[Imports] Boundary of Tonga

[Stephen V. Mather]

Is the baseline definition then just a convex hull of the geometry?  That's not hard to calculate.

Stephen Mather
Geographic Information Systems (GIS) Manager
(216) 635-3243
svm at clevelandmetroparks.com
clevelandmetroparks.com





-----Original Message-----
From: Michael Krämer [mailto:ohrosm at googlemail.com] 
Sent: Tuesday, May 15, 2012 3:54 PM
To: imports at openstreetmap.org
Subject: Re: [Imports] Boundary of Tonga

Hi,

as my first reply didn't go to the list but directly to Frederik here a 
second try:

Am 15.05.2012 16:50, schrieb Frederik Ramm:
> I noticed that of all 193 UN member states, there's only one for which
> we don't have international borders in our database (instead, a node
> tagged place=country). That country is Tonga in the South Pacific.
Yes, there's quite a bit left to map in the South Pacific.

> I have taken our existing Tonga coastline and computed a 12nm buffer
> around that (after having read on the CIA world factbook that they have
> a 12nm territorial waters claim), and prepared the following file with a
> boundary relation that we could use to replace the country node:
Well, this is probably the best we can get for the time being. In a 
perfect world we wouldn't use the coastline but the baseline. The 
baseline definiton ([1], 5+6) closes bays by straight lines which makes 
a difference given the shape of the islands.

But manually deriving the baseline using Bing imagery would be a rather 
complex task. So unless there's a decent way of doing this by some fancy 
software package I think there's no way of getting the basline.

So I think using the coastline is fine. But I would suggest to add a 
note to the data somehow along the lines of "only approximate, base on 
coastline".

> http://www.remote.org/frederik/tmp/proposed_tonga_boundary.osm
After looking at the data I think you missed some islands that have 
quite an impact to the border. I did some checks with Wikipedia (also 
adding a few names) and found the follwing ones (with Way ID)
?Ata (22383999)
Toku (22390574)
Fonualei (22390195)
So if you don't mind, I would ask you to add these.

> I'm not 100% sure if my reasoning is correct; there is the case of the
> Minerva reef which lies about 200km to the SW of Tonga and I read that
> Tonga lays claim to that - but, as far as I understand, only EEC claim
> and not territorial, so I guess it is correct to not include it in the
> country boundary.

I agree. From what I understood the reef is submerged so I don't think 
it's possible to establish a territorial claim. But I'm also not 
completely sure about this.

> I'm not normally in favour of doing imports but seeing that Tonga is
> really the "odd one out" in the list of countries, maybe it is worth the
> effort to fix that.
I think that an import makes perfectly sense for boundaries, especially 
maritime borders. They hardly can be mapped on the ground.

Michael

[1] 
http://www.un.org/depts/los/LEGISLATIONANDTREATIES/PDFFILES/TON_1989_Act.pdf

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