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<font face="Verdana">If Ottawa had a crowd who had done a considerable
amount of GPS based mapping then I would totally agree with you. My
sampling has been done with a hand held WAAS GPS unit used whilst
walking, I am not comparing the original OSM roads to the Geobase data
but to a hand held GPS unit. The Geobase tagged data seems to have a
much closer agreement with the GPS unit.<br>
<br>
I used to work for Statistics Canada and I did some work in quality
control in industry so I am aware that my samples to verify what is
there so far doesn't prove everything is bad unfortunately I am also
aware that the probability of the rest of the data being dubious
increases with every new error found.<br>
<br>
One concern comes from talking to people who are interested in trees in
Ottawa. They like the idea of taking a photograph with a time stamp on
it so its GPS position can be determined then have a more knowledgeable
person identify the tree more exactly. The city centre looks like its
about 30 meters out. Currently I have identified a fire station being
roughly 100 meters off. One road was more than 100 meters off at one
end, causing parts of other roads to be omitted on the import. Are we
saying the the tree people take your photo and the GPS coordinates put
it on our map but accept that it might appear 100 meters away from its
location? I honestly don't think this data is based on a GPS trace.<br>
<br>
></font>If you are in the area that you are looking at the best, and
really
only, option is to check out the area yourself with a GPS and to
correct any discrepancies regardless of if they were made by a
individual mapper or as part of the GeoBase import. It is possible to
modify the data regardless of the source and doing so improves the
map. Replacing all of the user contributed data automatically with
GeoBase data is not the answer and can even cause errors because the
GeoBase data is not always the most current either. So update, and
correct, the data regardless of the source by physically checking it,
preferably with a GPS.<br>
<br>
<font face="Verdana">I agree with this statement as well however given
the current known resources in Ottawa then I think it is better to go
clean import from Geobase so we have a known quality of data then use
groups such as the residents associations, the bus fanatics, the tree
huggers whose primary interest may not be mapping to improve the
result. That way we end up with something usable quickly. We are
leveraging on the resources available. However to leverage them I have
to be able to say to them this is something useful for you today, not
when we have done a GPS survey and corrected the map it will be
useful. Current known resources are one person who lives in the
suburbs walking with a GPS unit and there are a lot of roads to cover.
I haven't come across a community of OSM mappers who party every week
in Ottawa.<br>
<br>
To me OSM is not a printed map in the traditional sense but a GIS
system which means the ability to add tags easily is very important.<br>
<br>
</font>>The data contributed by all contributors should stay
regardless of the apparent quality.<br>
<br>
The OpenStreetMap wiki about imports (<a
href="http://wiki.openstreetmap.org/wiki/Bulk_Importing"
target="_blank">http://wiki.openstreetmap.<wbr>org/wiki/Bulk_Importing</a>
) clearly states:<br>
<br>
"Bulk imports are undertaken as a supplement to data collected by
individual volunteers, and their data and ability to work in an area <i>always</i>
has priority."<br>
<br>
which
should be well regarded as a guideline for all of the imports in Canada
and abroad. They do not differentiate between good quality and poor
quality work nor about the apparent quality of the imported data. And
the imported data varies in quality as well. Some of it is very high
quality Differential GPS but other areas are of a lower quality.<br>
<br>
<font face="Verdana">I'm permitted to correct any data in an existing
map, so "data contributed by all contributors should stay regardless of
apparent quality" only means what I want it to mean.</font><br>
<br>
<font face="Verdana">These are general guidelines drawn up in Europe
where the ratio of GPS equipped mappers to road distance is quite
reasonable. Ottawa does not have the same resources and I think in
this particular case we should look for a more appropriate solution. I
think the issue is a local one, I'm not asking
for this for everywhere in Canada and I think the decision should be a
local one. So far I have not seen any input from some one doing OSM
mapping in Ottawa.</font><br>
<font face="Verdana"><br>
Cheerio John<br>
</font><br>
Gerald A wrote:
<blockquote
cite="mid:8e0ed1e00910280755p756be504nfe431c92adb4b2e7@mail.gmail.com"
type="cite">Hi,<br>
<br>
<div class="gmail_quote">On Wed, Oct 28, 2009 at 9:52 AM, john whelan
<span dir="ltr"><<a moz-do-not-send="true"
href="mailto:jwhelan0112@gmail.com">jwhelan0112@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><br>
I accept that just because Geobase data is from the government it does<br>
not mean that is is 100% accurate but it is consistent. Roads do<br>
connect which is important when putting together routing information.<br>
</blockquote>
<div><br>
</div>
<div>I'm not local to Ottawa, so you can take this with a grain of
salt.</div>
<div><br>
</div>
<div>First, I have mapped some stuff in the Toronto area which was
"adjusted" better with the Geobase data. It really discouraged me from
participating, because why actually map</div>
<div>when someone else will do it different "better" eventually? I
think this goes against the crowdsource we draw upon. It's better to
add where there are no maps, so you won't step on anyone's toes.</div>
<div><br>
</div>
<div>Second, not all the data seems to be connected -- around here,
hardly any of it was, making it entirely worthless for any purpose but
casual observance on the slippy map. Further, consistent and wrong is
still wrong, and I think we should try to produce a map that is
correct, not "consistent". (And there is wrong bits in the import data).</div>
<div><br>
</div>
<div>So, my suggestion would be import what we don't have, rather
then trash what another mapper has worked on -- and be aware that the
import might not be what you hope it is. It does move us forward, but
we need people on the ground to verify and expand it.</div>
<div><br>
</div>
<div>Thanks,</div>
<div>Gerald.</div>
</div>
</blockquote>
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