Quantum GIS: the Open-Source Geographic Information System
Although QGIS contains several essential tools, I briefly discuss only three here: the Pan, Zoom and Identify Features tools.
The most essential tool for navigating around a layer is the Pan tool, the toolbar icon in the shape of a hand. If I click on that tool, I quickly can drag my map around the Map View window.
However, if I want to change the level of detail in the Map View, I must switch to the Zoom tool. Although the Zoom tool is intuitive in function, beware, for it is disappointingly unintuitive in practice for three reasons. First, the Zoom tool resides in the View menu and is not available as a toolbar option. Second, the Zoom In and Zoom Out functions work only using the wheel of a mouse. Because I work on a laptop, I had to acquire a USB mouse just to have zooming capabilities. Third, unlike with most GIS and graphics applications, QGIS does not simply allow one to draw a box around the desired zoom-to area.
Meanwhile, the Identify Features tool is more straightforward and less cumbersome. To activate the tool, I simply press the toolbar icon designated by a mouse arrow next to the letter i in a blue circle. Then, I can navigate to any feature in the Map View window and essentially call up that feature's characteristics—that is, its entry in the attribute table. In order to select the appropriate feature, however, I must select the correct layer in the Legend. For example, if I am searching for information about a lake, I can't be on the Roads layer—the Lakes layer must be selected. Figure 4 shows how I clicked on a large lake and learned its size, elevation and name, Ford Lake.
Now that I've covered the basics of GIS, found the requisite shapefiles, loaded those files into QGIS and explored basic navigation, it's time to find and record locations for my housing project. To find ideal sites where I can restore a wetland on agricultural land close to Ann Arbor, I pan and zoom around my map and toggle layers on and off.
After searching for a time, I decide to save some sites for later reference. The best way to do this is to create my own layer (shapefile). To do this, I click on the New Vector Layer icon in the toolbar, and because all I need are specific locations, I opt for a point-based shapefile. At the same time, I must build an attribute table, which I do by clicking on the Add Attribute button. I need only one string-based field, which I label Locations.
Now that I have my own shapefile, as long as that layer is selected in the Legend, I can add my own points to it by selecting the Toggle Editing tool. Once the tool is selected, the button right next door on the toolbar, the Capture Point tool, is activated, and I can create points anywhere I choose. I create a point for each potential building site I find and add a label to each, as prompted by QGIS. I press the Toggle Editing icon once again to leave edit mode and return to normal browse mode.
Thus far, QGIS has been useful in giving me a broad perspective on natural and man-made features, as well as land-use characteristics. This is much more than what nearly every paper map or Google Earth will give me. Still, QGIS can't do everything. Unfortunately, I probably can't acquire a shapefile with current land-ownership status. Therefore, I must utilize other resources, such as the County Clerk, in order to discover who owns which parcels. Clearly my work has only just begun.
The free and open-source QGIS turns out to be an appropriate tool for projects involving land use, such as my search for a site to restore a wetland and build an eco-friendly housing development. In this project, I was able to locate the geospatial data I needed from a free geospatial data repository, load it into QGIS, tailor the data to my liking and designate a plethora of potential building sites. Besides land-use projects, you also can delve into demographic data, satellite and aerial-photo imagery, other natural and man-made features and more. Although cramming on GIS concepts and conventions was required, working with QGIS and other GIS applications, although a bit challenging at first, is extremely useful, rewarding and fun.
James Gray is Products Editor for Linux Journal
|Dynamic DNS—an Object Lesson in Problem Solving||May 21, 2013|
|Using Salt Stack and Vagrant for Drupal Development||May 20, 2013|
|Making Linux and Android Get Along (It's Not as Hard as It Sounds)||May 16, 2013|
|Drupal Is a Framework: Why Everyone Needs to Understand This||May 15, 2013|
|Home, My Backup Data Center||May 13, 2013|
|Non-Linux FOSS: Seashore||May 10, 2013|
- RSS Feeds
- Dynamic DNS—an Object Lesson in Problem Solving
- Making Linux and Android Get Along (It's Not as Hard as It Sounds)
- Using Salt Stack and Vagrant for Drupal Development
- New Products
- A Topic for Discussion - Open Source Feature-Richness?
- Validate an E-Mail Address with PHP, the Right Way
- Drupal Is a Framework: Why Everyone Needs to Understand This
- What's the tweeting protocol?
- Tech Tip: Really Simple HTTP Server with Python
- Kernel Problem
30 min 30 sec ago
- BASH script to log IPs on public web server
4 hours 57 min ago
8 hours 33 min ago
- Reply to comment | Linux Journal
9 hours 5 min ago
- All the articles you talked
11 hours 29 min ago
- All the articles you talked
11 hours 32 min ago
- All the articles you talked
11 hours 33 min ago
15 hours 58 min ago
- Keeping track of IP address
17 hours 49 min ago
- Roll your own dynamic dns
23 hours 2 min ago
Enter to Win an Adafruit Pi Cobbler Breakout Kit for Raspberry Pi
It's Raspberry Pi month at Linux Journal. Each week in May, Adafruit will be giving away a Pi-related prize to a lucky, randomly drawn LJ reader. Winners will be announced weekly.
Fill out the fields below to enter to win this week's prize-- a Pi Cobbler Breakout Kit for Raspberry Pi.
Congratulations to our winners so far:
- 5-8-13, Pi Starter Pack: Jack Davis
- 5-15-13, Pi Model B 512MB RAM: Patrick Dunn
- 5-21-13, Prototyping Pi Plate Kit: Philip Kirby
- Next winner announced on 5-27-13!
Free Webinar: Hadoop
How to Build an Optimal Hadoop Cluster to Store and Maintain Unlimited Amounts of Data Using Microservers
Realizing the promise of Apache® Hadoop® requires the effective deployment of compute, memory, storage and networking to achieve optimal results. With its flexibility and multitude of options, it is easy to over or under provision the server infrastructure, resulting in poor performance and high TCO. Join us for an in depth, technical discussion with industry experts from leading Hadoop and server companies who will provide insights into the key considerations for designing and deploying an optimal Hadoop cluster.
Some of key questions to be discussed are:
- What is the “typical” Hadoop cluster and what should be installed on the different machine types?
- Why should you consider the typical workload patterns when making your hardware decisions?
- Are all microservers created equal for Hadoop deployments?
- How do I plan for expansion if I require more compute, memory, storage or networking?