[Qgis-developer] Adding default OSM backround maps

[Greg Troxel]

For context, I've only been lurking and intend to use QGIS when I get
time.  I have been an OSM mapper for 8 years.

Paolo Cavallini <cavallini at faunalia.it> writes:

> Il 21/03/2017 15:58, Jorge Gustavo Rocha ha scritto:
>
>> 1. The UserAgent is already a configurable feature in QGIS (under
>> Options/Network). Any user can change it, but we can propose another
>> default value.
>
> thanks - so, which could be the right default?

OSM data is freely usable, but there is a tile usage policy for the OSM
Foundation's servers:

  https://operations.osmfoundation.org/policies/tiles/

According to the policy, QGIS would probably need permission to offer
tiles from OSM servers.  The server admins might well be ok with this --
generally cooperation among Open Data and Free Software is great -- but
they are trying to serve tiles to the world without a big budget.

One of the guidelines is about user agent, which is aimed at less
configurable programs, to be able to identify and/or block things that
use too much server capacity.  So the notion of easily user-configure
UserAgent string sent to OSM tileservers should probably be discussed
with the OSM server admins.  I find configuration here strange; I would
expect the UserAgent string to be something that just looks like "QGIS
2.18".   But probably I have misunderstood.

Note that bulk downloading of tiles is not allowed.  If they are loaded
only when the user pans/zooms, that's ok.  But you can't prefetch a
large area to make that work faster or offline.  (See local rendering
commenta at the end.)

Another part of the usage policy is caching.  Clients must cache tiles
for at least 7 days by default.

I'm unclear if this discussion is only about using OSM as a base layer
within QGIS, or also extends to publishing created maps on the web such
that web users would load tiles.  Generally, OSM tileservers are
intended to support OSM itself, and for low-usage applications.  So it
might be that for publishing it would be good to ask people to check
that they've read the tile usage policy.


>> 2. The QGIS community is very much aware of OpenStreetMap. If we really
>> need to make our users more aware, does it make sense to add a new
>> button to QGIS to report map errors? (context dependent, when the
>> OpenStreetMap layer is shown) It would have the same functionality of
>> the notes in OpenStreetMap web interface.
>
> sounds good to me, and I assume also for OSM board

Yes, but as a mapper I would really like to see people sign up for an
account and have non-anonymous notes.  It's not that I need to know
their True Name, but two other things:

  An anonymous note cannot be used as the basis for editing, only to go
  check yourself, because the anonymous note writer has not necessarily
  agreed to the contributor terms and we don't know where the info came
  from (could be copied from another map).

  You can't ask for clarification.

Still, anonymous notes are useful, if one is local enough to be going by
or make a small detour at some point, or if the issue can be confirmed
by acceptably-licensed sources.

>> 3.1 On the "add layer" dialog, we can show the OpenStreetMap url (which
>> might change over time) and licenses (for data and tiles) taken from
>> settings or an (external) resource. We can make this not hard coded, to
>> be modified easily, without upgrading QGIS. We can also check if the
>> service is enabled for us, before allow users to add that layer (related
>> with 4.).
>
> sounds good

I am guessing you have some new-layer database which is kept fresh, and
enabling QGIS as a project to disable/change the OSM layer if there are
issues sounds good.  (I realize nothing stops anyone from doing
anything, but the point is to be able to protect OSM servers from large
numbers of users of a program who did not actually evaluate the
decision.)

>> 3.2 When the tiles are used in the composer or on the web client, we can
>> not enforce an attribution string. We might add or suggest it, but users
>> should be free the create and edit the attributions. It the
>> responsibility of the user, not a QGIS responsibility.
>
> sounds good to me, have to check with OSM

Legally, you may well be right.

Socially, if you have a facility to add OSM, then by default, adequate
attribution should be added, so that someone who does not understand how
to set up attribution or does not understand that they must will end up
doing thte right thing.

It's fairly frequent for OSM people to come across unattributed use and
ask for correction.  So I think the OSM community would appreciate it if
by default this came out right.  Not adding attribution by default is
sort of like offering to download a copy of QGIS'S source code with all
the copyright statements removed :-)

The fact that someone can remove it intentionally is not your
fault/problem.

>> 4. We have to handle when tiles are not loading, either because there
>> are network problems, server busy, etc. We can customize the user's
>> feedback regarding the load of the default OpenStreetMap tiles. But we
>> definitely need to know formally when they shut our access down. This is
>> related with 3.1 issue. If the access is disabled, we can also disable
>> adding default OpenStreetMap tiles option.
>
> it makes sense to me
>
> so, Jorge, would you like to help with coding this?
>
> all the best, and thanks.

Another thing to consider is including a renderer and having the user
download an extract.  viking (a less-than-GIS GPX/map viewer) has
support for this as well as using OSM tiles:

  https://sourceforge.net/projects/viking/

But compared to QGIS, almost no one uses viking.
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