If you've worked with ARC/INFO (or any GIS really), you often have to make a determination about the coordinate system of your data: if you want to reproject the data into another coordinate system, you use PROJECT , but if you want to simply overwrite the coordinate system of a layer, you would use DEFINE PROJECTION . PostGIS allows you to do both commands rather easily. So today, I'll show you both of them. I often find that I need to do these commands a lot, especially

Rather than starting with the easiest or hardest function, I thought I'd start somewhere in the middle - for GIS experts I don't want to bore you, and for novices, I don't want to blow you away with something more complex. But, after this post, we'll work through some easy queries and move on to more advanced queries. For those of you who used ARC/INFO, you probably found that the NEAR function was one of your best friends.  I used it every week to transfer attributes from

Two of my favorite things: my trusty ARC/INFO mug from 1990, and my trusty dog Pepper, painted in the style of Andrew Wyeth's Homer . At the recent FOSS4gNA conference , I had the pleasure of hearing about some of the new features in PostGIS. One such set of features were the Coverage related features ( ST_CoverageInvalidEdges , ST_CoverageUnion , ST_CoverageSimplif y ). These functions made certain adjustments in the data structure to allow for faster spatial operations. L

If you are like me, you love writing spatial SQL. But what can you do if you have a geodatabase, some shapefiles, or any other data...

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

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...

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...

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...

In my last video, I gave a short of mile-high view of how SQL can be used for big data geoanalytics.  I want to dive a little deeper, and...

I’m getting ready to create a course in big data analytics with GIS.  I have lots of ideas as to what to do, but one thing I know is that...

The TuGIS training workshop on March 20, 2017 is completed – you can see the workshop evaluations below: The workshop evaluations are in...

GIS Programming students presented their programming projects to ESRI. First, I cannot say enough to thank ESRI for taking time out of...

I’ve always been proud of our Salisbury University GIS students, and love to push them as far as their little minds can handle it.  You...

UMD provided me with enrollment numbers, and we are getting a pretty full class.  However, a few people on the “outside” have asked for a...

Well, even though you didn’t ask for it, I decided to create a k-nearest neighbor analysis in PostGRES/PostGIS.  This has lots of...

I wanted to give you another look at some features that Radian Studio will offer. I’ve shown how we can use SQL to replicate the ARC/INFO...

How I used SQL to generate an accumulated sum of spatial data My friend Tomas does work with business analytics, and wanted to find a way...

A friend recently asked me to help him generate polyline shapefiles with Z and M values that he could deliver to a customer.  The problem...

As most of you know, I am a big fan of spatial SQL.  It is my go-to tool whenever working with GIS.  But, I have seen too many people...