We'll continue our look into ESRI commands in PostGIS by examining another simple task: calculating the Mean Center of a data set. To illustrate these concepts, I will be showing examples from my book Statistical Problem Solving in Geography .  In my textbook, I have an example of 7 data points: So, we can recreate the same results with the following SQL: this query gets the average X and Y coordinate values for a point layer by first converting the geometry into X and Y val

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

I just started experimenting with a free and open source Web GIS framework called MapStore. MapStore is developed by GeoSolutions, and...

I've blogged about how enjoyable my job has been to teach in our Master of GIScience Management at Salisbury University. I love the...

In my previous post I showed how easy it was to stand up a Manifold Server application using an old laptop with 8GB of RAM, and my cable...

I wanted to revisit my post from a couple of weeks ago on parallel processing using a desktop computer. As I began introducing these...

In a previous post, I showed the new Internet mapping API from Manifold GIS that allows users to deploy their GIS data on the Internet...

In my previous blog post we looked at parallel processing using a number of desktop GIS products using a relatively large dataset of...

Did you know that you can perform GIS analysis using parallel processing on a desktop PC? For years now, computers have had multicore...

This semester was quite busy, as I oversaw 9 Master's projects in our MS in Geographic Information Science Management program (MSGISM). ...

This semester was quite busy, as I oversaw 9 Master's projects in our MS in Geographic Information Science Management program (MSGISM). ...

I had a great semester working with my students using desktop, server, and developer tools with Free and Open Source Software for...

In my previous post, I showed how my GIS students were able to adapt to QGIS as a desktop GIS, and also the model building capabilities...

In my last post, I showed that my lower level undergraduate students were performing quite well in their online transition, when learning...

We're now about 6 weeks into our experiment of transitioning our University instruction to an online environment. Because we...

I just started working with the Time Manager plug-in with QGIS to create an animation of recent COVID-19 deaths in Maryland: The map...

Due to the COVID-19 virus, many of our schools are struggling to turn their courses into online delivery. I just found out that our...

Due to the COVID-19 virus, many of our schools are struggling to turn their courses into online delivery. I too am getting my courses...