Hi, In JTS revision 637, Martin took care of the successive byte order
"Fixed WKBReader to handle successive geometrys with different endianness" http://jts-topo-suite.svn.sourceforge.net/viewvc/jts-topo-suite/trunk/jts/java/src/com/vividsolutions/jts/io/WKBReader.java?r1=57&r2=637Maybe there is also something with SRID handling, but I don't think so as it would make no difference between simple and multiple geometries.
Michaël
Hi Ede,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...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.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 )Michaëlall of this seems to be implemented in spatiallite as described below. so are we totally sure that JTS is not buggy in this regard? after all it reads like WKB analogue to WKT is supposed to be the cross platform implemented identically everywhere standard. ..ede PS: i'd really like to compare On 21.04.2013 14:14,edgar.sol...@web.de wrote:regarding your interpretation below i just found the following http://www.gaia-gis.it/spatialite-2.1/SpatiaLite-manual.html#t3.2 which states: " The Well-Known Binary (WKB) representation for geometric values is defined by the OpenGIS specification. " and " Component representation is as follows: The byte order ... The WKB type is represented as a four-bytes unsigned integer ... SNIP Collection type geometries [MultiPoint, MultiLineString, MultiPolygon and GeometryCollections] value has: the number of entities, represented as a four-bytes unsigned integer. a corresponding array of Points, LineStrings or Polygons as needed *note that each elementary entity has to be prefixed by its own WKB type.* " both informations together suggest to me that A) they claim to be standard conform B) the mysterious bytevalue is in fact a WKB type representation for the following WKB /additionally/ selecting geometries AsText() should result in WKTs, as far as i read page 2-29 of http://portal.opengeospatial.org/files/?artifact_id=829 maybe this helps.. ede On 15.04.2013 08:44, Michaël Michaud wrote:Hi, Just compared both strings to the spec, First string follows the WKB specification 01 endianess 06000000 MultiPolygon 02000000 Number of Polygons 01 endianess 03000000 Polygon 02000000 Two rings 04000000 Four points ... Second string follows the Spatialite specification http://www.gaia-gis.it/gaia-sins/BLOB-Geometry.html 01 endianess 06000000 MultiPolygon 02000000 Number of Polygons 69 Spatialite mark starting a new Geometry 03000000 Polygon 02000000 Two Rings 04000000 Four points In spatialite geometry description, endianess is not repeated for each component, instead, the 69 byte appears Probably the previous version of JTS could accomodate this because the byte order information is generally redundant, but a more strict parser will find a non authorized description for the Polygon as it does not start by the byte order. This means that the spatialite parser which just skipped the first bytes, then read the following byte stream as a wkb byte array with JTS must read each component as a Spatialite Geometry starting with 69. Michaël On Sun, Apr 14, 2013 at 3:39 PM, Rahkonen Jukka <jukka.rahko...@mmmtike.fi <mailto:jukka.rahko...@mmmtike.fi>> wrote: Hi, I made two tests: 1) With PostGIS 2.1 select encode(ST_AsBinary(ST_GeomFromText('MULTIPOLYGON(((0 0, 10 20, 30 40, 0 0), (1 1, 2 2, 3 3, 1 1)), ((100 100, 110 110, 120 120, 100 100)))')), 'hex') Query gives the same WKB that you used in JTS bug #3610843, that is "0106000000020000000103000000020000000400000000000000000000000000000000000000000000000000244000000000000034400000000000003e4000000000000044400000000000000000000000000000000004000000000000000000f03f000000000000f03f0000000000000040000000000000004000000000000008400000000000000840000000000000f03f000000000000f03f01030000000100000004000000000000000000594000000000000059400000000000805b400000000000805b400000000000005e400000000000005e4000000000000059400000000000005940" 2) With Spatialite select GeomFromWKB(x'0106000000020000006903000000020000000400000000000000000000000000000000000000000000000000244000000000000034400000000000003E4000000000000044400000000000000000000000000000000004000000000000000000F03F000000000000F03F0000000000000040000000000000004000000000000008400000000000000840000000000000F03F000000000000F03F69030000000100000004000000000000000000594000000000000059400000000000805B400000000000805B400000000000005E400000000000005E4000000000000059400000000000005940') Query creates a multipolygon geometry. Jukka, these two WKB hex strings differ around the 20th character: 01060000000200000001030 01060000000200000069030 The second one is the one I retrieved from spatialite. When I try to parse the second one with Postgis (1.5.3), I get an error: select ST_GeomFromWkb(decode('0106000000020000006903000000020000000400000000000000000000000000000000000000000000000000244000000000000034400000000000003E4000000000000044400000000000000000000000000000000004000000000000000000F03F000000000000F03F0000000000000040000000000000004000000000000008400000000000000840000000000000F03F000000000000F03F69030000000100000004000000000000000000594000000000000059400000000000805B400000000000805B400000000000005E400000000000005E4000000000000059400000000000005940', 'hex')); ERROR: invalid WKB type HINT: You must specify a valid OGC WKT geometry type such as POINT, LINESTRING or POLYGON I haven't manually verified the WKB, but it might be that spatialite is generating an invalid WKB, and JTS 1.12 was more forgiving about it than 1.13 is. -lreederTherefore it looks like the WKB is ok. But I do not understand that if PostGIS gives exactly the same WKB, how it is possible that OpenJUMP works with PostGIS but not with Spatialite through DB Query plugin? -Jukka Rahkonen------------------------------------------------------------------------------- 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------------------------------------------------------------------------------ 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------------------------------------------------------------------------------ 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------------------------------------------------------------------------------ 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------------------------------------------------------------------------------ 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
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