig-Geo@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > -- Edzer Pebesma Institute for Geoinformatics (ifgi), University of Münster Heisenbergstraße 2, 48149 Münster, Germany; +49 251 83 33081 Journal of Statistical Software: http://www.jstatsoft.org/ Computers & Geosciences: http://elsevier.com/locate/cageo/
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