[Geomoose-users] Are Polys or lines faster

[Jim Klassen]

I think for an official answer you would have to ask the mapserver list.

My guess would be that lines (not polylines) could be faster if your polygons are typically a lot larger than the users view because Mapserver would need to look at the whole polygon compared to a few line segments. However, there could also be a trade off with the number of features it has to deal with. If I remember right, and it has been awhile since I looked, the inner loop of the Mapserver code loops over points (for points, lines, polygons alike) so reducing the number of points that it has to look at for a given request would likely be the way to speed things up.

My guess is the usual tricks such as using .qix files and, if the polygons are complex, having a generalized set of polygons for when the users are zoomed out would make a bigger difference.

Also keep in mind that if you are using popups or the identify tool in GeoMOOSE, lines and polygons act differently (there is no inside a set of lines). You can render a polygon as a outline with no fill, which would visually look like a line layer.

>>> "Jim Dahl" <jim.dahl at mail.co.douglas.mn.us> 11/26/08 8:54 AM >>>
Hi all, which is faster to render, polygons or lines.  I have a water
layer with about 19,000 polygons and intend on showing them as line
features instead of polygons.  Would it be faster to convert them to
line shapefiles or leave them as polygon shape files.  I can try my test
and report back but wanted an official opinion from the group also.
 
Thanks alot.
 

Jim Dahl, GISP
GIS Coordinator
Douglas County Public Works
509 3rd Ave W
PO Box 398
Alexandria MN 56308

V 320-762-2933
   320-763-6001
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