Tag Archives: geometry

Boost.Geometry mailing list moved

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I have moved mailing list of the Boost.Geometry library from server at OSGeo to Boost mailing list server. All existing subscribers and archives have been moved to the new server.

The new list is available at geometry at lists dot boost dot org. It is also mirrored at Nabble as Boost.Geometry.

The old ggl at lists dot osgeo dot org will be wiped out soon.

If anyone experiences any problems with the new geometry at lists.boost.org, please contact me directly.

Big thanks to the OSGeo Foundation for hosting the ggl mailing list and thanks to Boost admins for help with the new server.

Update on SqlGeometry and POINT EMPTY in WKB

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Long time ago I discussed about how SqlGeometry handles POINT EMPTY in WKB format. The SqlGeometry states the definition of OGC GEOMETRY type for Microsoft SQL Server. Shortly, the message was that SqlGeometry implicitly casts POINT EMPTY to MULTIPOINT EMPTY geometry when generating WKB output. PostGIS casts as well, but does it in a consistent way, in my opinion, outputting GEOMETRYCOLLECTION.

Following those findings, I assumed it is not quite correct, or I didn’t like the inconsistency, and I had reported it to Microsoft Connect as a bug: SqlGeometry reports invalid type of WKB of POINT EMPTY.

Recently, I have received a couple of comments from Microsoft to my report. The comments are attached to the report linked above, but I paste them below for completeness and archive:

Our development team for the spatial data types tells me that it is not possible to use a single value for the WKB format of any spatial data type. For the POINT EMPTY, the WKB format does not allow empty points, so we are outputting a MULTIPOINT with zero elements.
In a MULTIPOINT EMPTY, we are stripping out empty points.

The reasoning is technically correct. It’s just Microsoft does it differently. However, as second comment suggests, the current behaviour may change in future:

But we might consider changing it to get consistent behavior.

Preparing for Subversion to Git migration

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GEOS is slowly moving to Git, so I decided to clear the Subversion specific settings, namely the svn:keywords. The procedure is quick and based on the commands I used to perform bulk svn:keywords property update.

First, svn:keywords property is removed:

find . -path '*/.svn' -prune -o -type f -print  | xargs svn propdel -q svn:keywords

Next, line consisting of $Id$ keyword is stripped from every plain text file using a tiny script coded in Python:


#! /usr/bin/env python
import fileinput
import re
import sys

def strip_line(filename, rx):
    sys.stderr.write(filename + '\n')
    for line in fileinput.input(filename, inplace=1):
        m = re.match(rx, line)
        if m is None:
            sys.stdout.write(line)
        else:
            sys.stderr.write(line)

if len(sys.argv) < 2:
    sys.exit("Missing filename")

pattern = '^.*\$Id.*$'
rx = re.compile(pattern, re.DOTALL)
strip_line(sys.argv[1], rx)

The script is executed for every file, excluding the working copy admin area in .svn:

for f in `find . -path '*/.svn' -prune -o -type f -print`; do ~/bin/strip_line_regex.py $f; done;

Voila!

Update: Torvalds answers Does GIT has vc keywords like CVS/Subversion?

Introduction to Boost Geometry slides

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Boost Geometry (aka Generic Geometry Library, GGL)Slides of my very gentle introduction to Boost Geometry library are now available to download from the FOSS4G 2010 website.

The presentation gives a basic overview of the library and tries to explain how it is different to existing solutions but in such way so it’s also understandable to non-C++ programmers. Those who are looking forward to digging out very details of Boost Geometry, I recommend to check presentation which Barend Gehrels gave at BoostCon 2010.

Boost.Geometry on BoostCon’10

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Boost Geometry (aka Generic Geometry Library, GGL)Boost.Geometry talk is scheduled for BoostCon’10 conference. Thanks to Barend Gehrels, Boost.Geometry team will be represented on the conference.

In spite of the fact I’m listed as a speaker for BoostCon’10, I will not attend this amazing event. I’ve planned to be there, I can’t make it this year, unfortunately.