Thank you, it worked perfectly On Thu, Oct 17, 2019 at 3:31 PM Martin Desruisseaux < martin.desruisse...@geomatys.com> wrote:
> Hello Thierry! > > Le 17/10/2019 à 20:06, Thierry Danard a écrit : > > I recently started to use Apache SIS. It was fairly easy to learn how to > convert between two coordinate systems. However, my application requires > the precision brought by the use of NADCON and NTV2 grid shifts. I do see > in the logs the following warnings when I perform a coordinate conversion: > > Oct 17, 2019 12:36:32 PM > org.apache.sis.referencing.operation.CoordinateOperationFinder > createOperations > WARNING: Can not parse “NTv2_0.gsb” as a file in the NTv2 format. > (...snip...) > > I do have a copy of all .las, .los and .gsb files. My first question is: > where does Apache SIS expect these files to be located? > > For data files like datum grids, SIS needs a directory where the data will > be located. This directory can be located anywhere on your machine. Its > location is specified by the SIS_DATA environment variable. On Linux and > MacOS systems, this environment variable can be set on the command-like as > below: > > export SIS_DATA=/path/to/a/directory > > On Windows systems, I think the command is "set" instead of "export". > > The directory pointed by the SIS_DATA environment variable must exist; > SIS will not create it in order to avoid touching the system without user > knowledge. For the same reason, there is currently no default directory is > SIS_DATA is not set. > > The ".los", ".las" and ".gsb" can be put in a sub-directory of above > directory with exactly this name (including upper-cases): > > DatumChanges/ > > By the way, SIS can also use this directory for the EPSG dabase > <http://sis.apache.org/epsg.html#maven-epsg>. Using that directory + > sis-epsg Maven artifact is faster than using the sis-embedded-data Maven > artifact. Just having the SIS_DATA variable defined and the sis-epsg > Maven artifact available on the classpath (instead of sis-embedded-data) > is sufficient; SIS will create a local copy of the EPSG database in that > directory automatically. > > The org.apache.sis.internal.referencing.provider.NADCON class only > references one grid (the conus grid, defined by conus.los and conus.las > files). How do I add other NADCON grids (ex: alaska) ? Should I modify the > code of the NADCON class to take into account my other NADCON grid files ? > > There is no need to change the code. Just put all files in above-cited <value > of SIS_DATA>/DatumChanges/ directory and it should work. SIS gets the > name of datum shift grid from the EPSG database. In order to instruct SIS > to use the grid for Alaska, use the CRS.findOperation static method > <http://sis.apache.org/apidocs/org/apache/sis/referencing/CRS.html#findOperation(org.opengis.referencing.crs.CoordinateReferenceSystem,org.opengis.referencing.crs.CoordinateReferenceSystem,org.opengis.metadata.extent.GeographicBoundingBox)> > with the areaOfInterest argument set to a bounding box over Alaska. Same > apply for other regions of the world. > > In order to verify if the datum grid files are used, just print the > CoordinateOperation to the console: > > System.out.println(theOperation); > > Check the PARAMETER elements in the output string. You should see > parameter with the grid file names in it. > > Please let us know if there is any issue, > > Regards, > > Martin > > >
