Let me explain in more detail, sorry for not doing that the first time:

Your graph from a few days that more and more slow roads are being adding,
does not necessarily means that we miss a lot of slow roads. Perhaps people
are just adding cycleways and sidewalks next to existing major roads.
This will also make it difficult to compare numbers from other sources
(thinking of frtutellake's approach that you now mention). Perhaps they do
not have those separate ways/lines for sidewalks/cycleways.

Total length is also a problem when one source represents a highway with 1
way/line and the other uses 2 lines.

So my "be careful" means that you should not compare 2 road networks from
different systems without knowing all the details, nor that you can draw
conclusions from more and more slow roads being added.



Of course there is no problem with an overlay to find differences.


regards

m




On Thu, Nov 12, 2015 at 12:56 PM, joost schouppe <joost.schou...@gmail.com>
wrote:

> Marc,
>
> The way to do this would be to overlay NGI data with our data. You could
> do like frutellake did and check total length in squares of 1 kmĀ². Or you
> could do it more properly using a data conflation tool. With something like
> FME I would try to find a partner road for roads that exist in NGI. In case
> there is no match, that would warrant closer inspection. When a road is of
> a completely different type in NGI and our data, that would warrant a check
> too.
>
> I did this in a purely visual way with Wegenregister, which is mostly NGI
> but only Flanders, and there were places where NGI was more complete - and
> places where we are more complete.
>
> 2015-11-12 11:27 GMT+01:00 Marc Gemis <marc.ge...@gmail.com>:
>
>>
>> On Thu, Nov 12, 2015 at 9:43 AM, joost schouppe <joost.schou...@gmail.com
>> > wrote:
>>
>>> if only to check for missing roads in our map (especially the "slow
>>> roads" still need work in Belgium).
>>
>>
>> You have to be careful with this. People are now drawing cycleways and
>> sidewalks next to main roads. This means that the number of slow roads is
>> increasing, while they are not really missing.
>>
>> That does not mean that we have all the slow roads yet (paths & tracks) ,
>> but does anyone else have all of those (so we could compare) ?
>>
>>
>> regards
>>
>> m.
>>
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>
>
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