[talk-ph] Admin Boundary and Coastline

maning sambale emmanuel.sambale at gmail.com
Fri May 20 05:15:48 BST 2011

On Fri, May 20, 2011 at 11:50 AM, Eugene Alvin Villar <seav80 at gmail.com> wrote:
> Hi Murlwe,
> I don't think that municipal/provincial waters should be clamped to
> the national waters.
> According to the UNCLOS, national waters are those that are within 12
> nautical miles (about 22km) from the coastline. According to the
> Philippine Fisheries Code of 1998, municipal waters are within 15
> kilometers of the coastline. In addition, there is yet no rule on how
> to deal with overlapping municipal waters.

According to the Fisheries Code:
Where two (2) municipalities are so situated on opposite shores that
there is less than thirty (30) kilometers of marine waters between
them, the third line shall be equally distant from the opposite shore
of the respective municipalities.

This can be easily done with a GIS buffer operation, but I don't find
any real need for osm to do that.  You can of course download the osm
data and create your preferred boundary within a GIS app.

> I couldn't find a law stating anything about provincial waters, but I
> assume they encompass their municipalities' waters. Same with barangay
> waters.
> So the idea is to mark admin boundaries of barangays,
> municipalities/cities and provinces as just the land portions for now.
> This includes islands.
This is a touchy issue (politically), so for now, I agree with using
coastlines as part of the admin boundary. Plus, it is easier to
maintain the data since when we move the the coastline, the admin
boundary in relation to the coastline move as well.

Although I have different opinion with "clamping" boundary relations to rivers.

> If the concern is that you want to signify that places/landmarks of an
> LGU are within its boundaries in GIS terms, then the GIS app need to
> support boundaries that are composed of multiple polygons. For
> example, Caloocan City is composed of 2 disjoint territories
> <http://www.openstreetmap.org/?relation=273242>. To say that a street
> or POI is within Caloocan, the GIS app needs to support multiple
> polygons.

I think postgis can do this.

> Same thing goes currently with LGUs that have islands. The admin
> boundaries currently include islands as multipolygons. For example,
> Romblon, whose boundaries are currently clamped to the coastlines of
> all of its constituent islands:
> <http://www.openstreetmap.org/?relation=1506343>.
> Eugene
> On Fri, May 20, 2011 at 10:27 AM, Marloue Pidor
> <murlwe at mail2engineer.com> wrote:
>> Hi Eugene, I find it easier if the Barangay boundaries be extendend to the
>> City/Municipal boundary, City/Municipal boundary be extended to the
>> Provincial boundary, Provincial boundary to the Country boundary. This is
>> just a suggestion for the coastal areas as you said to map out the exact
>> municipal and provincial waters. If you notice here,
>> http://osm.org/go/4sY75GPk-- the admin boundaries are clamped to the
>> shoreline and creating the same to the island when we can include those
>> island to the municipal boundary. I'm suggesting this because on a GIS point
>> of view, it is easier to look for places when it is placed inside
>> boundaries.
>> murlwe
>> <-----Original Message----->
>> From: Eugene Alvin Villar [seav80 at gmail.com]
>>>Sent: 5/19/2011 10:13:33 PM
>>>To: murlwe at mail2engineer.com
>>>Subject: Re: [talk-ph] Admin Boundary and Coastline
>>>There's no real need. The idea is that in the future we would be able
>>>to map out the exact municipal and provincial waters. But until then,
>>>making the admin boundaries just tackle land for the moment is
>>>manageable since data is much more readily available.
>>>Please reply if you have other suggestions. :)
>>>On Thu, May 19, 2011 at 8:23 PM, Marloue Pidor <murlwe at mail2engineer.com>
>>>> Is there a need to clamp the admin boundaries to the coastline?
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