[talk-au] National borders (was: import of state borders?)

[Ian Sergeant]

Hi,

If I understand correctly,  the differences should only correspond to
the amount that our coastline differs from the low water mark?  Are we
missing parts of the true coastline, is our coastline just inaccurate
do you think?

I'd be surprised if there was any definitive low water mark data for
the entire coastline.

Should we start with a simpler section, like NSW?

Ian.

On 12 September 2012 23:04, Michael Krämer <ohrosm at gmail.com> wrote:
> Hi,
>
> 2012/8/31 Michael Krämer <ohrosm at gmail.com>
>>
>> 2012/8/31 Ian Sergeant <inas66+osm at gmail.com>
>>>
>>>
>>> Well, I think the baseline is defined here..
>>>
>>> http://www.comlaw.gov.au/Details/F2006L00525
>>>
>>> I don't think we have any issues using those facts as a source.
>>
>>
>> That looks great, combining this with the coastline should work. The
>> coastline can be either drawn via osmosis from a planet extract or perhaps
>> also from OverpassAPI. But I guess we'll have to generate all those line
>> segments in QGIS to get the coordinate systems right.
>
>
> A quick update from my side on this: I'm afraid it's not as straightforward
> as I had assumed...
>
> I managed to generate an osm file from the points given in the proclamation
> [1]. This gives the straight pieces of the baseline. But the problem is that
> the coastline doesn't really give the right baseline for the rest (high vs.
> low water mark). When I checked briefly I came across some pronounced
> differences for example in the gulf of carpentaria. I guess it will be the
> same along the Great Barrier Reef.
>
> So we would have to do some guesswork to combine coastline and straight
> segements.
>
> BTW, it's very likely not a projection issue. I made sure by doing a check
> of my calculations against the data Geoscience Australia provides.
>
> Michael
>
> -------
> [1] https://dl.dropbox.com/u/1222615/baseline.osm