Hi Sander,
Obviously I don't have a professional scanner. But don't underestimate
the work. I think that three minutes per map would be rather
ambitious. The list contains more than 300 maps. A quick and probably
optimistic estimate is 1000 minutes or 17 hours of work just for the
scanning. While you are at it, including maps that will get out of
copyright in a few years might sound like a plan. Depending on where
you put the cutoff that could add another 100 (only 40's) to 300 (if
also including a good part of the 50's) maps that I have. Anyhow,
count on easily a week of work.
You are right, I don't want to invest that time in something that
might eventually maybe be useful myself. I'd rather get out and map
one of the many remaining white spots on the OSM map in Belgium.
You can't compare the quality of 20th century maps with the 18th
century Ferraris map. Most of the cartographic know how dates from the
19th century. I even don't think that Ferraris has a well defined
projection, while those topographic maps are a Bonne projection on the
Delambre ellipsoid. I assume that projection even has an EPSG code.
Also, from 1928 on the ICM (Institut Cartographique Militaire) started
working based on a denser triangulation. The precision is not like
modern maps, but certainly as good as the OSM precision.
wouter
On Thu, Sep 25, 2014 at 11:24 AM, Sander Deryckere <sander...@gmail.com> wrote:
> In 2010, we mapped a lot of boundaries using out-of-copyright maps. Though
> the maps we used were a lot older (mainly Ferraris maps).
>
> Today, there are still boundaries of the part-municipalities we could map
> using old maps like these.
>
> In my experience, a high-quality scan is the most valuable. Although
> mass-georeferencing them can be nice, we only did it on an individual base
> when mapping the boundaries (by using the background-image plugin for JOSM).
> Mainly because those old maps weren't drawn very correctly, we had to adapt
> the georeferencing based on the actual position where we were working. I
> have a feeling it won't be a lot better with pre-WWII maps.
>
> High-quality scans wouldn't cost that much effort with a professional
> scanner. Maybe it would be good to upload them to commons (so they can be
> used in Wikipedia) or on the OSM wiki. I think the most work will be to
> classify them, so they are searchable.
>
> Anyway, I think it would be nice, but I don't know how useful it would be,
> so I understand if you don't want to do it.
>
> Regards,
> Sander
>
> 2014-09-24 23:13 GMT+02:00 Wouter Hamelinck <wouter.hameli...@gmail.com>:
>>
>> Hi all,
>>
>> The talk on the list about the wiki with sources for Belgium reminds
>> me that I promised some months ago to make a list of out of copyright
>> topographic maps that I have. The list is below. Practically speaking
>> it are maps dating from before the second world war.
>> Those maps can be used for OSM and I am willing to provide them if
>> there would be a practical use. I am somewhat skeptical about their
>> usability, however. All maps are paper maps, so would need to be
>> scanned and georeferenced before they are really useful in my opinion.
>> Which is a lot of work that I am not willing to do.
>>
>> wouter
--
"Den som ikke tror på seg selv kommer ingen vei."
- Thor Heyerdahl
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