[gdal-dev] Why are fields required in osmconf.ini file?

[Djordje Spasic]

Thank you for the information once again Jukka!

    On Sunday, December 4, 2016 6:03 PM, jratike80 <jukka.rahkonen at maanmittauslaitos.fi> wrote:
 

 Brad Hards wrote
>> Why is that so? Why do field names need to be predefined before their
>> extraction from the .osm file?
>>
>> Why can't only those fields which already exist in the .osm file, be 
>> extracted?
> How could ogr2ogr possibly know what fields are in the file? It would
> require 
> a full parse of the file, and likely give you many more fields than you 
> possibly want in any case.
> 
> Brad

Especially with shapefiles it is also practically impossible with any bigger
datasets.  Dbf file can have only 255 fields, or 254 if fields may contain
NULL values https://msdn.microsoft.com/en-us/library/3kfd3hw9(v=vs.80).aspx.
There are 1012 different tags in the Irish OSM data today
http://taginfo.openstreetmap.ie/tags. It means that there are 758 more tags
than it is possible to save as fields into shapefiles.

-Jukka Rahkonen-




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