How Does MATLAB process OSM File for Buildings' Shape and Height and Elevation?

Hi all,

I'm trying to create 3DOccupancy map by using OSM files obtaining from OpenStreetMap. I'm trying to extract information of buildings and terrain elevation so that I can reproduce 3DOccupancy map to apply path planning algorithms on it. With many diffrent operations, I can obtain buildings shape, height (not sure if it is true), and terrain elevation by open elevation online using its geodetic coordinate. However, there is a mismatch between those altitudes and maybe the height of the buildings with what I have imported into UAV Scenario. This makes it impossible to simulate since there is a little mismatch between altitudes such that given path waypoints' altitude also mismatch.

Here is an example of what I have been trying to explain.

And

Here you can see that I succesfully extracted building shapes and reproduced on 3DOccupancy map. However, I have taken the height information of the buildings from the minHeight and maxHeight. Elevation is taken by open elevation api by using geodetic coordinates. However, as you can see there is around 40 meters mismatch.

How MATLAB process these informations and how can I reproduce it? Is there an easy and exact way such that I won't deal such a altitude mismatch.