Video: Free and Open Source GIS Reference Data

After last week's post looking at the landscape of free and open source GIS software, the next logical step is looking at open GIS data. This video looks at reference data. I am still deciding on what to do the next video on...the choices are a) Open data portals, b) novel data types, social media (TwitteR and Instagram), or c) remote sensing.  Let me know what you would like to see in the comments below.

Topics covered in the video include:
Census: https://www.census.gov/geo/maps-data/data/tiger.html
DataFerrett: http://dataferrett.census.gov/
Summary File 1 DVD: https://www.census.gov/mp/www/cat/decennial_census_2010/summary_file_1_1.html
Natural Earth: http://www.naturalearthdata.com/
OpenStreetMap: https://www.openstreetmap.org/
GeoNames: http://www.geonames.org/
US Board on Geographic Names:http://geonames.usgs.gov/domestic/index.html
Maryland Department of Planning/ACS: http://www.mdp.state.md.us/msdc/S7_ACS.shtml

An Introduction to OpenLayers 3, Part II

Last week, we created a basic web map by loading a basemap from OpenStreetMap using OpenLayers 3 (OL3).  If you missed last week's post, below are links to the code:

• Click to view the text file
• Click for the HTML file 

This week I will cover copying OL3's JavaScript libraries to a web hosting service. Also, note that you can run basic OpenLayers code off your computer--it simply depends on where the sources of data are located and how the code is written.

In order to get your map visible on the web, you will need a web hosting service or your own server.  After setting up an account, you will have a chance to upload files. Before that, there are a few things you need to know:

• You will upload folders and files from the OL3 JavaScript library to the public or root directory of your web hosting service.  
• In some cases, this is simply a matter of placing files in a folder; for some services you may have to set permission levels to public/everyone.
• An additional step for uploading and accessing layers.
•  In the next post, we will upload, use, and symbolize this uploaded layer.  
• OL3 runs client-side (vs the server) so keep that in mind, so you won't want to use this method for large layers.
• You don't need to do this step or the next one if you are accessing layers using a web map service or WMS.
• Later I will also look at using GeoServer for more complex layers.
• In addition, you will have to create a simple web config file to access files on your web hosting service. 
• This can be done in a text editor, like Notepad. 
• For example if you plan to use KML files, you will have upload a file with the following code for particular media or MIME types. 
• Click to magnify the screenshot below for an example for a *.kml file.

You can find code for other MIME types by searching the web.
Save this code as web.config and upload to the root directory of your web hosting service.

After downloading and unpacking the *.zip file from OL3 (or OL2), you will see several folders and files. 

• Consider copying all the folders and files over to see examples and understand how the code works
• Keep in mind how you copy folders and files over, since this will affect how you write code and reference directories.
• Lastly, the ol.js file you need is in the build folder.  In the first example that I showed (in the code above), you need to change the link to the OL3 website from "http://ol3js.org/en/master/build/ol.js" to "build/ol.js."  The same goes for the css stylesheet.

Next time, we will look at uploading, using, and symbolizing a KML.

For serious developers, be sure to check out the OL3 wiki at: https://github.com/openlayers/ol3/wiki

An Introduction to OpenLayers 3, Part I

OpenLayers is a JavaScript library for creating interactive maps on the web. Basically, these libraries are referenced to help facilitate the development process, providing a basic foundation and advanced features.  I will devote several posts to OpenLayers 3 (OL3) which is currently in its beta release.

This first post will demonstrate some of the basic code and functionality of OpenLayers, and why you should consider using it.  Later posts will cover topics that build logically on one another and include moving and copying files to a web host, symbology, and allowing for user interaction (and feedback) with a map.  Lastly, we'll look at incorporating other free and open source GIS software, such as GeoServer.

OL3 will improve on its predecessors with a more streamlined code, better templates, and documentation. For a brief history of OpenLayers, head over to Wikipedia.  OpenLayers can handle a wide range of map-related files and extensions.  It is client side (I will talk more about this in later posts).

OL3 will improve on OL2.

Loading a Basemap
A logical starting point is loading a basemap, which many maps and map apps utilize.  One of the earliest decisions you may face:  ow much of the user's screen a map should take up.  For the web version, visit: http://webmapexamples.net/OSMBasemap.html.  Feel free to zoom and pan.  Other open basemaps, for example Stamen maps, can also be loaded. A screenshot appears below:

As seen in Mozilla's Firefox web browser

You can download the code with comments in a text file here or html file, which you can experiment with after downloading to your desktop.

A different sized map is at: http://webmapexamples.net/OSMBasemapv2.html.  A simple change to the height of the style was made and is highlighted in red.

