[Talk-us] hydrology Alaska

Ben Discoe bdiscoe at gmail.com
Tue Oct 17 23:40:51 UTC 2017


+1 to what AlaskaDave said.

As far as I can tell in this case, the jaggies are a result of running
ScanAerial on imagery of a low resolution (i.e. zoomed out).  At that
level (LandSat resolution), a smooth lake edge looks like a jagged set
of individual pixels, where each pixel is 28 meters across.  Turning
each LandSat pixel into a vector edge produces these unattractive,
stair-setpped, inefficient polygons.

Please don't do that.

I don't know ScanAerial well, but it seems to me that you could run it
on a higher resolution (the Bing database/API has much better than
LandSat resolution here, if you zoom in).  The resulting polygons
would then need to run through a Simplify, to remove excessive detail,
before they could be uploaded to OSM.  That should result in
appropriate number of nodes, e.g. that smooth top edge of lake.

Anton, I can produce illustrations, if you need more help to understand.

If ScanAerial cannot be configured that way, then it's simply the
wrong tool to use for this situation.

On Tue, Oct 17, 2017 at 2:52 PM, Dave Swarthout <daveswarthout at gmail.com> wrote:
> The tracing for that pond ( https://www.openstreetmap.org/way/532622119) is
> horrible IMO. This is the sort of geometry that drives me crazy when I look
> at Alaskan coastlines. The long zig-zag at the top edge could be better done
> with a few points and the adjoining ponds at the SE are very rough
> approximations at best. I don't know what method you used to draw that pond
> but please don't add any more that look like that one.
>
> I have done extensive work in Alaska and I appreciate your intent to add
> more Alaskan water bodies to OSM but please find another way to add them.
> There are thousands of tiny ponds dotting the permafrost in northern Alaska.
> Using your tracing technique will add hundreds of thousands of points, many
> of them useless.
>
> Dave
> (AlaskaDave)
>
> On Tue, Oct 17, 2017 at 8:01 AM, ANT Berezhnyi <velmyshanovnyi at gmail.com>
> wrote:
>>
>> (sorry for my english)
>>
>> question:
>>
>> On 2017-10-16 02:33:13 UTC velmyshanovnyi
>>
>> http://www.hdyc.neis-one.org/?velmyshanovnyi
>>
>> wrote:
>>
>> ===============================================================
>>
>> so on the question ...
>>
>> Is it possible to vectorize the USGS on the OSM if there is no Landsat,
>> and everything else in the clouds, or in the snow, or the quality is bad ...
>>
>> Hello velmyshanovnyi , There are a number of questions here. One is "is it
>> possible to vectorize the USGS". Another is "is it a good idea to do so".
>>
>> I'd suggest that you discuss what is the best source of imagery in this
>> region with other mappers, such as "imagico" who commented on
>> https://www.openstreetmap.org/changeset/52947504 . It may be that you need
>> to use several sources and combine them manually because none of them are
>> perfect. Also I would suggest asking on the talk-us and talk-ca mailing
>> lists for advice.
>>
>> With regard to "is this a good idea" other mappers think it is not. You
>> need to persuade them that it is. You need to explain what your process is.
>> Your comment on https://www.openstreetmap.org/changeset/52947504 that says
>> "Im fixed my soft" suggests that you might be performing some kind of
>> mechanical edit. If so, you need to follow
>> https://wiki.openstreetmap.org/wiki/Mechanical_Edit_Policy , which requires
>> you to discuss what you are proposing to do with other mappers before
>> actually doing it.
>>
>> Best Regards,
>>
>> Andy Townsend, on behalf of OSM's Data Working Group.
>> https://www.openstreetmap.org/user/SomeoneElse
>>
>> ================================================================
>> My sample island/hydrology (JOSM+digitalglobe-premium+bing) not import,
>> not bot :
>>
>> https://mc.bbbike.org/mc/?lon=-164.973165&lat=60.843461&zoom=13&num=2&mt0=digitalglobe-premium&mt1=mapnik&mt2=hike_bike&mt-1=ol_osm-no-labels&mt-1p=35
>>
>> after simplifacation (v2) :
>>
>> https://www.openstreetmap.org/changeset/52809320#map=16/60.8221/-164.9684&layers=H
>> (before see v1)
>> ================================================================
>>
>> IF:
>> if there is a need to correct some hydrology somewhere - welcome ))))
>>
>>
>> --
>> ++ =========================================
>> ++ ANT (Anton Berezhnyi)
>> ++ =========================================
>> ++ E-mail   : velmyshanovnyi at gmail.com
>> ++ Hangouts : velmyshanovnyi at gmail.com
>> ++ Telegram : @velmyshanovnyi
>> ++ Skype    : velmyshanovnyi
>> ++ Viber    : +380939946993
>> ++ Cell     : +380939946993
>> ++ https://plus.google.com/+ANTBerezhnyi
>> ++ https://profiles.google.com/velmyshanovnyi
>> ++ https://linkedin.com/in/velmyshanovnyi
>> ++ https://facebook.com/velmyshanovnyi
>> ++ https://twitter.com/velmyshanovnyi
>> ++ =========================================
>> ++ жNtTя, яК і iTNernЕТ,
>> ++ нAЖалb, ТЕж к0лИСь
>> ++ KіH4аЄтьCя..
>> ++ =========================================
>>
>>
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>>
>
>
>
> --
> Dave Swarthout
> Homer, Alaska
> Chiang Mai, Thailand
> Travel Blog at http://dswarthout.blogspot.com
>
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