In Holland we use a tool offered by the government to get the height data based of NAP (Nieuw Amsterdams Peil), the tool works but it's kind of clunky and inefficient.


Anyone can login using username: rws with password: nap. It's in dutch but if you zoom in on the map you will see the locations of these "bolts" and there is some data attach to each of them. Now I am wondering if I could make a HTTP GET request to get access to this data. For example, I could make an app where the user inputs a address or coordinate and it would automatically generate a map and a list with these height bolts and there data.

There are sites that seem to supply all kinds of geo data but I am having trouble finding these bolts with "exact" height data. http://geodata.nationaalgeoregister.nl/bag/wfs?service=WFS&request=GetCapabilities&. Opengis is more of a international organization and they also provide an API to access data in JSON or XML but I'm not sure they have data about these specific height bolts in The Netherlands. http://schemas.opengis.net/gml/3.1.1/base/gmlBase.xsd

How can I get an X amount of these bolts with height in XML format through a HTTP GET Request for a random location.

edit It seems the following should yield the server capabilities of the CKAN API: https://geodata.nationaalgeoregister.nl/napinfo/wfs?request=GetCapabilities but it results in a error.

The following URL does yield a abstract feature which is what I am actually looking to "GET" from a specific measuring point: https://geodata.nationaalgeoregister.nl/napinfo/wfs?service=WFS&version=1.1.0&request=DescribeFeatureType&

That link tells me it is possible to somehow access specific measurement bolts and show me the height, locations in the wall, the name, date of measurement, etc. I just have no idea how to create a proper GET request to get these objects near a address or coordinate.

  • I see that both the GetCapabilities responses seem to be being returned, just not a mime type understood by a browser as a web page WFS and WMS. Note you need to specify the service= parameter not just the request= parameter. – nmtoken Apr 19 '16 at 20:02

Yes, I think accessing the WMS or WFS services of the Nationaal Georegister is the way to go.

Just for reference, here is the link to the WMS service: https://geodata.nationaalgeoregister.nl/napinfo/wms?

I had no trouble accessing it in QGIS, and using the Identify button, I could access the true NAP data for points.

Your question is not so much about accessing the NAP services, but more generic how to access geometry or attribute properties of a WMS or WFS service. I can't help you with that, but I am sure some more searching or reading on the internet should result in plenty of articles and tutorials of how to do this.

  • So for a WMS you should look at the GetFeatureInfo request, which allows you to get at details for the underlying data set for an image coordinate (i,j) in a GetMap request. For a WFS you should look at the GetFeature request. – nmtoken Apr 19 '16 at 20:16

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