  <style>
      .map {
        height: 350px;
        width: 100%;
        }
    </style>

Initially, OL3's learning curve remains fairly steep.  However, coding appears to be much more efficient than OL2 and gets easier over time.  Advanced functionality can be easily added, a definite bonus!  An early OpenLayers 3 workshop is available here (note: try reloading the page).  Tutorials, examples, and documentation are still being produced.  Looking ahead, at least two books will be published to assist you:

• OpenLayers 3: A Beginner's Guide
• The Book of OpenLayers 3

Next time, I will write about moving and copying OL3's libraries. to a web hosting service and getting them on the web! I will also talk about key additional steps and importing common layer files such as KML files.

3D Visualization of Manhattan using QGIS Plugin

GIS Blogger Anita Graser, aka Underdark, has created a nice visualization using the QGIS2threejs plugin, including an interactive web-based version.  I won't repeat the instructions listed on her blog, but I will make a few suggestions as I go along. Her eloquent map features buildings extruded (constant height), trees, and some elevation changes. Feeling inspired, I thought I would give it a quick try.

If you just want to see the visualization, visit: http://webmapexamples.net/3DExample/Cityscape.html

Note: You will need Firefox, Chrome, or Internet Explorer 11--basically a Web-GL capable browser to view the visualizations.

WebGL is an API that allows for 3D visualizations to be displayed in a web browser without additional plugins. So, users won't need to install anything to view your product.  The threejs plugin is a JavaScript library that helps to keep everything neat and tidy.  For examples of threejs projects, check out this website: http://threejs.org/ which is filled with examples of featured projects.  Believe it or not, the projects you will see below consist of five files that take up less than 5 megabytes of storage.

Tip #1: Using a shapefile or digitizing a boundary for an extent can help to speed the project along and keep the look of your map consistent.  In QGIS, you can do this using the AutoTrace plugin.

For the project, I focused on Manhattan from Central Park down to just below times square.

Below is what the project looks like in QGIS.  I left the bound on to show the project area.  I used a building footprint shapefile that contained height from New York City's Open Data Portal.  Please note: This file is large ~ 180 MB.  In addition, there is a basemap from Open Street Map using the QGIS plugin, and a DEM.  You can also add other point, polygon, or line features to your 3D map.  I have chosen to stay with just buildings.  I color-coded the buildings based on height for effect (redder is taller).  Click on any of the screenshots to magnify them.

Project area and files 

Running the plugin is rather quick.  The result is five files exported to a folder of your choosing.  The contents of the folder can be placed into the root or public directory of web hosting service to publish to the web!  Of course, you can also double-click the resulting *.html file to open it on your desktop--please note some broswers may try to block you from opening it.  So right-click, and choose open with a friendly browser like Chrome or Firefox.

Tip #2:  I created a new variable to half the building heights.  Otherwise, the tall buildings of NYC barely fit in the web browser and makes viewing awkward and challenging.

You can view the visualization at: http://webmapexamples.net/3DExample/Cityscape.html

When you first open the html file, the view will be oriented the same way you have the files in QGIS.  If you have not used 3D viewers before, you can navigate using the left and right mouse buttons and wheel to  pan, rotate, and zoom.  Try not to make sudden moves with the mouse because it is easy to get disoriented. Refreshing the web page will send you back to the starting view.

3D Visualization of Manhattan.  Redder buildings are taller.

As you zoom and pan, you can bring areas into closer view.  Here looking down 7th Avenue in NYC.

A closer look: From Central Park down 7th Avenue

Lastly, an overhead view of Times Square...

Can you see where the ball is dropped on New Year's...One Times Square?

Overall, the plugin was fast and easy to use.  Not only can it be used for creating cityscapes...You could also visualize chloropleth maps in 3D, for example.  Performance in browser was smooth.  I saw memory usage similar to what Underdark reported, around 1.6 GB of RAM.  This is reduced if you do not constantly hold down any of the mouse buttons--occasionally releasing as you view.

Update #1: If the basemap is not loading, and you see a black rectangle, reload/refresh your browser once or twice and it should appear!

Update #2: Forgot to mention: Since almost 2 GB of RAM is used--this prevents viewing the maps on a mobile device, since most mobile devices don't have or max out at 2 GB.  I have gotten them to load in Android after a long time, but you won't be able to manipulate them (zoom, pan, rotate,etc.)

OpenStreetMap.org

OpenStreetMap.org (OSM) provides users the ability to edit and download street maps for free through open source licensing.  Check out more background information about OSM at Wikipedia.

Open source GIS software like QGIS also have add-ons to aid in the download process. Alternatively, you can download the data directly from its website or connect to a WMS server.  You can also use OSM maps as base layers in Open Layers for web publishing.

Companies, including Apple, have recognized OSM's value--Apple uses OSM in its iPhoto app.  Most of the map's symbology is relatively straightfoward, but you can also check out its wiki to find an extensive list.  Below the Florida keys are shown. Click the photo for a more detailed image.  Be sure to check out this terrific resource!


The Florida Keys