Monthly Archives: August 2009

More Python/ArcGIS Resources…

I’ve scoured the planet and dredged the bottom of the deep web. This is the best I’ve come up with, and it’s actually pretty good. GIS Programming Fundamentals at North Carolina State University. This, together with ESRI’s Writing Geoprocessing Scripts should get the beginners started.

Oh, and I also found this one – two GIS labs from San Francisco State University, Python & Geoprocessing Scripts, and Geoprocessing Scripts with Python.

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Garmin GPS 60CSx

60CSxWell, after reading about a number of more or less highly rated, hand-held GPS units, I’ve opted for and ordered the Garmin GPS 60CSx. I had flirted with the idea of ordering the Delorme Earthmate PN40, but after a number of reviews and visiting expertgps.com I got the sense that the Garmin series might be somewhat more “open source” when it comes to uploading data and interfacing w/other non-Garmin software.

Mapping or not was an easy decision. I want to try to export/upload all kinds of GIS data to the GPS. Ergo mapping. B/w or color was easy, too. This is 2009 ! Over all, Garmin seems to – if not hold an edge over other brands – at least continue a tradition of reliable units. The first GPS I used was a Magellan. This was 1996. I haven’t seen any affordable Magellan units though.

This here was an interesting page about considerations when choosing a handheld GPS unit.

This here – a manual for data collection using the Garmin 76CSx – might come in useful. The only reason I chose the 60CSx over the 76Csx was size. A number of reviewers claimed the 76 was a bit of a clunker. — I will be reporting on how I like my GPS soon.

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Learning arcgisscripting & Geoprocessor Object

Using the Sam’s script was a good lesson in the use of arcscripting and the Geoprocessor Object because I’ve been making slow headway applying my understanding of Python to geoprocessing in ArcGIS. There just seem to be very few (if any) good step-by-step tutorials on this subject. The best thing I’ve found, and I need to get back to and finish it, is a downloadable course (sldeshow) consisting of a number of modules by Geospatial Training (Mastering Python for Geoprocessing in ArcGIS), that attempts to deliver but doesn’t get an A rating from me. Unfortunately, it’s the only thing I’ve found – also somewhat pricey ($99) for a 90 minute course.

The best way still to understand things is, as for any programming, to review existing code and run it, make changes to it and run it again. So checking out Sam’s script, I learned more than from the course.

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Organizing DRG Files

I haven’t solved my programming challenge entirely. But I have gotten half way there. By cheating. – What I mean is I have found help on the web.

After downloading all of Texas USGS topography as DRG, I found a script by Samuel (his awesome blog’s at gissolved.blogspot.com) that searches any starting directory and its subdirectories for geo-referenced raster files, reads their geographic extent, creates a polygon feature of that extent and writes it into a shapefile. When I saw that, I realized that I was half way there. Thanks Sam for the help.
I ran the script once which – parsing through approx. 4500 TIF’s – took some time. When I tried to add the resulting SHP to my map, I realized that the coordinates extracted from the GEOTIFF’s were in UTM. To project and plot the SHP correctly, since Texas is so large that it covers three UTM zones (13,14,15), I had to split the features up.

texasUTM

 

 

 

 

 

 

 

 

 

 

 

Rather than splitting up the SHP, I simply copy/pasted (somewhat laboriously) the TIFF’s into three separate folders and ran the script again. Now, all I had to do is project each SHP in the correct UTM zones using ArcToolBox, and then add all three of them to my map. The neat thing is that each feature has as attribute a reference to the location of the TIFF, so that by clicking on it, you can either open/view the TIFF or see the location where it is stored.

geotiff

Now, I just need to figure out how clicking on that reference or another link/button, I can add that particular TIFF to the map.

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On A Side Note (Python Books at amazon.com…)

amazonas

What exactly do they mean by “Frequently Bought Together” ? How often is that ?

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My Python Library…

In my efforts to teach myself programming in Python, I have acquired a number of books some of which have proved to be more useful to my needs than others. Since it’s a bad habit of mine to always buy one more book than I need, I now own more Python guides than necessary. But maybe some of them will come in handy the day that I am no longer a beginner.

python_abs“Python for Absolute Beginners” was the first title I bought. I read this book while taking an online course, and I enjoyed this introduction. It’s somewhat light and gentle on the uninitiated. It gives you a good idea of why you would want to learn any programming and even manages to make OOP sound fun and useful. Ultimately, this is like a “…for Dummies” guide that will leave you begging for answers to problems outside the book. It’s cheap and a great primer but it won’t take you far.

  zelle I am now reading “Python Programming: An Introduction to Computer Science “. Yes, I am afraid to admit that this has been my bed-time and leisure reading material. I had hesitated to buy this book because it sounded too much like a boring college text book. But it turns out this is the best volume for someone wanting to learn Python and jump start his understanding of computer programming. The book delivers a lot more meat and code examples than the Absolute Beginners book. No, it’s not as funny. But it’s anything but boring. If you’re new to programming and Python (like me), I highly recommend this one. I think there will be much more useful info about algorithms and how to tackle real-life programming problems in this book than in the first one.

lpython

 ppythonI bought both the Mark Lutz classics “Learning Python” and “Programming Python” used on amazon.com. Needless to say that (at 700 pages and 1600 pages respectively) they are comprehensive. And that’s what makes them less useful for the Beginners. “Programming Python” has a great introduction to the language and its ‘structure’ but then quickly drifts off  into areas that I will probably never deal with. “Learning Python” is a great place to look up things – a Python dictionary so to speak. Good to have but not a page-by-page learning tool.

 chunSimilarly comprehensive, leaning towards redundant, is Wesley Chun’s “Core Python Programming”. Again, you can find many language details in this book, but the way the book is organized struck me as an example of how many computer books are bloated with unnecesary chapters and sections just to make them FATTER. This is the only title that was completely useless to me. I admire the effort that goes into books like this one. Maybe it’s a bible to the serious developer. I haven’t touched it in months.

 cookbook Finally, the only O’Reilly title I have found some use for is the “Python Cookbook”, and the reason is very simple: it’s got code, code, and more code. Much of this is in areas I have very little use for. But much of it is very interesting if you’re just trying to figure out how the code works and learn by reading it. This was a worthwhile investment, and I would recommend this much more than others. With this book and Zelle’s intro, I think, any Python beginner would be all set to start coding and learning what Python is all about.

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