[worldKit-dev] use of GDA94 in world kit

[Matt McClelland]

Thanks Mikel

OK my head is about to explode - I have not done this much math since ....
well, every really.

I found an article on redearn formula that is used to convert between GDA9A
Northing and easting to LAT and LONGS.  I then wrote and and PHP file to
convert "BBOX=" values to northings and eastings to request the correct
file.  And it seems to work well.  (there is a problem with zooming west of
King island - as the server does not seem to allow request outside of zone
55 - so don't go west of king Island.

The script outputs a KML file for google earth to create an overlay - seems
to work well.  But for this to work with world kit I think I need to pass an
image not a xml file with the location of the image.  So next step is to
pull out the PHP book again and learn how to pass and image file - unless
you have a better idea. (I would rather not have to load the image into the
server and then send it again - this would be very slow)

The script still have a little bit of tweeking you may notice the top of the
map is stretched out a bit.

I have attached the KML file to play with  --  remember to zoom right into
Tasmania Australia (that is under downunder)

Matt  :)



On 6/14/06, Mikel Maron <mikel_maron at yahoo.com> wrote:
>
> Hey Matt
>
> GDA94 [Geocentric Datum of Australia 1994 (GDA94)]   is a UTM projection
> .. chosen since it will produce less distorted images over Australia than
> unprojected lat/long imagery.
>
> I am not aware of an easy way either, but am aware of A way.
> http://brainoff.com/weblog/2006/06/02/1157 describes a bit of what we did
> to reproject imagery of Indonesia into unprojected lat/long. It may have
> enough pointers to get going. You will have to have a "world file" for this
> image prepared.
>
> Let me know how it goes, we can hash it out.
>
> Mikel
>
> ----- Original Message ----
> From: Matt McClelland
> To: Discussion of worldKit use and development
> Sent: Friday, June 9, 2006 8:13:53 PM
> Subject: [worldKit-dev] use of GDA94 in world kit
>
> one data source that I am wanting to use with worldkit is in a GDA94
> system (as apposed to normal lat and longs used in worldkit)  I really don't
> understand why there are different systems, but hay.
>
> I am not aware of any easy way to convert between GDA94 and lat long, so I
> am a bit stuck in how to intergrate this into world kit.
>
> Here is a url with a sample image
>
>
> http://www.thelist.tas.gov.au/listmap/servlet/listmapGetMap?minx=440000&miny=5371500&maxx=446000&maxy=5376000&iwidth=1600&iheight=1600&layers=26,194,22,19,18,2,197,196,39,40,198,27,28,195,20,202,10,25&imageno=41&grid=true
>
> you can see the easting and northing figures in the minx miny (and maxx
> maxy)  (this map source is for the state of tasmania in Australia and is
> protected under copyright, ra ra ra)
>
> Any ideas???
>
> thanks
>
> Matt  :)
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