# How to specify key:building:levels?

Hello everyone!

Please, could you help me - how to specify the Key:Buildings:Levels correctly?

I made a basic, simplified model to show typical issues that disturbing me https://ibb.co/tmQsCw2:

1. Occasionally, buildings have a basement level that is partially visible from the ground level https://ibb.co/tmQsCw2 and https://ibb.co/P1rzX62. Sometimes there are fully functioning floor inside (offices, gyms, etc.) or just engineering communications. What is the correct way to take into account such a level? I would count it as 0,5, or even 0.4, but I’m not sure if this is the right approach. Also, there is another thing, is it make sense to use more accurate numbers for these not typical levels such as 0.3 or 0.4 etc. or is it worth conditionally specifying 0.5 and not diving into the details.

2. Also, I’m not sure how to deal with penthouses correctly, because according to https://wiki.openstreetmap.org/ roof and attic should not be counted. According to my logic, penthouse level is a full-fledged floor. I also want to share a photo of the building https://ibb.co/GRtHgD7 - how would you consider the number of floors at the top of the building? I would say, it contains 8 levels. Is it correct?

3. I also have a question, what to do with technical floors? How would you calculate this level https://ibb.co/mS11CF9?

Finally, according to my logic, the schematic building https://ibb.co/tmQsCw2 has a 3.5 levels (or even 3.4 since the visible part of the basement is less than half of the basement or typical levels). Am I right?

Thank you very so much in advance!

https://wiki.openstreetmap.org/wiki/Key:building:levels “number of above-ground levels” so basement would not be counted at all.

Sometimes it is tricky when something starts counting as above-ground level, but it would never be 0.4 of level - either 0 or 1.

https://prnt.sc/20xew0y is either building:levels=3 or building:levels=4, I would likely use the second variant based on provided image but 3 also would be OK

(yes, building level count depends on mapper - and anyway building:levels=4 may be higher than building:levels=5, even if both have flat roof)

https://prnt.sc/20xewjb clearly has 8 levels - there is no attic or levels within some sloped roof.

Thank you so much, Mateusz!

But the tricky part that in this article below https://wiki.openstreetmap.org/wiki/Key:building:levels “Values should be positive numbers. Fractional values (like 1.5) are also valid. They are in common use in 3D tagging”. Based on this information, I thought that it makes sense to take into account the basement, which is partially immersed in the ground and partially visible at ground level and indicate it as 0.5, since the real basement floor level is much lower than the ground level: https://prnt.sc/20xkn6r. It seems to me that fractional numbers allow you to end up with a more accurate 3D model.

I also have a question, what to do with technical floors https://prnt.sc/20xkqai? How would you calculate this level?

There’s no standard meaning of fractional levels. People have suggested their use for various things (basements with windows, levels with sloping ceilings, technical levels, …), and it’s impossible to tell what a particular mapper wanted to express with a fractional value.

So the answer at the moment is that there is no proper way of showing these details in OSM 3D models yet. I understand it’s not a particularly satisfying answer.

Thank you very much, Tordanik!

I really hoped to find some accepted and general rule regarding this question, but the more I search, the more I understand that there is no unified answer and everything just depends on the mapper vision

But it seems to me that it is very important to accept some general rule, since everything is very dependent on the background of the mapper, the specific country and the characteristics of the building. I understand that this is a very difficult question, but otherwise this key becomes even more approximate (there are so many other nuances here, since the height of the floors can be also very different etc.). It might make sense to collect specific examples, analyse them and include this information on the https://wiki.openstreetmap.org/. At the moment, I will continue to collect some specific examples, try to collaborate with other mappers, and I hope this can help us over time.

You links don’t work

Hello Maro21!

Thank you for your response! To be honest, I don’t know what is the problem with them, since everything is working for me and the members above. But just in case, I uploaded everything to another hosting - I hope this time there will be no such problem.

3D building tags work best if exact heights are added to the building (with key:height) but this can be challenging.

Hi Ireige,
If you plan to do more of that kind of work, consider buying yourself a digital distance meter with the height value option build into it. There’s one trick you can’t use it in full daylight or buy a system without a red dot of the laser, I use it indoors and ad the wall thickness later. The measurement of a lock basin is tricky during daytime or find a dark spot beneath a bridge.

Hello Goedegazelle!

Yes! This is really the best way, but also more complicated and sometimes almost impossible (or maybe I just don’t know some secret approach)… ( And when we don’t have such information, building:levels are also not bad, but of course, the final height will be absolutely approximate. However, this is better than nothing and because of it, I try to adjust numbers which will provide us more realistic 3D results.

Hello Hendrikklaas!

This is what I am going to do! At the moment, I am looking for a good tool + it is also necessary for my regular job. Could you recommend some proper company or product?