Hello,
we have 6 pt / m^2 lidar data covering the entire province of New Brunswick, 72,000 km^2. From the point cloud data we generated a 1 metre bare-earth DEM. We are in the process of creating contour lines from the DEM. So far we have created contours with a 50 metre interval and a 10 metre interval. We are serving this data as a map service. Unfortunately, at small scales it is very easy to exceed the 600 second timeout on the map service. I suspect the problem causing the slow draw times is the density of vertices along our contour lines and the contour labelling. Using a 1 metre DEM as source data for the contours should lead to one vertex for every cell the contour line crosses which would be close to one vertex every metre along the contour. Currently, our stop gap measure is to use a scale threshold so the contours do not draw when zommed out beyond 1:150,000. We are considering eliminating contour labels at smaller scales and producing a "low resolution" version of our contour lines for use at smaller scales. The low resolution contours would have fewer vertices. But I am not sure of the best method to accomplish this.
Have you had to deal with this issue? What did you do to make your contour map service preform better?
Thanks,
Bernie.
