Table of Contents for
Practical GIS

Version ebook / Retour

Cover image for bash Cookbook, 2nd Edition Practical GIS by Gábor Farkas Published by Packt Publishing, 2017
  1. Practical GIS
  2. Title Page
  3. Copyright
  4. Credits
  5. About the Author
  6. About the Reviewer
  7. www.PacktPub.com
  8. Customer Feedback
  9. Dedication
  10. Table of Contents
  11. Preface
  12. What this book covers
  13. What you need for this book
  14. Who this book is for
  15. Conventions
  16. Reader feedback
  17. Customer support
  18. Downloading the example code
  19. Downloading the color images of this book
  20. Errata
  21. Piracy
  22. Questions
  23. Setting Up Your Environment
  24. Understanding GIS
  25. Setting up the tools
  26. Installing on Linux
  27. Installing on Windows
  28. Installing on macOS
  29. Getting familiar with the software
  30. About the software licenses
  31. Collecting some data
  32. Getting basic data
  33. Licenses
  34. Accessing satellite data
  35. Active remote sensing
  36. Passive remote sensing
  37. Licenses
  38. Using OpenStreetMap
  39. OpenStreetMap license
  40. Summary
  41. Accessing GIS Data With QGIS
  42. Accessing raster data
  43. Raster data model
  44. Rasters are boring
  45. Accessing vector data
  46. Vector data model
  47. Vector topology - the right way
  48. Opening tabular layers
  49. Understanding map scales
  50. Summary
  51. Using Vector Data Effectively
  52. Using the attribute table
  53. SQL in GIS
  54. Selecting features in QGIS
  55. Preparing our data
  56. Writing basic queries
  57. Filtering layers
  58. Spatial querying
  59. Writing advanced queries
  60. Modifying the attribute table
  61. Removing columns
  62. Joining tables
  63. Spatial joins
  64. Adding attribute data
  65. Understanding data providers
  66. Summary
  67. Creating Digital Maps
  68. Styling our data
  69. Styling raster data
  70. Styling vector data
  71. Mapping with categories
  72. Graduated mapping
  73. Understanding projections
  74. Plate Carrée - a simple example
  75. Going local with NAD83 / Conus Albers
  76. Choosing the right projection
  77. Preparing a map
  78. Rule-based styling
  79. Adding labels
  80. Creating additional thematics
  81. Creating a map
  82. Adding cartographic elements
  83. Summary
  84. Exporting Your Data
  85. Creating a printable map
  86. Clipping features
  87. Creating a background
  88. Removing dangling segments
  89. Exporting the map
  90. A good way for post-processing - SVG
  91. Sharing raw data
  92. Vector data exchange formats
  93. Shapefile
  94. WKT and WKB
  95. Markup languages
  96. GeoJSON
  97. Raster data exchange formats
  98. GeoTIFF
  99. Clipping rasters
  100. Other raster formats
  101. Summary
  102. Feeding a PostGIS Database
  103. A brief overview of databases
  104. Relational databases
  105. NoSQL databases
  106. Spatial databases
  107. Importing layers into PostGIS
  108. Importing vector data
  109. Spatial indexing
  110. Importing raster data
  111. Visualizing PostGIS layers in QGIS
  112. Basic PostGIS queries
  113. Summary
  114. A PostGIS Overview
  115. Customizing the database
  116. Securing our database
  117. Constraining tables
  118. Saving queries
  119. Optimizing queries
  120. Backing up our data
  121. Creating static backups
  122. Continuous archiving
  123. Summary
  124. Spatial Analysis in QGIS
  125. Preparing the workspace
  126. Laying down the rules
  127. Vector analysis
  128. Proximity analysis
  129. Understanding the overlay tools
  130. Towards some neighborhood analysis
  131. Building your models
  132. Using digital elevation models
  133. Filtering based on aspect
  134. Calculating walking times
  135. Summary
  136. Spatial Analysis on Steroids - Using PostGIS
  137. Delimiting quiet houses
  138. Proximity analysis in PostGIS
  139. Precision problems of buffering
  140. Querying distances effectively
  141. Saving the results
  142. Matching the rest of the criteria
  143. Counting nearby points
  144. Querying rasters
  145. Summary
  146. A Typical GIS Problem
  147. Outlining the problem
  148. Raster analysis
  149. Multi-criteria evaluation
  150. Creating the constraint mask
  151. Using fuzzy techniques in GIS
  152. Proximity analysis with rasters
  153. Fuzzifying crisp data
  154. Aggregating the results
  155. Calculating statistics
  156. Vectorizing suitable areas
  157. Using zonal statistics
  158. Accessing vector statistics
  159. Creating an atlas
  160. Summary
  161. Showcasing Your Data
  162. Spatial data on the web
  163. Understanding the basics of the web
  164. Spatial servers
  165. Using QGIS for publishing
  166. Using GeoServer
  167. General configuration
  168. GeoServer architecture
  169. Adding spatial data
  170. Tiling your maps
  171. Summary
  172. Styling Your Data in GeoServer
  173. Managing styles
  174. Writing SLD styles
  175. Styling vector layers
  176. Styling waters
  177. Styling polygons
  178. Creating labels
  179. Styling raster layers
  180. Using CSS in GeoServer
  181. Styling layers with CSS
  182. Creating complex styles
  183. Styling raster layers
  184. Summary
  185. Creating a Web Map
  186. Understanding the client side of the Web
  187. Creating a web page
  188. Writing HTML code
  189. Styling the elements
  190. Scripting your web page
  191. Creating web maps with Leaflet
  192. Creating a simple map
  193. Compositing layers
  194. Working with Leaflet plugins
  195. Loading raw vector data
  196. Styling vectors in Leaflet
  197. Annotating attributes with popups
  198. Using other projections
  199. Summary
  200. Appendix

Using QGIS for publishing

QGIS offers a very easy and convenient way to publish QGIS projects with its own spatial server. It is the CGI application QGIS Server, which we have already configured in Chapter 1, Setting Up Your Environment.

