I am sorry for not having the time to follow up on this in more depth. The remarks in my reply from Nov 17 mostly still stand. I am not deep enough into the matter to reliably asses if the concerns raised there are warranted but i also have not seen any replies convincing me they are not. I admit though this goes quite deeply into the technical foundations of LIDAR data processing and due to the lack of more detailed information on the process issues raised were fairly vague.
This touches the subject of how much you can, when planning and organizing an import, trust assertations of external experts (usually data providers with their own interests not necessarily in sync with the OSM community) regarding properties of their data and suitability of the processes used. In normal mapping we do this to some extent (think of GPS device producers, aerial imagery providers) but these cases are either technically simple or easily accessible for in depth reliability checks and cross comparison with other sources even for a layman. This is different when you have a complex and largely intransparent and not publicly documented process, no access to the raw data (raw LIDAR by the way means point cloud data, not some kind of gridded product) and at best an overall statistical error assertation. You can do spot tests on the final data all you want - it is still something fundamentally different from normal mapping in OSM, which is done with full understanding and control over the whole process from the primary data. Ultimately i think OSM can only work if everyone entering data - either as a normal mapper or through imports (and in that case both the ones preparing and the ones actually entering the data) is accountable for the data he/she imports. And being accountable has two components: (1) the acceptance of responsibility for what you do and (2) the ability to substantially carry this responsibility by having a sufficiently well-founded ability to assess the quality of the data you enter with respect to the real world situation. The main aim when planning and performing an import must not be to add additional data but it needs to be to allow you and your fellow importers to responsibly and productively participate in the community process of open map production. If i read people justifying imports in general independent of how they were made because they add useful data this appears quite misguided to me. I could easily produce many gigabytes of useful information i could enter into OSM but i won't do that if i am not convinced this is valuable for OSM as a community *independent of the value of the information itself*. All of this does not mean you should not import building heights for SF. But discussion needs to stay clear of the fruitless level of overall quality assertations, the pointless concentration on the value and usefulness of the data and the sweeping dismissal of concerns as unfounded. I have seen a lot of positive things in the planning of this import but when i read some of the replies to Frederik i am once again flabbergasted by how people can dismiss concerns just because they apparently don't understand them. It is completely fine to articulate diverging experiences and opinions but in return you also need to respect the views of others and that those might be valueable - even if you do not comprehend them. -- Christoph Hormann http://www.imagico.de/ _______________________________________________ Imports mailing list [email protected] https://lists.openstreetmap.org/listinfo/imports
