On Sun, 18 Jul 2010 09:49:41 +1000
Liz <[email protected]> wrote:

> The original Murray River trace was either made by swampwallaby using vmap or 
> by a few of us tracing from Landsat.
> The only surveyed points then would have been bridges and bridge piers.
> 
> So the admin boundary, which is definitely not the wet part of the river, is 
> more accurate overall
> 
> Some can now be seen on Nearmap, and this is enough resolution to split the 
> river from the admin boundary.
> This might be best done by drawing in riverbanks and making areas of the 
> river.

This is my point exactly and I was only using the Murray River as an example of 
where the admin boundary does not correspond with what's on the ground.

When the only data is the admin boundary use it to define rivers etc when known 
or in conjunction with landsat or other low res images.

When there is hires imagery such as Nearmap, or surveyed data there is no 
justification for making an admin boundary into a road/river/railway line.

The admin boundaries don't get moved with road/railway realignment and 
therefore without change from the original source we should not be moving them. 
 So if they are not connected to railways/roads etc then errors will not be 
introduced.



-- 
Cheers
Ross


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