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

[Markus Metz]

On Fri, Nov 10, 2017 at 6:43 PM, Markus Metz <markus.metz.giswork at gmail.com>
wrote:
>
>
>
> 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.

Fixed in trunk r71656.

The test for different datum names has been disabled again in trunk r71657.
There are several different datum names in lib/gis/datum.table that
apparently mean the same: same ellipsoid and same transformation
parameters. Apparently, GRASS does not provide a datum name when converting
projection information from GRASS to proj4 for reprojecting data.

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
> >
> > _______________________________________________
> > grass-dev mailing list
> > grass-dev at lists.osgeo.org
> > https://lists.osgeo.org/mailman/listinfo/grass-dev
>
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