[OSM-talk] All you've ever wanted to know about the french cadastre

["Petr Morávek [Xificurk]"]

Richard Weait wrote:
> On Wed, Sep 26, 2012 at 12:59 PM, Olivier Croquette <ml at ocroquette.de> wrote:
> 
>> If no, it doesn't make any sense to me that a vector based process for the cadaster is an import, and a raster based is not. Everything is the same : kind of data, license, provider…
>>
>> There seems to be a contradiction there.
> 
> Yes, this is something of a contradiction or edge case.  May I offer,
> from my perspective, an important difference between tracing over
> raster, and copy / pasting vectors?  You say:
> 
> "Some cities (10% as an order of magnitude) have only a raster
> cadaster, in which case the mapper has to draw all the nodes and
> points manually."
> 
> I think that "drawing all of the nodes and points manually" is an
> important difference, from a quality point of view.  Each node or way
> that you draw by hand, is carefully considered and placed, one at a
> time.  It isn't perfect; nothing is.  I suggest that this leads to a
> kind of automatic quality control, as the nodes and ways are placed.
> 
> The goal of the vector import procedure is similar, use data from this
> area, reconcile it carefully, include it in OpenStreetMap.  The
> intention is very good.  But in execution, it is easier to miss a node
> or way (or more than one) that needs to be refined before upload.
> Again, it isn't perfect; nothing is.  When you are considering
> hundreds or thousands of nodes and ways at once, it becomes time
> consuming to check them all.
> 
> I hope that you'll find the above to be easy to agree with.
> 
> My conclusion, is this.  The quality of the hand drawn nodes and ways
> will be better because when we draw the nodes and ways by hand they
> get more individual attention and care than when we start with a group
> of nodes and ways from another file.
> 
> So that's why I think that it is different to trace by hand, vs.
> vector import.

I've read those paragraphs several times, but still don't really get
your logic. Are you claiming that from two options
1) check+manually trace the data,
2) check vector data,
the first one leads to a higher quality output?


My perspective is that man-hours are expensive commodity and we should
treat it that way and put it to a good use. And I don't think that
hand-tracing vector data falls into that category.

Best regards,
Petr Morávek aka Xificurk