using QGIS 2.2 and trying to figure out a way to obtain a distance measure for the width of pavement. I have 2 shapefiles: one of points which are at 5m intervals along the pavement centreline and the second is the polyline of the pavement. I'd like to take a distance measure from the point to both edges of the pavement, thus giving me the width. The real challenge is to get a width measurement that is the least angular change and the maximum distance - this is in order to deal with curved and wide pavements as seen in the graphic. Advice will be most welcome - unfortunately, I can't code which is quite a limitation when trying to get to this solution.

Many thanks, Khan

pavement as polyline and centreline of pavement as points

  • How did you acquire the points at the 5 meter intervals? Because your description of them being at the 'centreline' of the pavement doesn't seem to match the image above (i.e. the two points in the indents to the right). – Tim Couwelier May 15 '14 at 15:35
  • That said, to get accurate measurement, you'd need to create a smooth curveline through the points (or just 'connect the dots' which you then smooth with the generaliser plugin), figure out a way to draw perpendicular lines on that curved line through the points, intersect those perpendicular lines with your pavement (which ideally would be a polygon layer rather then lines), and then you end up with straight line segments perpendicular to the 'walking line'. This is a decent approximation of the width. – Tim Couwelier May 15 '14 at 15:37
  • And the above reasoning was set as comment rather then answer, as the bit where you generate the perpendicular lines has me stumped for now. – Tim Couwelier May 15 '14 at 15:38
  • Hi Tim, thanks for the response. At this stage it is experimental, nevertheless, I went through a process of having to reclassify the data in order to use ArcScan in ArcGIS in order to create the centreline using 'Construct Points' function at intervals along the created centreline. The 5m intervals btw are due a legal requirement. – user26001 May 15 '14 at 16:07
  • ArcGIS has a Generate Near Table which is great if one has won the GIS lottery and upgrade to ArcInfo.! ho hum... resources.arcgis.com/en/help/main/10.2/index.html#//… – user26001 May 15 '14 at 16:09

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