What is a WMS?
WMS (=Web Map Service) is a geographic information server (GIS) database that contains different map layers. To use these types of maps, you need to connect to the server and choose the map layer or layers that you want to use. The WMS maps that you use in Maptionnaire should be in WGS84/EPSG: 4326 or 3857.
WMS maps are reliable and easy to use, with many cities and municipalities having their own WMS servers with maps for different needs. If you need to display a large quantity of features on a map, instead of using heavy (=several MBs in size) shapefiles or GeoJSONs, we recommend using a WMS layer. WMS layers tend to be much easier to access on different devices and browsers when it comes to extensive geographic detail.
Please note that you should not try to enter the URL of the map layer into Maptionnaire, but the general URL connecting to the WMS server. Layer choices are made once Maptionnaire has established a connection with the server.
How to upload a WMS layer?
Go to Materials, choose the Maps tab and click Add Map on the upper right corner. Choose Add WMS layer from the drop-down menu. You can also add the layer directly in the questionnaire editor in the Maps section of the main settings.
Enter the WMS server URL in the window that opens. If the WMS map that you are using requires an API key, you can enter it in the section URL Parameters.
Once Maptionnaire has established a connection to the server, you should choose the layer or layers that you want to use in your survey by typing their names in the Layers section. If for some reason the map layer does not appear as in the image above, try turning the Transparent tiles setting on.
- You should also choose the Server type (usually named in the WMS URL).
Other settings that you can change or add:
- Name and Description.
- Control label that will be used as the map layer title if several map layers are used in a questionnaire.
- Attribution, which will be displayed on the lower right corner of the map.
- Layer opacity allows you to adjust the opacity of the layer.
- In Tile format you can choose the image format for the map tiles from the drop-down menu. It is strongly recommended that you choose image/png if possible. The server may automatically specify another format.
- Set the Zoom range for the map server. This should be the range for which the map server can produce tiles. Setting an incorrect range can make your map load slowly or not show up at all. Most servers support the range 1 to 19, and in general you should not need to change the lower end value of the range. If the map server supports very detailed views, you can increase the upper end of the range up to a maximum of 25. If the map layer disappears at high zoom levels, try lowering the upper end of the range.
Finally, click Create item, or Save if you are editing the settings after creating the item.
How do I use this map in a questionnaire?
For more information on how to use maps in questionnaires, please see Questionnaire backgrounds
I uploaded a WMS layer but can't get it to work. What could be wrong?
This could be due to several reasons. Here are some of the most common:
- Check that the server URL is correct.
- Check that the WMS is in or supports the coordinate system WGS84:4326.
- Choose a map layer(s) that you want to show. You can do this under Layers in the map editing window in Materials.
- Check that you are zoomed in close enough. Sometimes WMS servers only produce map tiles when you zoom in closer to the location on the map.
- Check with the person(s) responsible for that WMS server that the server allows web-based platforms such as Maptionnaire to use its maps. What they should be looking at are CORS settings and specifically the 'Access-Allow-Control-Origin' setting, which should be set to "*".
- Remember, you can always contact firstname.lastname@example.org for help!