[GRASS-dev] Different CRS matching in 7.2 and trunk

[Markus Metz]

On Fri, Nov 10, 2017 at 6:08 PM, Vaclav Petras <wenzeslaus at gmail.com> wrote:
>
> Hi all,
>
> I'm trying to understand a change of behavior between 7.2 and trunk. With
7.2, I can do the following:
>
> curl -SL http://fatra.cnr.ncsu.edu/foss4g2017/nc_tile_0793_016_spm.zip \
>     > nc_tile_0793_016_spm.zip  && unzip nc_tile_0793_016_spm.zip
>
> grass72 -c EPSG:3358 ~/grassdata/crs_test -e
> grass72 ~/grassdata/crs_test2/PERMANENT/ --exec r.in.lidar
input=nc_tile_0793_016_spm.las output=count_10 method=n -e -n resolution=10
>
> The last step (r.in.lidar) fails in current trunk because the projection
don't match. Here is the difference (name, datum and swapped lat_1 and
lat_2):
>
>        GRASS LOCATION PROJ_INFO is:
>        name: NAD83(HARN) / North Carolina
>        datum: nad83harn
>        lat_1: 36.16666666666666
>        lat_2: 34.33333333333334
>
>        Import dataset PROJ_INFO is:
>        name: NAD_1983_StatePlane_North_Carolina_FIPS_3200
>        datum: nad83
>        lat_1: 34.33333333333334
>        lat_2: 36.16666666666666
>
> 7.2 considers this OK while trunk considers this different. I'm not sure
which one is correct.

In this case, 7.2 is correct, but 7.2 does not compare datums, i.e.
projections would be regarded as matching even with e.g. nad27 and nad83.
The comparison of datums is new in 7.3 and needs some refinement.

I will fix the comparison of swapped lat_1 and lat_2.

Markus M


>
> Here is the lasinfo reference:
>
> PROJCS["NAD_1983_StatePlane_North_Carolina_FIPS_3200",
>     GEOGCS["GCS_North_American_1983",
>         DATUM["North_American_Datum_1983",
>             SPHEROID["GRS_1980",6378137,298.257222101]],
>         PRIMEM["Greenwich",0],
>         UNIT["Degree",0.0174532925199432955]],
>     PROJECTION["Lambert_Conformal_Conic_2SP"],
>     PARAMETER["False_Easting",609601.22],
>     PARAMETER["False_Northing",0],
>     PARAMETER["Central_Meridian",-79],
>     PARAMETER["Standard_Parallel_1",34.33333333333334],
>     PARAMETER["Standard_Parallel_2",36.16666666666666],
>     PARAMETER["Latitude_Of_Origin",33.75],
>     UNIT["Meter",1]]
>
> `r.in.lidar -p` in both 7.2 and trunk gives:
>
> +proj=lcc +lat_1=34.33333333333334 +lat_2=36.16666666666666 +lat_0=33.75
+lon_0=-79 +x_0=609601.22 +y_0=0 +datum=NAD83 +units=m +no_defs
>
> `g.proj -p` gives the following in 7.2 and trunk in locations created by
7.2 and trunk:
>
> -PROJ_INFO-------------------------------------------------
> name       : NAD83(HARN) / North Carolina
> datum      : nad83harn
> ellps      : grs80
> proj       : lcc
> lat_1      : 36.16666666666666
> lat_2      : 34.33333333333334
> lat_0      : 33.75
> lon_0      : -79
> x_0        : 609601.22
> y_0        : 0
> no_defs    : defined
> -PROJ_EPSG-------------------------------------------------
> epsg       : 3358
> -PROJ_UNITS------------------------------------------------
> unit       : meter
> units      : meters
> meters     : 1
>
> I don't know how to resolve it besides using -o but I don't know how to
justify it and why there is a difference (I don't see it in the recent
proj-related commits).
>
> Thank you,
> Vaclav
>
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