Warning message: In showSRID(uprojargs, format = "PROJ", multiline = "NO")?

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Warning message: In showSRID(uprojargs, format = "PROJ", multiline = "NO")?

Michal Kvasnička
Hello.

I have a sfc_MULTILINESTRING object called zz. It is in CRS EPSG:5514
("S-JTSK / Krovak East North"). When I convert it to sp via as(zz,
"Spatial"), I get the following warning:

Warning message:
In showSRID(uprojargs, format = "PROJ", multiline = "NO") :
  Discarded datum Unknown based on Bessel 1841 ellipsoid in CRS definition,
 but +towgs84= values preserved

Could you help me understand what does this mean and whether it is serious?

I use:
R version 4.0.2 (2020-06-22)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 20.04 LTS
sf 0.9-5
sp 1.4-2
rgdal 1.5-12
rgeos 0.5-3
gdal 3.0.4
geos 3.8.0

Many thanks for your help.

Best wishes,
*Ing. Michal Kvasnička, Ph.D.*



*Masaryk University | School of Economics and Administration*
Department of Economics
A: Lipová 41a | 602 00 Brno
E: [hidden email] | W: www.econ.muni.cz/~qasar

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Re: Warning message: In showSRID(uprojargs, format = "PROJ", multiline = "NO")?

Roger Bivand
Administrator
It depends on your software and workflow. If you check the versions of PROJ and GDAL with rgdal::extSoftVersion(), you will probably find > 5 and > 2. If you then take sp::wkt() of the sp object, you should see a correct WKT2 representation of the CRS. Packages using this should not show degradation, but those only using the Proj4 string may show degradation. See https://rgdal.r-forge.r-project.org/articles/CRS_projections_transformations.html and
https://www.r-spatial.org/r/2020/03/17/wkt.html for details.

-------
Roger Bivand
Norwegian School of Economics, Bergen, Norway
[hidden email]

________________________________
Fra: R-sig-Geo <[hidden email]> p� vegne av Michal Kvasni�ka <[hidden email]>
Sendt: tirsdag 21. juli 2020, 16:08
Til: [hidden email]
Emne: [R-sig-Geo] Warning message: In showSRID(uprojargs, format = "PROJ", multiline = "NO")?

Hello. I have a sfc_MULTILINESTRING object called zz. It is in CRS EPSG:5514 ("S-JTSK / Krovak East North"). When I convert it to sp via as(zz, "Spatial"), I get the following warning: Warning message: In showSRID(uprojargs, format = "PROJ", multiline = "NO") : Discarded datum Unknown based on Bessel 1841 ellipsoid in CRS definition, but +towgs84= values preserved Could you help me understand what does this mean and whether it is serious? I use: R version 4.0.2 (2020-06-22) Platform: x86_64-pc-linux-gnu (64-bit) Running under: Ubuntu 20.04 LTS sf 0.9-5 sp 1.4-2 rgdal 1.5-12 rgeos 0.5-3 gdal 3.0.4 geos 3.8.0 Many thanks for your help. Best wishes, *Ing. Michal Kvasni�ka, Ph.D.* *Masaryk University | School of Economics and Administration* Department of Economics A: Lipov� 41a | 602 00 Brno E: [hidden email] | W: www.econ.muni.cz/~qasar [[alternative HTML version deleted]] _______________________________________________ R-sig-Geo mailing list [hidden email] https://stat.ethz.ch/mailman/listinfo/r-sig-geo

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Roger Bivand
Department of Economics
Norwegian School of Economics
Helleveien 30
N-5045 Bergen, Norway
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Re: Warning message: In showSRID(uprojargs, format = "PROJ", multiline = "NO")?

Michal Kvasnička
Hello.

Many thanks for your reply. I tried to read the two papers you suggested,
but I can't say I do understand them very well (I'm an economist, not a
geographer).

Do I understand it correctly that when I use just EPSG numbers and stay
away from proj4 string, and have up-to-date SW, I'd be safe?

I transform CRS with sf::st_transform(crs = 5514).

rgdal::rgdal_extSoftVersion() returns on my computers:
          GDAL GDAL_with_GEOS           PROJ             sp
       "3.0.4"         "TRUE"        "6.3.1"        "1.4-2"

rgdal::sp::wkt(sp) returns the same WKT as sf::st_crs(sf), where sf is the
original object and sp <- as(sf, "Spatial").

Are these sufficient tests sufficient to say I'm o.k.? Many thanks once
more for your time.

Best wishes,
*Ing. Michal Kvasnička, Ph.D.*



*Masaryk University | School of Economics and Administration*
Department of Economics
A: Lipová 41a | 602 00 Brno
E: [hidden email] | W: www.econ.muni.cz/~qasar


út 21. 7. 2020 v 17:32 odesílatel Roger Bivand <[hidden email]> napsal:

> It depends on your software and workflow. If you check the versions of
> PROJ and GDAL with rgdal::extSoftVersion(), you will probably find > 5 and
> > 2. If you then take sp::wkt() of the sp object, you should see a correct
> WKT2 representation of the CRS. Packages using this should not show
> degradation, but those only using the Proj4 string may show degradation.
> See
> https://rgdal.r-forge.r-project.org/articles/CRS_projections_transformations.html
>  and
> https://www.r-spatial.org/r/2020/03/17/wkt.html for details.
>
> -------
> Roger Bivand
> Norwegian School of Economics, Bergen, Norway
> [hidden email]
>
> ------------------------------
> *Fra:* R-sig-Geo <[hidden email]> på vegne av Michal
> Kvasnička <[hidden email]>
> *Sendt:* tirsdag 21. juli 2020, 16:08
> *Til:* [hidden email]
> *Emne:* [R-sig-Geo] Warning message: In showSRID(uprojargs, format =
> "PROJ", multiline = "NO")?
>
> Hello. I have a sfc_MULTILINESTRING object called zz. It is in CRS
> EPSG:5514 ("S-JTSK / Krovak East North"). When I convert it to sp via
> as(zz, "Spatial"), I get the following warning: Warning message: In
> showSRID(uprojargs, format = "PROJ", multiline = "NO") : Discarded datum
> Unknown based on Bessel 1841 ellipsoid in CRS definition, but +towgs84=
> values preserved Could you help me understand what does this mean and
> whether it is serious? I use: R version 4.0.2 (2020-06-22) Platform:
> x86_64-pc-linux-gnu (64-bit) Running under: Ubuntu 20.04 LTS sf 0.9-5 sp
> 1.4-2 rgdal 1.5-12 rgeos 0.5-3 gdal 3.0.4 geos 3.8.0 Many thanks for your
> help. Best wishes, *Ing. Michal Kvasnička, Ph.D.* *Masaryk University |
> School of Economics and Administration* Department of Economics A: Lipová
> 41a | 602 00 Brno E: [hidden email] | W:
> www.econ.muni.cz/~qasar [[alternative HTML version deleted]]
> _______________________________________________ R-sig-Geo mailing list
> [hidden email] https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>

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