[Imports] Tanzania roads manual import

Christoph Hormann chris_hormann at gmx.de
Sat Aug 22 11:55:59 UTC 2015

On Saturday 22 August 2015, Rafael Avila Coya wrote:
> You can't imagine how many times and for how long I have thought
> about this idea of removing by software and beforehand the MSD&JSI
> road segments that are already present in OSM. The advantage would be
> very clear: we would save a lot of time and effort for the import
> users. But at the same time, I also spent quite a few hours going
> around the data, and my conclusion is that a good number of MSD&JSI
> are an improvement of their OSM counterparts. And I think it would be
> a pity to miss this oportunity of improving many of the existing OSM
> roads geometries.

I understand that - my reasoning however is that if a road is 
significantly worse in OSM as it is it won't be close to the better 
data along its whole length so it would not be filtered out anyway.  
Based on the data shown i would estimate even with a very tight 
threshold you could remove at least about 30% of the ways, especially 
among the shorter ones in more urban context which would already reduce 
work a lot.  And even if you miss a few cases of useful improvements 
this would be more than made up by the mappers' time freed to be spent 
on new genuine mapping.

Alternatively you could also make available the full data as gpx in 
addition to the reduced selection specifically suggested and prepared 
for import.

> There are for sure areas where most roads are already mapped in OSM,
> specially around big towns and cities. But this dataset will grow the
> total road distance in OSM from the aprox. 55,000 km that we have now
> inside Tanzania to around 115,000 km, so this means that around 52%
> of the MSD&JSI road segments aren't mapped in OSM yet. That's the
> average.

Note that's road length, not number of ways.  Most of it is smaller long 
distance roads which are not in OSM yet.  These seem to be the main 
value of the data for OSM and would not be affected by any automatic 
filtering, neither would roads that are only crudely mapped in OSM 
right now.

> [...] My suggestion for the workflow in these
> areas would be something like: "1) For segments still not present in
> OSM, we import them, but we will avoid adding the surface tag (we
> could instruct the mappers to add a fixme="Please, add surface tag").
> 2) For segments already mapped in OSM, we won't import them (ignore
> them)."

Yes, that's a good idea.

Christoph Hormann

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