[talk-ph] Fwd: RFC: importing Palawan roads

Sat Jun 6 04:49:44 BST 2009

I was about to ask you to ask them how they compiled their data. It
obviously wasn't traced over Google Earth nor taken using GPS tracks. I
think Rally might have guessed their method correctly.

On Sat, Jun 6, 2009 at 11:26 AM, maning sambale
<emmanuel.sambale at gmail.com>wrote:

> ---------- Forwarded message ----------
> From: Rally de Leon <ralleon at gmail.com>
> Date: Fri, Jun 5, 2009 at 9:36 PM
> Subject: Re: [talk-ph] RFC: importing Palawan roads
> To: maning sambale <emmanuel.sambale at gmail.com>
>
>
> Doing a quick check on proportions and shapes of different tracks from
> different portion of the map, I think the data supplied is trash. :-(
>
> I've seen shape files very much like this (like the one I obtained
> from Taytay Assessor) that was just traced over TAX MAPPING paper
> sheets (purely based on shape guestimation and visual
> ratio-and-proportion) then converted then to autocad drawings. I've
> seen them how they draw the lot shapes on paper (during the time
> nagtatambay ako sa assessor). It's doable if you know where to chop
> the areas (eg. per subdivision or per purok), then convert it back to
> raster image, then georectify that image (for every area) which will
> need actual gps waypoints, then trace your vector lines over the
> raster layer. But what's the point? we are talking of the whole
> palawan.The purpose of this data is just for assessment and for
> assigning PIN codes on the tax declaration, not for navigation nor for
> making proportionally correct paper map.
>
> I highly doubt that the data came from actual field survey. Because
> I've traced Namria topo maps before (in Luzon datum), and they were
> proportionally correct when I translated them to WGS84. My old
> personal garmin maps were made this way with fairly high degree in
> accuracy. But in this case, the shp file have wrong proportions,
> different shapes, different angles, a lot of extraneous lines and
> streets (that doesn't make sense), really bad. I tried Luzon-Mean,
> Luzon-Philippines, Luzon-Mindanao (all failed), so I tried to cheat by
> just dragging them over google satellite image, still failed, won't
> fit. No wonder you can't make it fit using all available datum, hehe.
> nadaya yata tayo dun. If we are lucky enough to have one subdivision
> fit the roads of a satellite image (yahoo or google), the adjacent
> subdivision won't (as i've tried it since this was really easy to do
> in trackmaker pro). In my experience, even those subdivisions as far
> as 500meters from your reference tracklog should still fit the
> satellite image with your extended vector traces; in this case, even
> the neighboring streets a few blocks away doesn't.
>
> So, we'll surely get in trouble or lose good reputation for uploading
> bad data, hehe. I suggest we just recruit gps-tracker volunteers in
> any of the streets in palawan (where there are good hi-res satellite
> images), and lets do it the old fashion way.
>
> Call back the source of this data and ask him to confess (if they
> really made that survey). kung ayaw umamin, i-torture natin ;-D
>
>
> On Fri, Jun 5, 2009 at 6:17 PM, maning sambale
> <emmanuel.sambale at gmail.com> wrote:
> >
> > I tried every projection parameters I can think of pero may shift pa
> > rin, anyway the shift is systematic so moving the whole data to fit
> > existing OSM roads, should be straightforward.
> >
> > Here's the data, around 7 MB:
> > http://esambale.wikispaces.com/file/view/palawan_roads.zip
> >
> > Tirahin mo sya!
> >
> > On Fri, Jun 5, 2009 at 6:01 PM, Rally de Leon<ralleon at gmail.com> wrote:
> > > can you send me a copy of this palawan tracks? how big? i'm sure you
> already
> > > have your methods of converting to wgs84.
> > >
> > > but let me see what i can do (para meron naman akong mapaglibangan this
> > > weekend). don't worry, i'm not going to trace over googleearth. (lets
> just
> > > compare notes later) :-)
> > >
> > > i'm just going to try if it's as easy as shifting the entire thing on
> the
> > > built-in datum-shifter of GPS trackmaker, if it works and passed our
> > > counterchecks,
> > > then the data goes to JOSM for additional validations, edits and
> tagging.
> > >
> > > else if it's not that easy, maybe we can use a method of shifting
> arbitrary
> > > control points. (most likely, palawan is on Zone 2 of Luzon Datum, then
> > > convert to WGS84) (practically, all main Luzon island is on Zone 3 -
> the one
> > > used by surveyors). The alignment of these "luzon-datum tracks" to the
> > > "computed WGS84 control points" can be done entirely within JOSM by
> just
> > > dragging the entire tracks. We have many ways to check the accuracy
> > > afterwards. medyo barok (as we will use graphical method - JOSM's is
> very
> > > good at this), but it may work without the need to for mathematical
> > > conversions and without the need to rely on googleearth alignments.
> > >
> > > On Fri, Jun 5, 2009 at 2:51 PM, maning sambale <
> emmanuel.sambale at gmail.com>
> > > wrote:
> > >>
> > >> > There is no online map we can compare the traces to to see how
> accurate
> > >> I'm doing it when I got this message. :)
> > >>
> > >> See for yourself over GEarth (blue is OSM, red is the road data).
> > >> http://farm4.static.flickr.com/3566/3596753363_51c00bb5f3_o.jpg
> > >>
> > >> Notice the shift?
> > >>
> > >> (copyright image of DigitalGlobe and Google included to abide by it's
> > >> Terms of Use) :)
> > >>
> > >>
> > >> On Fri, Jun 5, 2009 at 2:18 PM, Andre Marcelo-Tanner<
> andre at enthropia.com>
> > >> wrote:
> > >> > There is no online map we can compare the traces to to see how
> accurate
> > >> > it is?
> > >> >
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> > >>
> > >>
> > >>
> > >> --
> > >> 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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> > >
> >
> >
> >
> > --
> > 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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