[Imports] San Francisco building heights import
chris_hormann at gmx.de
Fri Dec 2 17:27:56 UTC 2016
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.
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