Did you know that QGIS can design graphical models, similar to the way Model Builder in ArcGIS works? The following video is taken from...

Technical and Detailed. Great teacher explanation. Really good! Practical advice, in-depth enough to really learn something useful (most...

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...

A friend recently asked me about the cool looking bivariate maps produced with ArcOnline, lamenting that the capability seemed lacking...

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...

A friend is doing some research on estrogen and estrodial in water samples in Delaware. We have about 50 sub-watersheds that show the...

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...

NYC taxi cab pickup locations for October, 2012 OK, let’s cut to the chase: I used Python’s parallel processing capabilities with...

two successful Keeping Up with GIS Technology workshops out in Denver.  This was a week mixed with sadness and joy: sadness in that my...

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...

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...

We had a very successful workshop on GIS at the Maryland Geospatial Conference – well, actually two workshops.  I was asked to teach a...

Recently, we were asked by our new University President, Chuck Wight, how our students are doing in obtaining their first job.  You have...

Do you have a set of lines that you need to determine if there are any “dangle” nodes?  A dangle is a line segment that overhangs another...

In my last post, I showed you how to create multi-ring, non-overlapping buffers with spatial SQL in PostGIS.  In this post, I want to do...

I was interested in creating mult-ring buffers but with a twist: I didn’t want the buffers to overlap one another.  In other words, if I...

Sure you can solve it with a few for loops,  inserting the results into a new table, but that really is a hassle.  Also, I have to do it...

Lots of people ask me how to get data into Postgis.  This video is a quick 9 minute demonstration of 3 ways to get data into Postgres...

I telling the guys at Manifold when something isn’t working the way I think it should.  On one hand, I get the satisfaction of sticking...

(yes, I meant to say Beast).  Today I began to experiment with processing some large raster DEMs, and making contours.  I used ArcGIS,...