Ian/all
I have been boldly marking paved and no-tag as asphalt,
causeways/fords/bridges as concrete (etc) as a result of examining my
own Mapillary imagery, sometimes dovetailing that with the DCS data.
These are not only regional highways, but backroads and most of small
towns.
I actually use the overpass query to help route plan, deliberately
checking those with no tag. The query also showed a number of really
strange errors, like only the ends of a rural road are paved in real
life, yet an entire road was paved (with a surface tag) on OSM (West
Wilcannia Rd from Menindee to Wilcannia for example)
https://www.openstreetmap.org/changeset/98337907
My Garmin GPS unit with an OSM based map tries to route me down unpaved
roads too.. Good surface information will give credibility to OSM map
data for general navigating.
I'll admit I have concerns that my surface tags for a paved highway
might be removed, so I welcome the change.
Bob
On 31/1/21 3:13 pm, Little Maps wrote:
Hi folks, wondering if I can promote some discussion about the section
of the Aus tagging guidelines on adding surface tags on roads. The
text currently reads,
“For most types of highway=* tags you don't need to specify the
surface=paved key/value pair as this is assumed, however make sure you
tag the road surface when it isn't a paved road.”
This assumption is fine in large cities but is problematic in rural
and regional Australia. Can I suggest that it is replaced by something
like the following...
"Surface tags should be added to roads wherever possible, especially
in regional areas. This advice differs from that on the international
key:surface wiki page, which states that, 'there is normally an
assumption that the surface is surface=paved unless otherwise stated.'
However this assumption is not valid across regional Australia as: (1)
most roads, including many major roads, are unpaved, and (2) mapping
intensity varies greatly among regions. Many roads that do not have a
surface tag may not have been examined by mappers. Adding a surface
tag will assist data users and help mappers to further refine the
regional road network."
Long rationale (not for posting on the oz tagging guidelines page)...
Surface tags have been added to relatively few rural roads in many
regions. Hence, the most prudent assumption is that the absence of a
surface tag means that the road surface has not received attention
from mappers. A default assumption that any road without a surface tag
is actually paved is most likely wrong.
Efficiency of mapping. Even if one has no interest in adding tags to
paved roads, the most efficient way to refine surface tags is to
interrogate untagged roads and tag them (e.g. by using an overpass
query that distinguishes untagged, paved and unpaved roads, and
variants thereof. Untagged roads can be inspected and tagged as
appropriate.) However, if mappers are advised to not tag paved roads,
then every paved road that is untagged needs to be re-examined each
time this is attempted. This wastes a lot of effort.
Some apps — especially routing and cycling apps (e.g. Osmand and
Komoot) — allow users to request paved or unpaved routes. Regardless
of the (unknown) assumptions that routers make about road surfaces
when creating routes, apps like Osmand present the data back to users.
The suggested route may be X% paved, Y% unpaved and Z% unknown. In
many regions, Unknown is the largest category. This doesn’t inspire
confidence in the route or underlying data.
Some assumptions about road surfaces can obviously be made. For
example, a primary road is more likely to be paved than an
unclassified road. However, most roads in rural areas are tertiary or
unclassified. Some are paved, many not; the ratio varies unpredictably
across regions and it is impossible to predict which roads are paved
unless they are tagged.
Perhaps not surprisingly, the OSM wiki on key:surface gives
conflicting advice, beginning with the (European?) position that
“there is normally an assumption that the surface is surface=paved
unless otherwise stated” and later adding an (American?) view that,
“There are no default values for surface, it is generally considered
as OK and desirable to tag it explicitly for all roads.” The latter
approach seems most appropriate in regional Australia.
Adding surface tags to both paved and unpaved ways is the most
efficient method to: (1) allow data users to accurately predict road
conditions (this benefits users) and (2) improve the rate at which
unpaved roads can be reliably distinguished from paved roads (this
helps future mappers). They may be redundant on motorways, trunk and
primary roads, but these make up a tiny proportion of roads in
regional Australia and can all be coded with a minimum of effort.
Advising mappers to not add a meaningful tag would appear to be
counter to the goals of accurate tagging. Can we change our advice to
encourage mappers to add a surface tag wherever possible?
Thanks for your time, I'm keen to hear your thoughts. Best wishes, Ian
_______________________________________________
Talk-au mailing list
Talk-au@openstreetmap.org
https://lists.openstreetmap.org/listinfo/talk-au
_______________________________________________
Talk-au mailing list
Talk-au@openstreetmap.org
https://lists.openstreetmap.org/listinfo/talk-au