If you are using Windows, and could not configure QGIS Server properly, don't worry, just skip to the GeoServer part (Using GeoServer).

Similar to the popular UMN MapServer, QGIS Server is a simple CGI application which does not track the published data. While MapServer needs a configuration file where paths to the data sources are defined along with other configuration parameters, QGIS Server needs a QGIS project file, which contains the paths along with other information, like styling. We can provide the project file's absolute path in a map parameter.

While web servers can only access a portion of the file system, CGI scripts can access anything they have permission to read or write. Always consider this when using CGI scripts.

Let's craft a URL which queries the WMS capabilities of QGIS Server using one of our QGIS projects. As we are on the same machine as the server, we can use the placeholder localhost instead of a domain name or an IP address:

    http://localhost/cgi-bin/qgis_mapserv.fcgi?
     map=/home/debian/practical_gis/
      ch10.qgs&Service=WMS&Version=1.3.0&Request=GetCapabilities

The response should look similar to the following:

If you are using Windows, you might need to use the path http://localhost/qgis/qgis_mapserv.fcgi.exe to reach QGIS Server.

A long XML response shows if we have a working QGIS Server, which can access our projects. By installing QGIS Server, it automatically integrates itself in QGIS, and makes our projects publishable with WMS. To see what those published maps look like, we can use QGIS as a client. In order to load a WMS layer, we need to connect to a spatial server publishing WMS layers first, using the following steps:

  1. Click on the Add WMS/WMTS Layer button on the left toolbar.
  2. Click on New to define a new connection.
  3. Name the connection (it can be anything), and provide the URL to the QGIS Server application with the map parameter pointing at a QGIS project file (for example, http://localhost/cgi-bin/qgis_mapserv.fcgi?map=/home/debian/practical_gis/ch04.qgs). I will use the carefully styled map from Chapter 4, Creating Digital Maps.
  4. Click on OK to save the connection, and close the dialog.
  5. Click on connect to see every layer published as a WMS map.
  1. Select the topmost layer named after the project file to load every layer from the project. Add the whole map with the Add button:
If you experience character encoding problems with labels, you have to set character encoding explicitly. To do that, open the project you are using with QGIS Server, open Properties | General on the source layer of the problematic labels, and set the Data source encoding from System to the correct value.

We can see the styled layers, although there are two very conspicuous problems--there are some layers published which we had disabled in our project, and it uses the projection EPSG:4326, making the map look distorted. The overall composition is not very aesthetic, which we can resolve by opening the project in QGIS:

  1. Open Project | Project Properties from the menu bar.
  2. Navigate to the OWS server tab.

As QGIS Server serves projects, we can configure the behavior of the QGIS Server in the project properties. There are several general sections in the dialog which are useful for basic configuration, like the following:

  • Server capabilities: Basic metadata about the provider. If enabled and filled out, that data is supplied with the capabilities of XML by the server application.
  • CRS restrictions: QGIS Server can create WMS images in up to three CRSs by default. Two of them are the popular EPSG:4326 and EPSG:3857 CRSs. If the published project uses a third CRS, it can be also used by default. To customize the CRSs, WMS layers can be queried, we can enable CRS restrictions, and manage the allowed projections manually.
  • Exclude layers: By default, every layer in the project is published as a WMS image. In order to exclude some of the layers, we can add them in the Exclude layers section.
  • WFS capabilities: Spatial data is not published by QGIS Server in raw vector format by default. We can enable WFS layer-wise, by checking the Published box on the appropriate vector layers. We can also enable WFS-T (WFS-Transaction) on some layers (that is, Update, Insert, and Delete). The only requirement is that the layer has to be in a format QGIS can write in place.
  • WCS capabilities: Similar to WFS, we have to enable publishing raw raster data with WCS layer-wise.
Do not hesitate to try out WFS and WCS on some layers. Once enabled, you can request WFS and WCS layers with the Add WFS Layer and Add WCS Layer buttons similar to adding new WMS layers.

For now, let's only exclude the disabled layers from the WMS service.

  1. Add the disabled layers in the Excluded layers list with the green plus icon.
  2. Apply the changes, and save the project.
  3. Open a new project, or an existing one used for this chapter.
  4. Add every layer from the previously saved project as a single WMS layer as we did previously. Before adding the layer, click on the Change button next to the default CRS's name (WGS 84), and select the local projection we use from the list.
If QGIS Server still provides the excluded layers, remove the layer, and add a new WMS layer. This time though, do not select the parent layer named after the project file, but select every child manually. You can do that by holding down the shift key while clicking on each layer you would like to include.

Now we have a stack of styled layers ready to use in a web application:

The image we see is the same as we will see on our webpage if we use the layers with web-mapping software. This is the greatest benefit of using QGIS Server--as it uses the same libraries as QGIS, the served images will be the same as we can see in the project's styled layers in QGIS.