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In my previous post, I showed how to prepare the data for a bivariate choropleth map using PostGIS and QGIS. I also indicated that there is a website that shows an ArcGIS tool to do it. But, this actually turns …
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A friend recently asked me about the cool looking bivariate maps produced with ArcOnline, lamenting that the capability seemed lacking in ArcGIS. Well, it turns out that ESRI has a .dll you can use, and there is a good article …
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gisadvising by Art Lembo - 4M ago

I just got off the phone with a very large developer. I want to call him a GIS developer, but really that’s not was he does. Rather, he is a spatial solutions developer. According to him, when we talk about …
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A friend is doing some research on estrogen and estrodial in water samples in Delaware. We have about 50 sub-watersheds that show the upstream contributing area for each water sample. We’ve done some regression analysis to see if we can …
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As promised, let’s walk through the code I wrote to create the multiprocessing of my Postgres/PostGIS task.  You may recall that I said that it only took 4 lines of code – well, sort of.  The parallel processing was really that …
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OK, let’s cut to the chase: I used Python’s parallel processing capabilities with Postgres to perform a spatial overlay on approximately 25 million taxi pickup locations (over 5 GB of data), and processed all of it in under 3 minutes!!  …
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We just completed another two successful Keeping Up with GIS Technology workshops out in Denver.  This was a week mixed with sadness and joy: sadness in that my Mom passed away on Tuesday, and I had to fly out of …
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Just a quick follow-up to my big data test.  If you remember, I was able to determine the number of taxi pickups and the sum of the fares for each zone using Postgres and PostGIS in 1m 40s.  Some of …
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gisadvising by Art Lembo - 9M ago

I wanted to revisit the taxi data example that I previously blogged about.  I had a 6GB file of 16 million taxi pickup locations and 260 taxi zones.  I wanted to determine the number of pickups in each zone, along …
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