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1822
bio website whatutmzoneamiin.blogspot.com
location Ontario, Canada
age 33
visits member for 3 years, 9 months
seen 16 hours ago

Open source GIS user & advocate.


Jun
25
comment How to create atlas along line/route in QGIS
Are you sure you have "Controlled by Atlas" enabled under the map frame "Item Properties", with a "Margin Around Feature" set (to say 10%)? You should have a page centered on each feature, with the appropriate margin. If you're only getting a small segment (smaller than your 'split' length?) then you've got something set wrong.
Jun
25
comment Qgis making a backgound map for topolines on Garmin
It creates a raster map in .kmz format.
Jun
25
comment How to create atlas along line/route in QGIS
Adam; the Atlas by default will rotate to follow each segment of the "Coverage Layer" -- is it not doing so?
Jun
24
comment How to create atlas along line/route in QGIS
What I would do is "split" your linear layer into a second layer (for using in your atlas only) using v.split.length under Processing (it's a GRASS tool.) Set this as your "Coverage Layer," make it invisible so it doesn't show up on the map, and you're all set. The Atlas pages will then follow the line, rotate appropriately, and overlap based on the 'buffer' you set, which should meet all of your criteria.
Jun
13
comment Split Lines at Intersection of Other Lines
This is bizarre. I just tried the exact same syntax with a single subset (one road, one contour) and it worked exactly as expected. When I run it on the larger database, it doesn't work!
Jun
13
comment Split Lines at Intersection of Other Lines
After viewing the results, it in fact does not appear to work. It simply output my original roads. What am I doing wrong here? SELECT ST_AsText(ST_Split(r.geom, c.geom)) as geom FROM roads r, contour c
Jun
13
comment Split Lines at Intersection of Other Lines
After some more work, I was able to import the data using the DB Manager Plugin, and checked off "Create Single Part Geometries instead of multi-part" and it seems to work!
Jun
13
comment Split Lines at Intersection of Other Lines
Thanks! I am not familiar enough with Python to try your first solution just yet. The OpenJump solution somewhat works, but leaves all of the data in one layer, with no attributes present to separate them back out into the original layers. Any thoughts on how to do this?
Jun
13
comment Split Lines at Intersection of Other Lines
Thanks! I was able to mess around with this a bit, and found it didn't quite work. I had the error "Splitting a Line by a MultiLineString is unsupported." After some further research, it seems that ST_LineMerge may solve the problem, so I tried: 'SELECT ST_Split(r.geometry, c.geometry) FROM (SELECT ST_LineMerge(geom) from contour AS linemergec) c, (SELECT ST_LineMerge(geom) from roads AS linemerger) r' - but now I'm getting the error: "cannot cast type record to topogeometry ^ DETAIL: Cannot cast type geometry to integer in column 1"
Jun
13
comment Is it possible to create Rule-Based Styling with $geometry intersecting a second layer?
Thanks underdark; at least I wasn't missing something! I figured perhaps it was not possible.
Jun
6
comment Is it possible to create Rule-Based Styling with $geometry intersecting a second layer?
The second layer is a polygon shapefile that has been added to the QGIS project.
May
29
comment Split Lines at Intersection of Other Lines
gene; as per my above comment, the Union in OpenJump is not working as expected (in fact it is doing nothing.) I also noticed that there are multiple Union commands (which is bizarre). Can you walk me through that step? How is Tools>Analysis>Union/Dissolve/Merge command different than Tools>Geometry Functions>Union (Function)? Neither of these seem to make sense based on any "Union" command I have used in other software.
May
28
comment Split Lines at Intersection of Other Lines
gene; can you walk me through this? I can't actually seem to perform a Union of the two line layers in OpenJump either--it just does nothing, presumably because it is also expecting a polygon layer as one of the inputs.
May
27
comment Split Lines at Intersection of Other Lines
Care to expand on that with a possible solution?
May
27
comment Split Lines at Intersection of Other Lines
gene; unfortunately, v.overlay is expecting an area for one fo the layers as well. As per the manual: "v.overlay allows the user to overlay two vector maps. Features in ainput can be lines or areas and are cut with areas in binput."
Apr
15
comment How can I create/draw “freehand” polygon features in QGIS 2.2?
What OS are you running? How did you install QGIS 2.2? I just tried on my Windows7 system, with QGIS2.2 installed via OSGEO4W and it worked fine. Are you sure you have a polygon or line layer, and that it's editable?
Mar
20
comment How to avoid snapping errors in QGis?
I rarely use the snapping settings in meters--I find that pixels makes more sense. If you measure your small differences, are they less than 1.5 meters, or greater?
Mar
6
comment How to determine if an object is a circle
Thanks; you're right, and that makes sense! I guess the difference was how many digits of pi used - I only used a couple digits!
Feb
28
comment Is there a consumer-level handheld GPS that can use standard GIS data as its background layer?
Agreed; if you can figure out the battery concern, that tethering a 'real' GPS to a smartphone is likely the best option.
Feb
27
comment Show the paths but not roadsides and driveways in the line layer
Are there only paths in the nature areas? If so, you could clip the line layer with the polygon woodland area layer.