[Tagging] how to map soft story/soft storey buildings properly?

Michael Patrick geodesy99 at gmail.com
Thu Dec 20 08:57:05 UTC 2018


> A few years ago, there was an effort (promoted by World Bank, it seems) to
>  map buildings in OSM for Katmandu where they used key
buidling:soft_storey=yes/no.
> They never proposed a formal tag. The results of that effort is a bit
confusing and I'm not sure it's the best approach.

Because their may not have been very many of these left after multiple
earthquakes?
Wikipedia isn't probably the most authoritative source on this subject.

First, it might be noticed that the term, even in OSM, is not used in
isolation, it is part
of an extensive internally consistent system of terms from a survey of a
particular part
of the world. i.e it only helps designates the probability of hazard when
all the other
factors in that tagging / survey scheme are also noted.

'Soft_storey' is part of a rapid VSM ( Rapid Visual Screening) process
( see Table 3 at https://bit.ly/2S60CE6 for a global list of these, The
U.S.A. FEMA https://bit.ly/2QKVhp5 )
In the western United States, designating a building as a 'soft_story'
visually with the intended meaning that it was at seismic risk, you
would be off base. Many seismic retrofits, especially in historic
buildings are invisible. And many with visible mitigation have
other characteristics in the coding scheme which make them
seriously at risk. The FEMA RVS is 388 pages because the
assessment is not trivial. Seismic vulnerability is the sum total
of many aspects.

> how to map soft story/soft storey buildings properly?

Use on of the recognized seismic VSMs that apply to the location.
GEM ( https://www.globalquakemodel.org ) is global, and has rapid
VSM survey sheets for various countries
https://docs.wixstatic.com/ugd/1dcea4_e0c3391c6d32439188f8969ed902f0d6.pdf

>  Question for the community: does it make sense to add soft story
> information using the key building:soft_storey=y/n (similar to
> https://wiki.openstreetmap.org/wiki/Key:building:fireproof) or should I
use
> building:structure=soft_storey?

If you intend to give meaningful accurate seismic information, it
should be the lowest level concept and only be present if the other
characteristics are included, ideally, from a survey.

> Good question. For disaster preparedness and response, it is valuable to
> have a list of soft story buildings in a neighborhood. There are multiple
> places where such buildings are mapped like ....

They examples you gave make an interesting point. Who
maintains this in OSM, i.e. if a retrofit is accomplished, do you
still designate it as soft story? What about addresses which
are demo'd and new construction? Also, for various reasons,
many, many retrofits are not done under a permit, or not
specifically identified as a seismic retrofit. One of those, the city
program site, has mostly 'exempt' or 'done' entries, and those
appear on the map anyways. Same with the City of SF site,
and a quick Streetview of the few non-compliant ones show
no residential occupancy, just the ground floor retail is
open.

For disaster preparedness and response, accurate
information is important, in these cases, 'the map'
practically useless.

However, what I think what you want to do is still
possible and could be really, really useful, if it
followed a format ( like one of the VSMs) that
provided the complete set of characteristics.And
those tags should be prefaced with something like
'GEM_soft_story' that makes it clear they are part
of a set, not an end conclusion about the building's
risk. And you would have to timestamp it some way
to refresh it.

Michael Patrick

( another kind of soft story
https://en.wikipedia.org/wiki/Millennium_Tower_(San_Francisco)#Sinking_and_tilting_problem
)
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