Preparing the OpenGovernment TreeCadastre of Vienna for OSM-import (2)
As Friedrich Volkmann from the Austrian OSM-Mailinglist proposed, the single entries from the OpenGovernmentDataset “Baumkataster” do not only include trees, but also shrubs. So, this dataset would better be named “Wood Cadastre” than “Tree Cadastre”. The problem hereby is, that the definition for the OSM tag “natural=tree” only includes trees. So, there has to be applied an additional filtering mechanism. Friedrich proposed to make the decision based on the height of the tree in relation to his age.
I implemented his proposal by checking if the tree is smaller than 2 meters while older than 3 years:
height <= 2 and (int(datetime.datetime.now().year) - year) >= 3
Additionally to this, it would be best to define unique rules for each of the over 90 types of trees. But this is a huge amount of work and in my opinion it is questionable whether this leads to better results or not. After doing some experiments it all comes down to only a handful of trees which would be excluded. With the current general implementation this comes to 678 trees.
It is important to mention that any tree excluded by this method is not ignored but still imported. The difference is, that it is assigned another special tag: “fixme=Baum oder Strauch” (tree or shrub). Only by checking manually the real habit of the plant can be determined.
Andreas Trawoeger is currently working on a yet to be released live-preview-map which is overlaying the trees of the OGD-dataset with the ones already inside OSM. This will give a better overview of the extent of the dataset in question.