Here are some comments about the second part (which is more a user issue).
draw speeds of about 30 seconds I was impressed that QGIS could handle
such a large dataset. Any comments?
You might gain speed gains doing some or part of the following:
- put your dataset in a database (suggested: postgis or spatialite)
- simplify your dataset for visualisation at small (overview) scale; try to
draw non-simplified data only at detailed (large) scale
- if you insist on shapefiles, make sure you created the spatial index (there
is one button in QGIS for this)
- probably it does not make sense to display all the data at all scale.
Depending on semantic needs, optimisation is possible here. In addition,
polygons with a very small area can easily be ignored at small scale (they
would probably be displayed with a single pixel anyway): pre-compute the scale
of each polygon, and create a scale based rule in rule based renderer. (or use
a query at the layer level).
When you say contour polygon do you mean level curves (elevation data)
[hence: might be linestring, not polygons]? Then at small scale you could show
only main level curves (every 100 m).
Doing this I can browse the Openstreetmap dataset + level curves/contour for a
European country (1Gb of data) with a rendering time of less than 1 second.
If you have several layers, you may want to try and build the threading branch
for even faster rendering (multicore).
Mayeul
- Mail Original -
De: Bob Bruce (CON) bob.br...@gov.mb.ca
À: qgis-developer@lists.osgeo.org qgis-developer@lists.osgeo.org
Envoyé: Jeudi 17 Mars 2011 16h53:25 GMT +01:00 Amsterdam / Berlin / Berne /
Rome / Stockholm / Vienne
Objet: [Qgis-developer] Status of Release 1.7 and Raster-on-the-Fly
I am preparing to do a presentation on QGIS to a GIS users group meeting in
Brandon on Friday. What can I say about when 1.7 will come out? Will it have
the Raster-on-the-Fly capability that is being tested at the moment?
I have been doing some testing with a polygon file of contours have 54614
polygons and it is 770 Mb in size and an getting draw speeds of about 30
seconds on my DELL T3500 system running Windows 7 with 4 Gb of RAM. The contour
polygons are at 5m intervals. (I have some screen captures of some of the draws
if people want to email me directly for them) This seems like a pretty fast
response time and I was impressed that QGIS could handle such a large dataset.
Any comments?
Bob Bruce
**Bob Bruce, FEC, P.Eng. Geomatics Support Engineer
**bbr...@gov.mb.ca Manitoba Lands and Geomatics
Branch,
**work # (204) 945-66361007 Century Street,
**FAX # (204) 945-1365Winnipeg, Manitoba, Canada, R3H
0W4
**
**The Manitoba Centre for:
** Cadastral Topographical Mapping, and Remote Sensing
** See us on the Web at:
http://www.gov.mb.ca/conservation/geomatics/
** and:
http://www.gov.mb.ca/conservation/geomatics/cada_mapping/index.html
** Check out our digital maps at: http://mli2.gov.mb.ca/
** and WMS: http://mlidata.gov.mb.ca/wms/request.aspx
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