On 21.04.2013 15:46, Michaël Michaud wrote: > Hi Ede, >> ok, just dug some more into "OpenGIS Simple Features Specification for SQL" >> http://portal.opengeospatial.org/files/?artifact_id=829 >> >> and as far as i read on page 3-24 and later, a little bit unclear, but it >> seems to me that endianess is not repeated (see the Polygon example with >> /two/ rings) but left away. for multi geometries the standard expects the >> sub geometries first value is the wkb type. > My interpretation of p 3-26 is that MultiPolygon has a byte order, a wkbtype > (6), a number of polygons, then an array of polygons, *each polygon having in > turn a byte order*, a wkbtype (3), a number of ring... > So yes, I think the byte order is repeated and sub-geometries do not starts > with geometry type. The example with the polygon made of two rings is another > thing as it is not a multi-geometry. > In spatialite, after the number of entities (polygons) in a collection comes > a byte mark (hex=69), the geometry type, the geometry class specific... > > As a result, the byte number should be the same, and the only difference is > that each simple geometry starts with a byte order in wkb and with 0x69 in > spatialite, which could explain that JTS 1.12 did read spatialite geometry if > it just ignored this particular byte which is not very useful (one must be > particularly vicious to change byete order inside a single multigeometry > object ) >
now that you explain it again, i agree fully. i couldn't find the skipping of the byte in com\vividsolutions\jts\io\WKBReader.java though. but the approach sounds conclusive. ..ede ------------------------------------------------------------------------------ Precog is a next-generation analytics platform capable of advanced analytics on semi-structured data. The platform includes APIs for building apps and a phenomenal toolset for data science. Developers can use our toolset for easy data analysis & visualization. Get a free account! http://www2.precog.com/precogplatform/slashdotnewsletter _______________________________________________ Jump-pilot-devel mailing list Jump-pilot-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel
