BAG data _ Indications on basement

Datasets BAG
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Dear Geoforum community,

I would like to define whether or not a building in the BAG dataset has a basement or not. I wonder if the attribute “ground-0.0” is negative, it means that you have a built under the level 0 of the house. Is that correct? If not, is there a way to define this on the BAG dataset?

Thank you!

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Hi @mdg, I’m not familiar with a attribute “ground-0.0” in the BAG…
From which datasource are you getting this information? (a URL would help)

As far as I know the BAG only has a attribute for the total square dimensions/floor area (gebruiksoppervlakte). What a total is of all the floors (probably including a basement, if available) in a bag verblijfsobject (residence?)

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Hi @mdg,
Wouter is correct. The BAG doens’t have a registration for the amount of floors or whether there is a basement or not.

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4

Hi @mdg, I assume you are working with the 3D Bag dataset by TU Delft. The ground attributes represent elevation values from the AHN dataset. Data Layers - 3D BAG

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I do think so too. And btw, in that case it doen’t mean that the building is below the 0 level of the house, but that it is below mean sea level (NAP-height).

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Hi @mdg , I spotted a few things in your question that need some attention in my opinion.

  1. The attribute ground-0.0 was part of the previous version of the 3D BAG, which was replaced in March 2021. Here is the announcement of the new version on this forum: The new 3D BAG is released - BAG - Geoforum , and you might need to check the documentation to navigate the new data model Data Layers - 3D BAG
  2. There are buildings in the Netherlands below the mean sea level (0m), as noted above.
  3. In the new 3D BAG we modify the original building footprints (from the BAG), and remove the parts from the footprint that are underground. This process is not super accurate and if we chop off part of the footprint it does not guarantee that there is a basement. It can also be some error in the input data, error in the algorithm etc.
  4. At the moment we discard these underground parts, because they are not needed for anything. Thus in order to find out if a building has underground parts, you would need to calculate the geometric difference between the BAG and the 3D BAG footprints.
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