[talk-ph] better ways to coordinate coastline mapping?

Tue Jul 6 03:17:02 BST 2010

Ah I get it ... So it detects node strings that form a "step" (a horizontal
and a vertical combination).  It may be good to make mappers aware that such
a combination will trigger sawtooth detection by Eugene's script.  For there
are some coastline contours that are indeed on a step shape.  Good way to
avoid it is to move the nodes just a bit so the longitude/latitude pairings
would not be exactly the same.  I found this out on one of my Marinduque
island edits.

thanks!

On Tue, Jul 6, 2010 at 9:31 AM, maning sambale
<emmanuel.sambale at gmail.com>wrote:

> @ ed,
> The technique is outlined here:
>
> http://wiki.openstreetmap.org/wiki/Talk:WikiProject_Philippines/Coastline_Corrections
>
> Couple of suggestions:
> 1. short link to the coastline correction wikipage
> 2. enable link to editors only at higher zoom level (perhaps 15-17?)
> 3. should be an osm-ph image of the week
>
> On Tue, Jul 6, 2010 at 9:20 AM, Ed Garcia <eppgarcia at gmail.com> wrote:
> > Wow! amazing ... how do you detect "sawtoothness"?  can you teach this at
> > the skillshare?  OSM genius ka talaga!
> >
> > Anyway, I take note of the sawtooth patterns between Lucena and Pagbilao
> > Quezon ... I have corrected this already but the sawtooth appears only on
> > higher zoom-out levels now.  Does this mean it is good as "done" now?  It
> > still appears on yoursawtooth_coastlines map though.
> >
> > ed
> >
> > On Tue, Jul 6, 2010 at 1:04 AM, Eugene Alvin Villar <seav80 at gmail.com>
> > wrote:
> >>
> >> HI guys,
> >>
> >> Here's an *initial* webmap showing where the jagged coastlines are as of
> >> July 3:
> >> http://forge.codedgraphic.com/osm/sawtooth_coastlines/
> >>
> >> The larger the circle, the more jagged steps there are to clean up.
> >>
> >> Sorry, there's no link going to Potlatch or JOSM/Merkaartor. I'll add
> that
> >> up when I learn more of OpenLayers. But for now, this will have to do.
> >>
> >> Enjoy!
> >>
> >> Eugene
> >>
> >> On Mon, Jul 5, 2010 at 9:30 AM, maning sambale
> >> <emmanuel.sambale at gmail.com> wrote:
> >>>
> >>> We missed the June target to to finish the 10 largest islands.
> >>>
> >>>
> http://wiki.openstreetmap.org/wiki/WikiProject_Philippines/Coastline_Corrections#Priorities
> >>>
> >>> That's OK.  All we need is to finish mainland Mindanao and we can set
> >>> our radar to the next 20 on the list.
> >>> We are also working on some webmap to visualize the "sawtooth".  More
> >>> on that when its ready.
> >>>
> >>>
> >>> On Sun, Jul 4, 2010 at 5:48 PM, maning sambale
> >>> <emmanuel.sambale at gmail.com> wrote:
> >>> > I can load it in my public dropbox.
> >>> >
> >>> > On Sun, Jul 4, 2010 at 2:23 PM, Eugene Alvin Villar <
> seav80 at gmail.com>
> >>> > wrote:
> >>> >> Hi guys,
> >>> >>
> >>> >> Once we are done with the large islands, the next step is to do the
> >>> >> smaller
> >>> >> islands. Ian Haylock has helpfully provided the PGS coastlines[1]
> for
> >>> >> the
> >>> >> Philippines last year[2] which he edited to combine ways. PGS itself
> >>> >> was
> >>> >> automatically generated by a software by analyzing the Landsat
> >>> >> imagery.
> >>> >> Unfortunately, Ian's file was hosted on a free file server and has
> now
> >>> >> expired but I think several people on the mailing list managed to
> >>> >> download
> >>> >> it.
> >>> >>
> >>> >> I tried opening the file last year in Merkaartor but my old laptop
> >>> >> couldn't
> >>> >> handle the data. Now that I have a 4GB-RAM laptop, loading the data
> >>> >> into
> >>> >> Merkaartor is very manageable. Using the PGS coastlines is much,
> much
> >>> >> easier
> >>> >> than tracing Landsat by hand. I tried this with Homonhon Island and
> >>> >> editing
> >>> >> is way faster than actually uploading it[3]. Hehehe. What I did was
> to
> >>> >> delete the SRTM-derived coastline[4] and replace it with the PGS
> >>> >> coastline[5].
> >>> >>
> >>> >> I think uploading the PGS coastlines is better for the smaller
> >>> >> islands. I'll
> >>> >> see what we can do to have the PGS coastlines (55MB) uploaded
> >>> >> somewhere.
> >>> >>
> >>> >> [1] http://wiki.openstreetmap.org/wiki/Prototype_Global_Shoreline
> >>> >> [2]
> >>> >>
> http://lists.openstreetmap.org/pipermail/talk-ph/2009-June/001071.html
> >>> >> [3] http://www.openstreetmap.org/browse/changeset/5129873
> >>> >> [4] http://www.openstreetmap.org/browse/way/4327906
> >>> >> [5] http://www.openstreetmap.org/browse/way/65592780
> >>> >>
> >>> >> Eugene
> >>> >>
> >>> >>
> >>> >> On Thu, Jun 17, 2010 at 8:20 PM, maning sambale
> >>> >> <emmanuel.sambale at gmail.com>
> >>> >> wrote:
> >>> >>>
> >>> >>> UPDATE. Only two islands from the top ten need some coasty
> coastline
> >>> >>> love.
> >>> >>>
> >>> >>>
> >>> >>>
> http://wiki.openstreetmap.org/wiki/WikiProject_Philippines/Coastline_Corrections
> >>> >>>
> >>> >>> Anyone working on Negros and Mainland Mindanao?
> >>> >>>
> >>> >>
> >>> >>
> >>> >
> >>> >
> >>> >
> >>> > --
> >>> > cheers,
> >>> > maning
> >>> > ------------------------------------------------------
> >>> > "Freedom is still the most radical idea of all" -N.Branden
> >>> > wiki: http://esambale.wikispaces.com/
> >>> > blog: http://epsg4253.wordpress.com/
> >>> > ------------------------------------------------------
> >>> >
> >>>
> >>>
> >>>
> >>> --
> >>> cheers,
> >>> maning
> >>> ------------------------------------------------------
> >>> "Freedom is still the most radical idea of all" -N.Branden
> >>> wiki: http://esambale.wikispaces.com/
> >>> blog: http://epsg4253.wordpress.com/
> >>> ------------------------------------------------------
> >>>
> >>> _______________________________________________
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> >>> talk-ph at openstreetmap.org
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> >>
> >>
> >>
> >> --
> >> http://vaes9.codedgraphic.com
> >>
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> >
> >
> >
> > --
> > website administrator:
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> > - reeflife.eppgarcia.com
> >
> > PADI Divemaster #491048
> >
>
>
>
> --
> cheers,
> maning
> ------------------------------------------------------
> "Freedom is still the most radical idea of all" -N.Branden
> wiki: http://esambale.wikispaces.com/
> blog: http://epsg4253.wordpress.com/
> ------------------------------------------------------
>
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