[wellylug] Topo data

[Michael Field]

I've been here, done that.

The best source of pure DEM data I have found is from
GeographX digital mapping. The data set has been
derived by sampling the LINZ topomap database at 25m
intervals. They have a free 250m DEM, and sample
datasets of the 25m to test with.

I purchased the Cook (Wellington) area tile in ascii
format and then converted it to work with a large DEM
dataset viewer ('soar' - 
http://www.gvu.gatech.edu/people/peter.lindstrom/software/soar/
-  Open source) and a subset to work with SSS (A slope
soaring Simulator -
http://www.rowlhouse.co.uk/sss/index.html - Open
source too). You pay by the square KM in the tile.

You can combine the dataset with back and white high
-rez Aerial Photos from
http://www.linz.govt.nz/rcs/linz/pub/web/root/core/Topography/AerialAndOrthophotos/OrthophotoIndex/apR27/index.jsp
if you want to, be warned - you need a lot of memory
to GIMP the images!

Mike

PS. Here is the reply that I received when I asked
about reditributing a limited subset:

From: 	Roger Smith <roger at geographx.co.nz>
To: 	Michael Field <mfield at concepts.co.nz>
Subject: 	Re: DEM usage.
Date: 	Tue, 22 Apr 2003 09:36:55 +1200	
Hi Mike
Thanks for the inquiry. Our licencing pretty much
allows you to do anything EXCEPT on-supply the
data to a third party. However there is no issue if
you re-process the data first, especially if it is a
small subset such as you are contemplating

Kind regards

Roger Smith

GeographX digital mapping
www.geographx.co.nz
PO Box 28100, Wellington, New Zealand.
Tel: 04 473 2718 Mobile: 25 577 265
Email: roger at geographx.co.nz

 --- Wood Brent <pcreso at pcreso.com> wrote: > 
> --- "E.Chalaron" <e.chalaron at xtra.co.nz> wrote:
> > I understood that Landcare produced a very
> accurate DEM (~25 m) of all NZ? 
> > Am I wrong and if not how available is this ?
> 
> I have heard that also, but not seen it. Of all the
> CRI's, Landcare seems the
> one most interested in masking such work freely
> available. Most others are
> really trying to make as much money as possible from
> everything they do, which
> is pretty much the model the Govt has imposed on
> them.
> 
> The LINZ data is NOT a DEM. It is vector data
> representing topographic
> features, incl roads, rivers, etc. The elevation
> contour vector data included
> in this can be used to build pretty reasonable DEM's
> if required.
> 
> > I am not sure that any other countries has done
> that yet.... 25 m !!!!!!
> 
> It is a pretty great achievment if so. I'd like to
> know if that is 25m
> horizontal or vertical (or both). 
> 
> > 
> > > You might want to check that they are happy with
> their data being
> > > redistributed for free. I don't think they'd be
> too happy about that and it
> > > doesn't sound like their intention.
> > 
> 
> LINZ in currently running beta2 of their Topoonline
> web site, to allow anyone
> to download (for free) small areas of the same topo
> data. It woul be a major
> job to download the whole 12Gb piecemeal & merge
> them back into the original.
> 
> The issue IMHO is not LINZ being concerned, as my
> discussions suggest they are
> quite comfortable with the idea. It is the
> commercial data reformatters who
> make $$ from their added IP that we would be
> competing with, if anyone.
> 
> Cheers,
> 
>   Brent Wood
> 

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