Latest Contributions by StormwaterWater_Resources

For the record I received my ArcGIS Online subscription offer on December 23rd and I've since successfully activated it. I suppose I'm still so awed by getting the full blown package along with extensions for ~$100 that I'm not complaining. ... View more

I don't understand that last bit Sorry, I wasn't clear.  When I said "our original contour layer", I was referring to an entirely separate contour layer created by others with unknown source data and before my time.  That is, we had a full county contour layer (2' vs the 1' I was making) which drew at a very reasonable speed.  That was my benchmark in terms of what was going to be acceptable to other users.  I should have said something like: "another contour layer in common use made by others" to make it clear it had nothing to do with my project. Based on what I learned from this thread there was a dramatic performance gain from what I'd originally created.  The resultant layer, still huge and excessively detailed, draws at a perfectly acceptable speed. Thanks to all who posted. PS: For readers new to this thread looking for a quick answer look first to Vangelo's answer in post #4, and then a description of my solution based on this in post #9 ... View more

Fewer rows are faster, except when there's data that can't be rendered. There's the quick and dirty answer to the original question from Vangelo (#4 below). Best practice would be to intersect the contour lines against a regular grid of at least 5x5 over the study area, then dissolve by grid cell and elevation (unioning nearby shapes with the same attribute). Before I tried this I reassembled clipped subsets; I'll describe that in a minute.  However I finally tried the exact method from Vangelo.  Again, my original data set (*un*dissolved) had ~2.6 million features, many with thousands of vertices.  I created a 15x7 grid, and then attempted to intersect the whole thing.  After four days the process finally crashed (out of memory).  I tried these exact steps on a far smaller subset, and it worked perfectly.  The result was that my contours were split up by my grid and dissolved, but otherwise identical to the original contours.  Note: it's the dissolve that really makes the difference in performance. The way that I actually worked with the entire data set was by clipping and then merging.  As far as I can tell this accomplishes the exact same thing.  The entire set of contours was diced up into pieces and dissolved but otherwise identical to the original.  Here are the steps I took: - Create an index grid of squares (Toolbox -> Cartography -> Data Drive Pages -> Grid Index) - Create a model (actually I scripted it, but the model iterator works great too) [INDENT]    - Use Feature Selection iterator over index grid     - Clip the contours with the output of the iterator     - output the new feature class clips into a GDB [/INDENT] - Dissolve the individual clipped feature classes from above [INDENT]   (using another model with a Feature Classes iterator over the GDB)[/INDENT] - Merge the dissolved clips again using a Feature Classes iterator. I suppose this could all be grouped into one model but that's not the way I did it.  I am of course using a scale restriction.  The final product is slower than our original contour layer, but it's certainly acceptable performance. ... View more

Thank you both! I gave the answer to Jake since that solution actually did the selection. I had been thinking that Jake's solution required creating a feature class (or at least a feature) somewhere, but then I realized that this uses an on-the-fly geometry as discussed at the top of the Geometry class help page .  I'd read William's post first, and so researched the extent method. Based on that I tried this: mxd = arcpy.mapping.MapDocument("CURRENT") df  = arcpy.mapping.ListDataFrames(mxd)[0] extent = df.extent grids = arcpy.da.SearchCursor("Clip_Grid",("SHAPE@","PageName")) for grid in grids:     if (extent.contains(grid[0])) or (extent.overlaps(grid[0])) or (extent.within(grid[0])):         print grid[1] And that successfully prints out each PageName value in the equivalent of an intersect.  As a side point, why is there no simple "intersects" method? PS: Oh, there's still the question of whether or not the extent environment parameter for the Select Layer by Attribute tool is actually broken.  Jake?  Based on your logo, can you answer that just for curiosity?  (either way though, thank you for the work-around). ... View more