Hi, Martin, That does look very convenient when using systems that share those common bits. +1
Joe On Tue, Jul 7, 2015 at 12:38 PM, Adam Estrada <[email protected]> wrote: > No comment from me, Martin. Looks good and thanks for the update... > > a > > On Tue, Jul 7, 2015 at 12:05 PM, Martin Desruisseaux > <[email protected]> wrote: > > Hello all > > > > The WKT 1 and 2 parser and formatter are now completed. I would like to > > propose an extension for making easier a common usage. Since this > > proposition is outside the scope of ISO 19162 standard, I would like to > > submit it for discussion. > > > > Among other usages, the WKT format is convenient for allowing users to > > define their own Coordinate Reference System (CRS) in addition to the > > ones published in the EPSG database. We can support this need with a > > file of (key,value) pairs, for example: > > > > myCRS1 = GeodeticCRS[... WKT description here ...] > > myCRS2 = GeodeticCRS[... other WKT description ...] > > myCRS3 = ProjectedCRS[... WKT description here ...] > > etc. > > > > However those files tend to be large with lot of redundancy. For example > > there is often many CRS using the same ellipsoid (typically WGS84). The > > proposal is to allow users to assign to a variable the value of a WKT > > fragment, and allow usage of such variables in larger WKT. The syntax > > would be similar to the use of environment variables in Unix: the "$" > > sign would mean "insert here the value of the variable". So if the > > following value is assigned to the "MyEllipsoid" variable: > > > > Ellipsoid[“Bessel 1841”, 6377397.155, 299.1528128] > > > > Then the following WKT: > > > > GeodeticCRS[“Tokyo”, Datum[“Tokyo”, *$MyEllipsoid*], ...rest of WKT > omitted...] > > > > Would be equivalent to: > > > > GeodeticCRS[“Tokyo”, Datum[“Tokyo”, Ellipsoid[“Bessel 1841”, > 6377397.155, 299.1528128]], ...rest of WKT omitted...] > > > > This syntax is already implemented for testing purpose (see "String > > expansion" in > > > https://builds.apache.org/job/sis-dev/javadoc/org/apache/sis/io/wkt/WKTFormat.html > ), > > but we could modify it if there is proposal to do otherwise. Does anyone > > have comment? > > > > Martin > > > > >
