Hello Adam
Le 16/10/13 05:17, Adam Estrada a écrit :
I like #3 as well. It's simple and makes sense. I would like to hear from
Joe White on this as he has an intimate knowledge of Proj4 and how it's
implemented in GDAL. Joe, what would you would have wanted to see in
previous projects?
On my side, I have a somewhat superficial knowledge of Proj.4. Last time
I looked at the API (when I wrote the Proj.4 - GeoAPI JNI bindings), I
didn't noticed pre-defined constants. I noticed two ways to create a CRS
in Proj.4:
* Either by specifying the CRS definition as a String in the Proj.4
syntax. In Apache SIS, that would be conceptually equivalent to
using a CRSFactory [1].
* Either by specifying the EPSG code, in which case Proj.4 looks for
the definition String in a file. In Apache SIS, that would be
conceptually equivalent to using a CRSAuthorityFactory [2]. For
making this task easier, a convenience static method would be
provided [3].
A difference between Proj.4 and Apache SIS is that the Proj.4 project
exported some tables from the EPSG database to a plain text file, while
Apache SIS would connect directly to a local copy of the full EPSG
database using JDBC. Advantage of the full database is that we get more
information (accuracy estimation, aliases, area of validity,
transformation paths, etc.). Inconvenient is that we are more a risk
that something goes wrong while using JDBC (e.g. corrupted database).
Thus the idea to select a small subset of CRS to declare as constants
not only for convenience, but also for providing the guarantee that a
minimal definition of those CRS will always be available no matter what
happen with the local copy of the EPSG database. I think that there is
less incentive for that approach in Proj.4...
Martin
[1]
http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/crs/CRSFactory.html
[2]
http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/crs/CRSAuthorityFactory.html
[3]
https://builds.apache.org/job/sis-jdk7/site/apidocs/org/apache/sis/referencing/CRS.html#forCode%28java.lang.String%29
