G'day Sean, On 24/12/2010, at 2:07 AM, Sean wrote:
> Is this just a visualization issue? You could store copies of the the > road line with attribute data indicating direction or have a separate > table with foreign keys to the geography and the direction data. > > Then, you just symbolize differently based on the attributes. Offset > the symbology not the geometry. This is more correct, it preserves > the information about the actual road on which they travel. Showing > direction of travel is strictly a symbology issue. It's a mix of both - initially, it was a geometry issue - I have linestrings for roads, and for some I have information that suggests that they are dual carriageway, and I was wondering if we could approximate the dual carriageway by shifting the original geometry a little bit to the left going each way. Then I realised I had better things to do, so I moved on, but now I have a need to show routes going both ways, but using pgRouting they (unsurprisingly) following the same lines, and I wanted to show it. Using QGIS I offset the symbology, but it doesn't actually seem to works how I wanted (which is nicely described by Simon's post), but rather looks like :
<<inline: Screen shot 2010-12-24 at 9.30.19 AM.png>>
cheers (and Happy Christmas etc) Ben
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