Geoprocessing with Python

This week was a little less stressful than last week.  Having used geoprocessing tools in ArcMap, I think I had a more clear understanding of what I needed to accomplish my task.  This week we needed to create XY coordinates from an existing point feature class.  Next we needed to create a 1000 meter buffer around the points, and then dissolve that buffer.  Our script needed to print all messages from each of the geoprocessing steps.  These are the result messages as they appear when using Python in ArcMap .

Script results

I must admit, I always get a little nervous when I see someone else has taken a different route to get the desired results.  I have flashbacks to six grade algebra and the nuns at Catholic school yelling "You have to show your work!"

Python Fundamentals Part 2

What the holy hell happened!  Man o man, did I hit a wall this week.  The first few week of this course and I'm zipping through it thinking this is going to be a great summer and then week 4 happened.  I realize, that I am a visual learner.  I need to see the action in order for it to click in my head, I need to be able to dissect the working code in order to understand the ins and outs.

This week, we were given the start of a script.  The import random module was already loaded at the start of the script.  We then needed to find some errors in a block of code that would allow the scipt to run properly. Luckily, the lecture helped to clear this up.  And then step three happened.  In step three we were to create a list from scratch using 20 random numbers between 0 and 10.  I knew some of the modules that I needed to use, and individually I could run them with proper results, however, the while loop, threw me.  I had a very hard time comprehending how to include the append function and the random integer. Once I got past step 3, things seemed to move along a little better.  Once I had my list created, I needed to create a random unlucky number that would be counted and then removed from the list.  I'm not sure why this while loop was easier to understand than the last one, perhaps because I was able to dissect the previous one.  Our final results were to include the original block of code that we fixed, our created list, a statement declaring how many of the unlucky number would be removed from our list; if any, and our final list with the unlucky number removed. Below are the result of the my script.

Script results

Here's hoping my clicker works better next week.

Mapping the Herrin Massacre Potter's Field

The Herrin Massacre took place in Williamson County Illinois in 1922.  A chance meeting between a historian looking for the gravesite of a WWI vet killed in the massacre and a geospatial scientist initiated the mapping of the Herrin Massacre Potter’s Field and the entire Herrin City cemetery.   The project took approximately four years to complete, mostly because of researching the data that was not previously digitally recorded or was missing completely.  Data was input into a sql database and a custom enterprise geodatabase was created and shared through use of various services via ArcGIS for Server.  

A GIS model was created from an old hand drawn map using known dimensions.  This model was used as a template since it was just the conceptual drawing.  Using data created and recorded over the history of the cemetery, the team was able to map the routine of each of the sextons over the years to approximate the location of the potter’s field. 

Detailed typography, headstone outlines, and satellite imagery were processed in ArcGIS 3D Analyst.  This gave the team the ability to locate unmarked sites by analyzing the subtle changes in the ground surface. 

Though these combined processes, the team was able to sumise the lot in which the potter’s field was potentially located.  Their continued research and proven geographical, historical, and geospatial data was enough evidence to convince the city to allow excavation.  On Nov 12, 2013 the first vault and coffin were discovered and confirmed based on historical accounts describing the coffins and photos taken prior to burial.

What I found most interesting about this article was the use of new age technology to bring back the past.  Even though the records were missing, the team was able to analyze the available data to correctly locate burial sites that lay unnoticed for nearly 90 years.  Being able to analyze subtle difference in ground depression to find the unmarked graves could not have been accomplished using just satellite imagery or aerial photography.

http://www.esri.com/esri-news/arcuser/spring-2014/finding-the-victims-of-the-herrin-massacre

Herrin Massacre Information

Python Fundamentals Part I

This week we started compiling basic Python code. The key to understanding code is to understand the psuedocode.  For example, where do you start, what are the steps in the middle, and what should the end result be.  For our lab, the psuedocode would look like this:

1. Create a string for your name
2. Split that string into a list
3. Print last name
4. Find the length of the last name
5. Multiple the length of the last name by 3
6. Print length of last name times 3

This took some trial and error. As I was going along in my script, I would use the print command after each line of code to ensure that I was getting the correct response.  It took a while to wrap my head around the concept of creating the variable lastNameLen.  I had to realize that I had to tell the code what the variable lastNameLen would be equal to the last list item of my last name.  Once it clicked, the rest of the script seemed to fall into place.

The image below is the results of my script. You can see that my last name Williams is printed (step 3) and so is the number 24, which is the multiple of 8 (the number of letters in Williams) x 3.

Script Result