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<p>Hi</p>
<p>Your proposed workflow would seem to be totally OK to me and is
clearly not an import. List the government data in the sources
used in the changeset and IMHO you are good to go.</p>
<p>Simon<br>
</p>
<div class="moz-cite-prefix">Am 04.09.2021 um 12:51 schrieb Little
Maps:<br>
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cite="mid:1216B6F6-FC17-4B96-A7AD-A587529DBF45@gmail.com">
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<p class="p1" style="-webkit-text-size-adjust: auto; margin:
0px; font-stretch: normal; font-size: 20.4px; line-height:
normal;"><span class="s1" style="font-size: 20.38px;">Hi all,
my understanding is that the process described below is a
big filtering exercise rather than a data import, but since
I’ve never been involved in an import before, I’d like to
check before progressing. Thanks in advance for your
feedback.</span></p>
<p class="p2" style="-webkit-text-size-adjust: auto; margin:
0px; font-stretch: normal; font-size: 20.4px; line-height:
normal; min-height: 24.3px;"><span class="s1"
style="font-size: 20.38px;"></span><br>
</p>
<p class="p1" style="-webkit-text-size-adjust: auto; margin:
0px; font-stretch: normal; font-size: 20.4px; line-height:
normal;"><span class="s1" style="font-size: 20.38px;">Goal: to
update road surface tags across regional Victoria where
necessary. Many surface tags were added 8-10 years ago and a
surprising number of roads have been surfaced since then.
(I’m only interested in sealed/paved vs unsealed/unpaved
options, not subsets of these.)</span></p>
<p class="p2" style="-webkit-text-size-adjust: auto; margin:
0px; font-stretch: normal; font-size: 20.4px; line-height:
normal; min-height: 24.3px;"><span class="s1"
style="font-size: 20.38px;"></span><br>
</p>
<p class="p1" style="-webkit-text-size-adjust: auto; margin:
0px; font-stretch: normal; font-size: 20.4px; line-height:
normal;"><span class="s1" style="font-size: 20.38px;">Method:
compare road surface data in OSM against data in the Vic
government’s transport dataset which we have permission and
waiver to use. All rural roads from motorways to
unclassified (not residential, service, etc) that have
different tags in OSM and the gov dataset will be examined
against satellite imagery and Mapillary, and any decisions
on whether to update the surface tags will be made based
solely on the imagery. No data will be directly copied from
the gov dataset. Hence, as I understand osm’s import
guidelines, this is a big filtering exercise rather than an
import. Is that a correct interpretation? I’ve added a
longer explanation below to help answer any questions.</span></p>
<p class="p2" style="-webkit-text-size-adjust: auto; margin:
0px; font-stretch: normal; font-size: 20.4px; line-height:
normal; min-height: 24.3px;"><span class="s1"
style="font-size: 20.38px;"></span><br>
</p>
<p class="p1" style="-webkit-text-size-adjust: auto; margin:
0px; font-stretch: normal; font-size: 20.4px; line-height:
normal;"><span class="s1" style="font-size: 20.38px;">Basic
assumptions: (1) I assume both datasets were made
independently, as I’ve not seen any evidence that OSM
surface tags were copied from the Vic data (or that the gov
copied from OSM). (2) If the 2 independent datasets both
indicate the same surface then I assume it is most likely to
be correct. If they indicate different surfaces then one
must be in error. At the outset, I have no idea how accurate
the Vic gov dataset is, so I’m not assuming it is infallible
(it’s definitely not; see comment below). </span></p>
<p class="p2" style="-webkit-text-size-adjust: auto; margin:
0px; font-stretch: normal; font-size: 20.4px; line-height:
normal; min-height: 24.3px;"><span class="s1"
style="font-size: 20.38px;"></span><br>
</p>
<p class="p1" style="-webkit-text-size-adjust: auto; margin:
0px; font-stretch: normal; font-size: 20.4px; line-height:
normal;"><span class="s1" style="font-size: 20.38px;">Methods:
for every road segment that has a different surface tag in
the 2 datasets, I’d inspect the road using available
imagery, as is normally done when adding or updating a
surface tag. Existing OSM tags will either be altered or
retained, as required. There’s no ambiguity involved in
updating a tag from unpaved to paved. It’s much less common
to need to update a tag from paved to unpaved. Again, this
will be done based on imagery, regardless of what the Vic
data says. </span></p>
<p class="p2" style="-webkit-text-size-adjust: auto; margin:
0px; font-stretch: normal; font-size: 20.4px; line-height:
normal; min-height: 24.3px;"><span class="s1"
style="font-size: 20.38px;"></span><br>
</p>
<p class="p1" style="-webkit-text-size-adjust: auto; margin:
0px; font-stretch: normal; font-size: 20.4px; line-height:
normal;"><span class="s1" style="font-size: 20.38px;">Some
prelim observations: I’ve trialled the method in NW Vic,
where the method works fine on longer road segments/ways.
