I've seen this on several buildings in Vienna in Innerstadt, a few weeks ago. Wondered what exactly it meant.
This seems to be something used for surveying. The logo on top seems to indicate it's from a civil engineering company.
I tried to look for projects this could be related to both on the webpage of the city administration survey service and the project website of the construction company, however, I can't find anything specific. It could be used for a construction project or to measure subsidence.