I am fairly new to osm contribution so please forgive me my ignorance.
I am using streetcomplete in order to provide information. A lot of missing information is the street width, type of house, etc. Or each fire department must know the diameter of the hydrants but they are missing on the maps. Shouldn’t all this information be already available and (publicly) accessible? Probably even in a simple database so that everything could be mapped very easily.
This sounds so easy that there must be a problem with it. Is it the licensing?
I can’t answer for your city or Germany, but on a worldwide scale, all of the following factors make mapping from public sources much more complicated than you suggest:
The data is simply not available to the public. Historically that has been a very common situation.
The data is available, but not in a format that can easily be used for mapping (e.g. you might be able to access Cadastral records for one property at a time, but not as a mass query).
The data can be accessed by the public, but is not available under a license suitable for OSM (note that OSM can be used commercially, for example, so any data we use must allow commercial use).
A related problem: it may not be clear what license applies to the data, and it may be difficult to find somebody in the relevant official body with the authority to confirm that it can be used.
The data is simply not good enough, e.g. it is outdated, incomplete, or inaccurate. This is much more common in “official” data than you seem to think. E.g. somebody recently tried importing the location of recycling bins in my city from the city council’s database. The location data placed many of them within buildings, on the wrong side of the road etc. The work involved in manually reviewing them is probably similar to what would have been involved in adding them via StreetComplete in the first place. It is very discouraging to “on the ground” mappers to have to spend time correcting errors imported from official data.
The data is difficult to conflate with data already in OSM. E.g. uploading building footprints from Cadastral data in a city that is already fairly well mapped with buildings is very difficult.
Even if none of these problems apply, importing the data may require a level of technical knowledge (e.g. database query languages) that most mappers do not have.
Or: there may not be any mapper interested enough to do so. We all have limited time for mapping, so we need to make choices about what we contribute to the map. Maybe there simply doesn’t happen to be anybody mapping in your city who wants to spend time on the diameter of fire hydrants.
alan_gr has already provided a comprehensive summary of the problems with access to free public data and the “simple” import of those.
Not much to be added except probably the fact, that even in an industrialized country like Germany not all public data are digitalized and the public sector is lightyears away from a central database where we could find everything we would at least like to have a look at (not to talk about simple import into OSM). Public data are spread all over the republic and in some cases it’s even hard to find out where to get certain data from. Trying to get any kind of information from public sources can be frustrating as I can tell from own experience.
Again most of the data OSM could be interested in are not business of the federal government but of the state governments and the “open data” concept has not yet reached all of them. In some federal states everyone has free access to cadastral data, in other states not yet. But even if you are lucky to have free an unrestricted access to these date you would get some georeferenced plot and house shapes, house numbers and some basical landuse information (not even always acutal) but nothing about road width, tracks, cycleways, type of buildings, location of fire_hydrants or the like.
That’s why acutally micromapping is mainly done by local survey by people like you (and me and many others) …
