[Talk-GB] Separation of sources

Simon Ward simon at bleah.co.uk
Tue Apr 6 08:01:03 BST 2010

On Tue, Apr 06, 2010 at 01:35:42AM +0100, Martin - CycleStreets wrote:
> I'm not sure I quite understand the objection to tracing over other
> data that OSM can legally and ethically use (though can appreciate
> David Earl's point of view).

There is no objection to tracing over other data, but an objection at
doing it at the expense of ground surveyed data.

> The fact is that this OS data is "our" data which mostly we as
> taxpayers have paid for already. Why shouldn't we make use of it and
> incorporate it as the basis of a road network that can then be
> incrementally improved, adjusted and built upon, more quickly (unless
> it is not 'good enough' from an accuracy perspective)?

Of course we should use the data available to us.  I don’t think it is
necessary to bung it all directly into the same project.  If all of the
different data sources are readily available online, a “combined”
project could use them, and improve on them.  Another project might
prefer to combine them differently.

> I agree in an ideal world, ground-surveys done from first principles
> will be preferable. But the fact is that there remain areas of the
> country that routing.

Given a selection of sources, it is up to the data users to combine them
in a way that works for them.  If a project needs the basic road
network, there’s nothing stopping it using GPS + OS + traced aerial
imagery + whatever, and combining them in a way it sees fit (well, short
of the effort in doing this that I may underestimate).

> volunteer-encouragement perspective. So wouldn't the pragmatic way
> forward be to patch in / trace over data in incomplete areas, so
> that it forms the basic network?

Again, I don’t see how separating out the sources stops this from
working in a combined project.  Maybe OSM now is the “combined” project,
I’d just like to see something where ground surveyed data is the
ultimate, and it’s not clear to me that it is the ultimate now.

> >If people want other sources so much, won’t they encourage the
> >effort to combine the independent sources?

> I think that surely underestimates the effort required. Processing
> one massive dataset is bad enough, never mind having to do this for
> several sources and find ways to deal with merging/clashing.

Oh, I expect it would be extra effort.  You snipped the bit where I said
that.  I asked “is it really that bad?”  I’m very much not a data user
at the moment, so I have very little experience, so do tell me more. :)

A complex system that works is invariably found to have evolved from a
simple system that works.—John Gall
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