[R-sig-Geo] Migrating from proj strings to WKT/EPSG

[Diego Hernangómez Herrero]

Hi Ben:

I don't know if this is relevant for your question, but you can use
proj4strings with sf::st_crs() without using rgdal:

``` r
proj <- "+proj=tmerc +datum=NAD83 +lon_0=-70d10 lat_0=42d50
k=.9999666666666667 x_0=900000 y_0=0"
sf::st_crs(proj)

#> Coordinate Reference System:
#>   User input: +proj=tmerc +datum=NAD83 +lon_0=-70d10 lat_0=42d50
k=.9999666666666667 x_0=900000 y_0=0
#>   wkt:
#> PROJCRS["unknown",
#>     BASEGEOGCRS["unknown",
#>         DATUM["North American Datum 1983",
#>             ELLIPSOID["GRS 1980",6378137,298.257222101,
#>                 LENGTHUNIT["metre",1]],
#>             ID["EPSG",6269]],
#>         PRIMEM["Greenwich",0,
#>             ANGLEUNIT["degree",0.0174532925199433],
#>             ID["EPSG",8901]]],
#>     CONVERSION["unknown",
#>         METHOD["Transverse Mercator",
#>             ID["EPSG",9807]],
#>         PARAMETER["Latitude of natural origin",42.8333333333333,
#>             ANGLEUNIT["degree",0.0174532925199433],
#>             ID["EPSG",8801]],
#>         PARAMETER["Longitude of natural origin",-70.1666666666667,
#>             ANGLEUNIT["degree",0.0174532925199433],
#>             ID["EPSG",8802]],
#>         PARAMETER["Scale factor at natural origin",0.999966666666667,
#>             SCALEUNIT["unity",1],
#>             ID["EPSG",8805]],
#>         PARAMETER["False easting",900000,
#>             LENGTHUNIT["metre",1],
#>             ID["EPSG",8806]],
#>         PARAMETER["False northing",0,
#>             LENGTHUNIT["metre",1],
#>             ID["EPSG",8807]]],
#>     CS[Cartesian,2],
#>         AXIS["(E)",east,
#>             ORDER[1],
#>             LENGTHUNIT["metre",1,
#>                 ID["EPSG",9001]]],
#>         AXIS["(N)",north,
#>             ORDER[2],
#>             LENGTHUNIT["metre",1,
#>                 ID["EPSG",9001]]]]
```


El lun, 22 nov 2021 a las 20:11, Ben Tupper (<btupper using bigelow.org>)
escribió:

> Hello,
>
> I have a spatial mesh that provides the following CRS.
>
> proj <- "proj=tmerc +datum=NAD83 +lon_0=-70d10 lat_0=42d50
> k=.9999666666666667 x_0=900000 y_0=0"
>
> To use this with the sf package it must be formed as Well Known Text
> or a EPSG code. In this particular case there is no EPSG code in the
> registry.
>
> My current workflow so I can use this data in sf is to leverage
> showWKT() from the rgdal package to cast the proj string to WKT. The
> following message is printed when the packages is loaded.
>
> > Please note that rgdal will be retired by the end of 2023, plan
> transition to sf/stars/terra functions using GDAL and PROJ at your earliest
> convenience.
>
>
> rgdal::showWKT(proj) |> sf::st_crs(wkt)
>
> #> Coordinate Reference System:
> #>   User input:
>
> PROJCS["unknown",GEOGCS["unknown",DATUM["North_American_Datum_1983",SPHEROID["GRS
>
> 1980",6378137,298.257222101,AUTHORITY["EPSG","7019"]],AUTHORITY["EPSG","6269"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",42.8333333333333],PARAMETER["central_meridian",-70.1666666666667],PARAMETER["scale_factor",0.999966666666667],PARAMETER["false_easting",900000],PARAMETER["false_northing",0],UNIT["metre",1,AUTHORITY["EPSG","9001"]],AXIS["Easting",EAST],AXIS["Northing",NORTH]]
> #>   wkt:
> #> PROJCRS["unknown",
> #>     BASEGEOGCRS["unknown",
> #>         DATUM["North American Datum 1983",
> #>             ELLIPSOID["GRS 1980",6378137,298.257222101,
> #>                 LENGTHUNIT["metre",1]],
> #>             ID["EPSG",6269]],
> #>         PRIMEM["Greenwich",0,
> #>             ANGLEUNIT["degree",0.0174532925199433],
> #>             ID["EPSG",8901]]],
> #>     CONVERSION["unnamed",
> #>         METHOD["Transverse Mercator",
> #>             ID["EPSG",9807]],
> #>         PARAMETER["Latitude of natural origin",42.8333333333333,
> #>             ANGLEUNIT["degree",0.0174532925199433],
> #>             ID["EPSG",8801]],
> #>         PARAMETER["Longitude of natural origin",-70.1666666666667,
> #>             ANGLEUNIT["degree",0.0174532925199433],
> #>             ID["EPSG",8802]],
> #>         PARAMETER["Scale factor at natural origin",0.999966666666667,
> #>             SCALEUNIT["unity",1],
> #>             ID["EPSG",8805]],
> #>         PARAMETER["False easting",900000,
> #>             LENGTHUNIT["metre",1],
> #>             ID["EPSG",8806]],
> #>         PARAMETER["False northing",0,
> #>             LENGTHUNIT["metre",1],
> #>             ID["EPSG",8807]]],
> #>     CS[Cartesian,2],
> #>         AXIS["easting",east,
> #>             ORDER[1],
> #>             LENGTHUNIT["metre",1,
> #>                 ID["EPSG",9001]]],
> #>         AXIS["northing",north,
> #>             ORDER[2],
> #>             LENGTHUNIT["metre",1,
> #>                 ID["EPSG",9001]]]]
>
> In the spirit of not leaving things to the last minute (that's never
> happened before!), what are the current options for converting proj
> strings to WKT that don’t use rgdal?
>
> Cheers and thanks,
> Ben
>
> --
> Ben Tupper (he/him)
> Bigelow Laboratory for Ocean Science
> East Boothbay, Maine
> http://www.bigelow.org/
> https://eco.bigelow.org
>
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>


-- 



Have a nice day!

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