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I did extensive testing this morning and I think I hit upon the issue. A strong possibility for the lag time is that exercises 1a and 1b uses definition queries for the LA river and city outline (from much larger files). Thus, I assume, the query may have to be done each time one zooms, pans, etc.?? I exported the LA river and city outline queries into shapefiles, added to the map document and then deleted the old layers (with definition queries). MUCH FASTER. Nothing over 7 seconds. I redid the test with the layers (again without definition queries) as geodatabase feature classes (but not inside the feature datasets�??thus, still GCS_WGS_1984). Same result�??FAST. Thus, no difference between shapefile vs. feature class. Thus, to me, this clearly suggests that the definition query is slowing things down considerable, and, secondary�??the reprojection on the fly. Thus, my suggestion of users of your book would be that they export their definition queries into new shapefiles/feature classes, thus avoiding this potential issue. However, you should note that even after doing this occasionally the basemap layer would not display (although it is in the table of contents). Re-adding the basemap layer or restarting ArcMap and then re-opening map document fixes this issue (this only happened once to me after exporting the layers�??and ridding my map document of the definition queries). ArcGIS version: ArcInfo Desktop 10.0 service pack 4.
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06-07-2012
07:46 AM
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I'm considering using the Understanding GIS: An ArcGIS Project Workbook for my undergraduate GIS class. I'm an experienced ArcGIS user, having taught undergraduate GIS classes for over 15 years. I've spent most of today (6/4/2012) testing some of the exercises (mostly chapter 1). I've tested on 3 PCs (2 windows 7, 1 vista)--two have very fast internet (I did a speed test) and the other is my home PC (moderate internet speed). I'm getting extremely slow response/refresh times when I use the ESRI map services with the tutorial data. My slowest was a 9 and 1/2 minute load time for exercise 1a (end of exercise). Panning across the page the refresh of the imagery layer and the L.A. river/L.A. boundary would take from 4 seconds to over 2 minutes (most of the time 15-25 seconds). Twenty-five seconds is an eternity for a student! I'm really concerned this book has a potential fatal flaw--it's dependence on ESRI streamed map services. I've taught Web GIS--so I'm up to speed on how map services work, projection on the fly, hardware acceleration, etc. If I turn off the tutorial data (which I believe are in WGS84, then the Web Mercator basemap(s) certainly run much faster. I like the book and it's advanced introductory level (perfect for one of my classes). It's well written and I like the project approach. But the bottom line is that my students need to have reasonable response times when working with the tutorials. Patience is not a virtue of today's average undergraduate student! Does anyone have any insight on this issue? Were the ESRI map servers slow today (6/4)? I've got to make a decision in a few days. Any suggestions? Dave
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06-04-2012
03:19 PM
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