Posts in category osgeo

NACIS 2009 Opening up

So at the AAG Conference last year, we ran an  OSGeo booth. Some representative from North American Cartographic Information Society ( NACIS) approached and invited us to their conference.(It wasn't the 1st time after one of my talks on FOSS previously I had been asked).

Now the important part, the California Chapter gave a 50 minute, 4 app demo at the NACIS "Practical Cartography Day" to an audience of 150.  Details Take home message - Cartographers want good svg output.

Notes from the rest of the conference, "Open" was actually mentioned a lot. Here's a rough breakdown of the frequency of relevant topics(In presentations):

  • Postgis ++
  • OpenLayers(not by name but showed up in slides and on demo sites) +++
  • mapnik ++
  • GDAL +
  • Modestmaps
  • php +++
  • OpenSource +++++(Even ESRI)
  • Python +++
  • OpenStreetmap ++++
  • Flash/Flex +++++++
  • OGC +
  • Inkscape +
  • GIMP +
  • WMS +

(Maybe I'll post a plot when I get chance)

Next post: Some new public domain datasets people are going to want to get their hands on...

Desktop Open Source goes mainstream, old school style

Gary Sherman's book in the UC Davis library Congratulations to Gary Sherman who's recent book has successfully made it to the shelves of academia. Well that might be in part to our librarian taking advice on what open source gis books are missing that should be on the shelf. Lucky for everyone else, since the publisher didn't classify it as a text book it's also affordable too if you want your own copy, paper or ebook.

Desktop GIS: Mapping the Planet with Open Source. Pragmatic Bookshelf, 360 pages, ISBN 1934356069,  http://www.pragprog.com/titles/gsdgis/desktop-gis

Wondering what other books you've missed see the  OSGeo Library

Network analysis using GRASS

I ended up wanting to analyze commute paths on several networks, but instructions on how to properly prepare a network file with new points snapped to it as nodes was a little less than clear. I'm not 100% sure this is right but it is pieced together from the command history  GRASS stored with each layer in my mapset. 

#bring the layer in
v.in.ogr -o dsn="/scratch/congelton/davis_ped_net/ped_net_sep28.shp" output="pednets28" min_area=0.0001 snap=-1

#find the nearest line to a point and create a line that connects them
v.distance -p from="davissubset@PERMANENT" to="pednetsep28" from_type="point" to_type="point,line,area" from_layer=1 to_layer=1 output="ppl2pednet" dmax=-1 upload="dist" column="dist"

#add categories to the distance lines(I think this is required otherwise v.net won't work later, if the cat column is already populated then you can skip this)
v.category input="ppl2pednet" output="ppl2pednetcat" type="point,line,boundary,centroid,area" option="add" cat=1 layer=1 step=1

#patch the distance lines to the to the original points, so you have the nodes for v.net
v.patch input="ppl2pednetcat,pednets28" output="pplpednet"

# patch the distance lines to the network
v.patch input="pplpednet,davissubset" output="pplonpednet"

#I ran a clean before I did the actual v.net command to make sure I dropped things that wouldn't work, outliers
v.clean input="pplonpednet" output="pplonpednetclean3" type="line,point" tool="snap,break" thresh=3,3

#run the network shortest path using the original points as starting points and end points in batch from a csv, the point id is it's cat
v.net.path input="pplonpednetclean3" output="dcommute3" type="line,boundary" alayer=1 nlayer=1 file="pplonpednetclean.csv" dmax=1000


#example of the csv
#autonumber,Start node cat, end node cat
1       1       3000
2       5       3000
3       6       3000
4       7       3000
5       8       3000
6       9       3000
7       10      3000
8       14      3000
9       15      3000
10      25      3000
11      26      3000
12      27      3000
#yes all my people traveled to the same end point

Things to watch out for:

  • A network file should have both lines and points with the same layer number(ie 1_points 1_lines)
  • A network file with no cat column in the points component