Thursday, February 27, 2014

QGIS 2.0 Dufour on a Nexus 7 Tablet

An update for readers of last year's post about QGIS on a Nexus 7 tablet/slate.  In this post, I will  cover downloading, installing, and using QGIS on a Nexus 7 Tablet (1st Generation, 8 GB) running Android 4.4.2 KitKat.  This is the same tablet I used last year.  Keep in mind this tablet's touchscreen is only 7 inches.  Larger tablets are on their way, with a 12" Samsung tablet already available.

You will also gain an understanding of what additional apps you will need to make the experience as smooth as possible.  Lastly, I'll discuss the strengths and weaknesses of QGIS on this particular tablet.

QGIS on Android is a work in progress.  Since many people may try installing QGIS for Android on their own tablet, a friend's, or even a work device, proceed at your own risk. To date: I have not had any problems with installing QGIS on my tablet.

Downloading, Pre-Install, and Installation
  • Before installing QGIS, make sure your device has enough space for installation (~600 MB) and downloading at least a few GIS-related shapefiles or rasters.  On mobile devices, storage can run out really fast.
  • Head over to the QGIS for Android page and select the "Download" link, then click the link for QGIS installer at the top of the page to download the *.apk or Android Application Package.
  • You will also have to download Ministro which is available on Google Play.
To make your QGIS experience even better also download a file explorer app, such as File Manager, and a de/compression app like EasyRar or ZArchiver --since GIS files are really a set of files that work together. Clicking on the screenshots below will enlarge them.

A screenshot of an unpacked shapefile in File Manager
After downloading the APK, head to your download folder and follow the onscreen instructions.  Installation will take a few minutes.  QGIS will appear as a little green android icon with a Q on its stomach.  After starting QGIS, you will be greeted with the familiar loading screen and tips.

Using QGIS
When using QGIS on a tablet, you may want to consider un-checking the "render" button until you are ready for your map to be displayed.  You will  also notice a "canvas rendering" progress bar while maps are rendering.

For this post, I visited the National Atlas page in my tablet's Chrome browser and downloaded several tar files.  Next, I navigated to my "Download" folder on my device, extracted then to a new folder, and then unpacked the contents.

A Single Vector Layer
Even on a small tablet,you can see a lot of real estate...

 Unemployment Rate 2009, by County
Raster and Vector Data
Like a desktop GIS and QGIS on desktop, you can begin to create eye catching and more complex map products--with multiple layers, data types, and labels.
Hawaii, cities, volcanoes, and risk of lava flows, transparent, overlaying imagery. 
Metadata, important regardless of where you do your GIS work, can be viewed using several different programs, below using Android's text editor:

Saving a Map
One esoteric step is when you go to save a map or *.qgs file.  You will have to add the file extension ".qgs" to your filename to be able to successfully save your map. Otherwise, the "save" button will not be available.  (I am currently looking through the bug listings to see if this is already a known issue.)

Good with improvements over earlier versions.  Overall, installing, importing data, symbolizing it, and other basic features of QGIS 2.0 are easy to implement on a small seven inch tablet.

However, you will need patience working on a seven inch screen and there are limitations.  For example, some slide bars for large drop down menus were too thin to select, even with a stylus.  Reordering layers was almost impossible using this small touchscreen.  The map composer was also too difficult to use and did not display well.  Crashes are rare and generally occur when the user performs several different actions very close together in time or sequence.  Performance will vary depending on the device you use.

Newer tablets have increased processing power, memory, and storage--all of which should help performance.  Given the rapid rise of mobile, having a free desktop GIS on tablet so soon is a big achievement!  Later this year, I plan to get a larger tablet--which should improve the ease of use with QGIS. I will be sure to install QGIS for Android and give it another go!

Thursday, February 13, 2014

A Second Free Look at the Luxor Hotel...with LAStools

I took a second look at the Luxor Hotel but this time with LAStools in QGIS.  If you missed the first post, check it out here:

Before I go a step further, it is important to note how to install LAStools into the processing toolbox of QGIS.  Essentially there are two parts: 1) adding a new "Lidar" folder to the QGIS program folder and 2) activating and linking LAStools to QGIS. Avoid placing this folder in any directory with a name that has spaces in its name, for example \My Documents\.

After that, it should be smooth sailing!  It is a really powerful toolbox that integrates well into QGIS.  There is also an ArcGIS toolbox too.

LAStools comes with a lot of different features for viewing and understanding lidar data.  Just a few of them are implemented below. Click on any of the images to magnify them.

                         Using lasclassify...
The same lidar data classified into different categories using lasclassify--and triangulated.

                       Using las2dem and las2iso...
Contours overlaying a raster DEM using las2dem and las2iso.
                         Up close - an impressive view:
The details of the sphinx, including head, front and rear legs, can be easily distinguished.

Tuesday, February 4, 2014

CrimeStat IV Released...Not Just for Crime Analysis...

CrimeStat IV was recently released, but you do not need to be a crime analyst to appreciate it or find it useful. CrimeStat is a lightweight piece of freeware with heavyweight analytical capabilities. 

Last year, I used CrimeStat to show different programs performing basic density analysis.  But, CrimeStat can really do a whole lot more!  CrimeStat IV boosts 60 different routines, so there is plenty of analytic power in this Windows-based program.

An abbreviated list of features:
  • Importing two files with X/Y coordinates
  • Creating a reference grid
  • Using different types of distance measurement
  • Measures of Spatial Distribution (Mean center, standard distance,etc.)
  • Spatial Autocorrelation Indices
  • Distance Analysis (Nearest neighbor, Ripley's K,...)
  • Hot spot analysis 
  • Spatial Modeling/Interpolation
  • Journey-to-crime analysis
  • Spatial Modeling (several types of regression models)
  • Time-series forecasting
First, CrimeStat is not a GIS.  For example, you cannot view, create, or edit spatial data or visualize any maps/GIS-related files within it.  Rather, it is a program that imports, conducts spatial analysis, and exports results for being imported into any GIS.

On the other hand, you can import GIS-related file types such as shapefiles, *.dbf files, and ASCII/delimited files (i.e. *.csv).  Once you have decided on what type of analysis you are going to run, be sure to read how to import your data.  Once past this minor obstacle, you will be free to conduct your analysis...for free!

CrimeStat's tabs make navigation easy.  The program opens to the Data Setup tab--which is a necessary first stop. Click to magnify the screenshot below.
Like many free and open source programs, learning on how to import your data is a crucial first step!  Understanding your projection, as always is also key, especially when moving the results back into a GIS.
The Spatial Description analysis tab shows the basic premise of CrimeStat.  After loading your data, the program makes the necessary computations and 'saves result to'/Saves output to a folder for importing into a GIS.
Since this is version 4.0, CrimeStat's documentation is well organized by type of analysis.  The website contains plenty of exercises and sample data to minimize.  I was a bit disappointed that a Quick Guide is actually more like previous' versions workbooks--and exceeds 200 pages.  I would recommend starting at Chapter 1 and reading each of the first few chapters on it own.  You can then move on to specific analytic chapters--as needed.  Still, all the documentation is in order. Lastly, you will find real world case studies by leading researchers.

In sum, pairing CrimeStat IV with a free GIS, such as QGIS, makes for a powerful and free combination!