[R] sp:gIntersection warning message about projection

[Bert Gunter]

Probably better asked on the r-sig-geo list, which is specifically for
spatial statistics.

Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Tue, Oct 20, 2020 at 6:38 AM Robert Lovejoy <monicapalalovejoy using gmail.com>
wrote:

> Hi,
>
> I am using in my workflow gIntersection from sp package. Part of my
> relevant sessionInfo is:
> R version 4.0.3 (2020-10-10)
> Platform: x86_64-w64-mingw32/x64 (64-bit)
> Running under: Windows 10 x64 (build 17763)
>
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
>
> other attached packages:
> [1] CircStats_0.2-6 boot_1.3-25     MASS_7.3-53     stringr_1.4.0
> [5] rgeos_0.5-5     maptools_1.0-2  rgdal_1.5-18    raster_3.3-13
> [9] sp_1.4-4
>
>
> So i am using 2  SpatialLinesDataFrame that are results of previous
> computation. I am not sure i can give a viable examples, but maybe this can
> be solved without. If not i will figure out how i can give you a workable
> example. Or if you know if there are in R already loaded 2 different line
> shapefiles with projection then i will see if i can replicate this problem.
>
> So, first file:
>  buff
> class       : SpatialLinesDataFrame
> features    : 1
> extent      : 560525.5, 561302.4, 4698908, 4701110  (xmin, xmax, ymin,
> ymax)
> crs         : +proj=utm +zone=16 +datum=WGS84 +units=m +no_defs
> variables   : 2
> names       : ID, buff_dist
> value       :  2,       135
>
> second file:
>
> pln
> class       : SpatialLinesDataFrame
> features    : 1
> extent      : 560615.6, 560705.4, 4698905, 4699180  (xmin, xmax, ymin,
> ymax)
> crs         : +proj=utm +zone=16 +datum=WGS84 +units=m +no_defs
> variables   : 2
> names       :                x,                y
> value       : 560615.564407584, 4698904.71208346
>
> Please observe that both files have identical projections.
>
> p1 <- gIntersection(buff, pln)
> Warning message:
> In RGEOSBinTopoFunc(spgeom1, spgeom2, byid, id, drop_lower_td,
> unaryUnion_if_byid_false,  :
>   spgeom1 and spgeom2 have different proj4 strings
>
> This warning is baffling since both files have same projection:
> crs(buff)
> CRS arguments:
>  +proj=utm +zone=16 +datum=WGS84 +units=m +no_defs
>
> crs(pln)
> CRS arguments:
>  +proj=utm +zone=16 +datum=WGS84 +units=m +no_defs
>
> Probably i am doing something wrong but for the life of me i cannot see it
> as yet.
>
> Thanks so much for any help, take care,
> Monica
>
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>
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