The approach would have to be restricted to ways > 1-2 km
long, and short ways will be ignored. From an initial subset
of about 50 roads > 5 km long in NW Vic, I found about
2/3 of the discrepancies between the 2 datasets did not
warrant any change in OSM and about 1/3 did. The Vic gov
data doesn’t seem to be as up-to-date as the imagery and
isn’t by any means perfect. Regardless, the approach looks
to be a very effective way to find out-of-date and
inaccurate road surface data across the state.</span></p>
<p class="p2" style="-webkit-text-size-adjust: auto; margin:
0px; font-stretch: normal; font-size: 20.4px; line-height:
normal; min-height: 24.3px;"><span class="s1"
style="font-size: 20.38px;"></span><br>
</p>
<p class="p1" style="-webkit-text-size-adjust: auto; margin:
0px; font-stretch: normal; font-size: 20.4px; line-height:
normal;"><span class="s1" style="font-size: 20.38px;">At this
stage I don’t know how many ways will be examined or
changed, as it will depend on the minimal length of road I
inspect. I’m envisaging about 1000 at the max, and probably
fewer.</span></p>
<p class="p2" style="-webkit-text-size-adjust: auto; margin:
0px; font-stretch: normal; font-size: 20.4px; line-height:
normal; min-height: 24.3px;"><span class="s1"
style="font-size: 20.38px;"></span><br>
</p>
<p class="p1" style="-webkit-text-size-adjust: auto; margin:
0px; font-stretch: normal; font-size: 20.4px; line-height:
normal;"><span class="s1" style="font-size: 20.38px;">My guess
is that, if the process was completed across Vic, then the
surface data in OSM would be extremely accurate, and more
accurate than in the Vic gov database. If I get through
enough of it without going bonkers, I’m interesting in
summarising the findings to show which discrepancies were
most common, etc.</span></p>
<p class="p2" style="-webkit-text-size-adjust: auto; margin:
0px; font-stretch: normal; font-size: 20.4px; line-height:
normal; min-height: 24.3px;"><span class="s1"
style="font-size: 20.38px;"></span><br>
</p>
<p class="p1" style="-webkit-text-size-adjust: auto; margin:
0px; font-stretch: normal; font-size: 20.4px; line-height:
normal;"><span class="s1" style="font-size: 20.38px;">So, back
to the original question, is this process ok to pursue,
given that the sole function of the gov dataset is to
provide a filtering mechanism to identify roads to
investigate, and all decisions will be made based on legally
available imagery, not the gov data?</span></p>
<p class="p2" style="-webkit-text-size-adjust: auto; margin:
0px; font-stretch: normal; font-size: 20.4px; line-height:
normal; min-height: 24.3px;"><span class="s1"
style="font-size: 20.38px;"></span><br>
</p>
<p class="p1" style="-webkit-text-size-adjust: auto; margin:
0px; font-stretch: normal; font-size: 20.4px; line-height:
normal;"><span class="s1" style="font-size: 20.38px;">Thanks
very much for your feedback, Ian</span></p>
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<br>
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