Hi,

This email refers to the mapping of individual parking spaces 
amenity=parking_space within car parks amenity=parking, where the car park is 
also mapped. It does not refer to ad-hoc groups of 1-5 parking spaces. A few 
mappers have mapped like this. I’ve long been sceptical about the practice but 
haven’t acted. And, while it might be marginally useful (even ‘cute’) to show 
the spaces, it feels like 'mapping for the renderer'. Mapping the car park 
outline and the parking aisles probably achieves as much, but with much less 
effort.

Specific issues that I have encountered: 

* It is double mapping, which can result in the number of spaces, in total or 
in any category, being miscounted. OSM has the principal of one object in the 
real world, one object on the map. Yes, there are sometimes complications that 
need nuanced mapping, but I don’t think this is one. 

* Some car parks have dedicated wheelchair-accessible, family-friendly, bus or 
other special category parking spaces. Double counting them might be a 
particular problem - someone expecting 4 bus parking spaces at a site shows up 
to find that there are only 2. Yes, showing people where the special category 
parking spaces are located is useful, but these are usually located according 
to a (not always obeyed) hierarchy of what is closest to the destination 
entrance - public transport, bike spaces, wheelchair accessible spaces, 
family-friendly spaces, electric vehicles, other vehicles.

* The number of spaces are sometimes miscalculated by the mapper, e.g. there 
are 9 parking spaces in a row, but only 8 are mapped covering the area of the 
9. This results in a need to change all the individual spaces, instead to only 
one car park. 

* During the lifecycle of the parking space, details can change. For example, 
the Blanchardstown Centre has 7,000 parking spaces (not all mapped) that are 
being converted to pay parking.

* When a car park is removed / built upon, potentially hundreds of individual 
parking spaces have to be retagged / removed. There were 867 parking spaces in 
this temporary car park: https://www.openstreetmap.org/way/1167858985 and they 
are now all gone. There are approximately 1,431 parking spaces in these car 
parks, with a chunk of them now built on: 
https://www.openstreetmap.org/way/1296475241 and 
https://www.openstreetmap.org/way/1365517863 Hundreds of more spaces have been 
added in the real world (not yet mapped). Grange Castle probably has 8,000 
parking spaces (not all mapped), most of them are temporary spaces for 
construction workers that will disappear in 1-2 years.

Overall, it creates an unnecessary maintenance burden, especially when mappers 
want to add more tags or deal with removal.

There is a separate, but similar issue of car parks (with say 50 spaces) being 
mapped as several separate car parks (say 5 car parks each with 10 spaces), for 
fear of mapping across a non-parking aisle service road, path or patch of 
grass, e.g. here: https://www.openstreetmap.org/way/1429772350/ or here: 
https://www.openstreetmap.org/way/42873673/ or here: 
https://www.openstreetmap.org/way/905605692

Any thoughts?

Thank you

Colm



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