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geoinformatics:webgis

Web-delivered GIS

Client-side and Server-side webGIS services

The project refers to online cartography and GIS services; in particular on the server side (back-end) development, where the main processing load is not undertaken by the device of the user, and the front-end web cartography, where the user’s computer, i.e. the client, retrieves data from a remote server, processes them accordingly and replicates them on the device’s screen.

At this point, it is important to clarify that the ‘server’ used for the purposes of the present exercises was not remote, but run on the same machine used for the development (localhost).

Server-side GIS services

The main steps followed for the completion of a server-side GIS delivery system can be outlined as follows:

  • Installation of the required software of the host machine
  • Creation of database, where the geography data will be stored (pgAdmin III)
  • Acquisition of the data (from internal repository) and upload to the database (using the designated tool (PostGIS2.0 Shapefile and DBF Loader)
  • Creation of a Web Map Service (WMS), workspace, set data source.
  • Creation of layers, one for each feature
  • Creation of a group layer, which, in practice, is the output map
  • Styling of all the layers

Client-side GIS services

This project is divided into two parts. The first part refers to the creation of a map which is compiled on the client computer, within the web browser. In the second part, a combination of a client-side and a server-side map is generated in the same session. The steps followed for both parts are outlined as follows:

  • Acquisition of data (OpenLayers 3)
  • Adjusting the code (javascript) to focus on Denmark, add and fine-tune a zoom slider, change the positions of the zoom-in and zoom-out buttons so that they are above and below the slider, add a zoom-to-max-extent button and fine-tune its placement, add a scale bar and a mouse coordinates indicator above it, also adjust its placement so that it is located right above the scale bar
  • Addition of a “theme selector”, which turns specific layers on and off and adjustment of its placement on the map application
  • Loading vector data: a vector layer with the municipalities of Denmark (Kommune) except for Viborg and adjustment of its appearance, and a layer of the forests of Viborg from the local WMS service (i.e. the local server at http://localhost:8080/geoserver/wms and layer name viborg:forests). It’s worth mentioning that the latter is layer originating from vector data, which is rendered by Geoserver into a raster layer.

Finished product

The map of Viborg, with the layers as rendered on Geoserver.

Zoomed-in at the center, where the different coloring in the build-up areas is visible. The coloring was made possible by styling the polygons according to their attributes.

Zoom-in at the Forests layer

The map designed ‘locally’, with the vector layer Kommune, which originated from a .json file, and the layer Forests, which was rendered on Geoserver and imported to the client-drawn map as raster.

geoinformatics/webgis.txt · Last modified: 2020/07/25 15:30 by sotosoul