How to use a free open-source GIS for i-Tree work

Have you created a work-around to a problem you faced with i-Tree? Or have you built a usable tool, template, or guide that you think others might find useful? Use this forum to share your i-Tree tips & tricks.

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How to use a free open-source GIS for i-Tree work

Post by Jerry » Sun Aug 02, 2009 4:11 pm

Interested in doing some of the GIS work for i-Tree but don't happen to have $8,000-$12,000 for software? Then this tip is for you.

There is an excellent free open-source GIS package that works on Windows, Mac and Linux named QGIS that handles the main actions for Streets and Eco without problem. Here are the steps to set it up:

Go to the QGIS downloads page, go forward a couple of pages to where version 1.1.0 is listed (see attached graphic) and download the package for your platform. This is labeled "unstable software" but I have never had any problem with it on either Windows or Linux, and it is so much better than its predecessor that it is definitely the way to go. (For those not used to open-source software, I should mention that this package is of no threat to your system.) I have no experience with the Mac system here, so will not mention it again--hopefully, someone will that add that installation information to this tip.

Windows users will probably want to use the version "Windows-OSGEO" unless they have a very slow connection. This version should bring all dependencies.

Linux users should choose the one for their distribution--I used the Debian Lenny package which can be installed right through the repositories once the QGIS repository has been added as described on that download page. Linux users may well have to install the package python-qgis or python-qgis-common to get the plugins described below to work. Different distributions have somewhat different installation methods, check your forums for details--and don't forget the QGIS forum.

NOTE: the following is only for versions prior to 1.4. In current versions, ftools is included in the basic installation and shows up under the menu item "Vector"
Once you have the basic package installed, you will want to be able to install the plugin called ftools. To do this, click Plugins on the menu bar of QGIS, then Plugin Manager. Click to Get list, then find and check the box to install the Plugin Installer and say OK. Close and reopen QGIS.

Now click Plugins --> Fetch Python Plugins, then click on the Repositories tab and on the Add 3rd party plugins button. Now return to the Plugins tab, highlight ftools that you will now see on the list, and click Install plugin.

This will install a new menu entry "ftools." If you explore it, you will see both Clip (used to cut a section out of the roads raster file for Streets) and Random Points (used to drop locations inside a polygon for Eco).

Very simple to operate: open the two files you are going to use, fire up ftools, fill in the blanks, and you are good to go. You can use the QGIS select tool to cut a single community's polygon from the TIGER/Line file, then right-click the file name in the Table of Contents and select Save selection as shape file.

Enjoy--and save your money for something else!
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Last edited by Jerry on Thu Aug 05, 2010 8:22 pm, edited 3 times in total.
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Post by Jerry » Mon Aug 10, 2009 11:33 am

(Man, this forum's awfully quiet!)

Did anybody try this out? Any installs on Mac OS?

Posts: 100
Joined: Wed Nov 28, 2007 8:11 pm

Post by Jerry » Sat Feb 13, 2010 1:46 pm

(Almost 1,000 views and not a single comment...) I have corrected the outdated download link to direct the user to the right location.

If the i-Tree Team ever decided to support this option, the nice thing about open-source software is that the stable packages could be cached on i-Tree servers for easy download and installation.
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Post by rfswanson » Mon Mar 08, 2010 12:39 pm

I'm using QGIS 1.4.0 Enceladus and it's working very well for the iTree applications; however it has a very limited "Select by Location" feature. I cannot select the Tiger road segments that are completely contained inside the area of interest (the town where we will be sampling) so I have resorted to clipping the road line segments within the town boundary. Do you think that this will corrupt the street segments? Do you have any suggestions of what to do otherwise? Thanks for your time and for turning us onto QGIS, it has been a big help!
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Post by Jerry » Mon Mar 08, 2010 2:30 pm

I'm glad somebody tried it and found it useful!

I am no expert and usually klutz around when I run into such problems--I think I tried Ctrl-click to manually exclude/include segments once in a situation like you are decribing, but I don't exactly remember since it has been a while.

Support for QGIS is through the forum:, and I highly recommend you register and post your question there--those people actually know what they are talking about...

Good luck.
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easier install method

Post by Jerry » Wed Jun 02, 2010 1:50 pm

For anyone who is interested in using QGIS on Windows, I have come across an easier method. This is a netinstall setup, meaning that you must have a working internet connection before you start. Here are the steps:
  • Download the OSGeo4W Installer.
  • Run the installer.
  • Select Express Install, and Next.
  • Pick QGIS to install, and Next.
The selected packages and their required subpackages will be downloaded and installed automatically. Not running Windows myself, I didn't test this, but many commenters say it is foolproof.


EDIT: Tried this on my old laptop to install the new QGIS 1.5 for Windows and it worked well.
Last edited by Jerry on Mon Aug 02, 2010 2:25 pm, edited 1 time in total.
Posts: 100
Joined: Wed Nov 28, 2007 8:11 pm

Beating this horse...

Post by Jerry » Fri Jul 30, 2010 7:04 am

There is an excellent introduction to GIS using Quantum GIS available:

A Gentle introduction to GIS

Might be pretty handy for anyone considering a low-cost i-Tree workshop on this technical topic.
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