creating custom co-ordinate system.

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chris
I've been looking into creating my own custom co-ordinate system.

this is to hopefully fix my rotation issues on export, but also so i can get the same co-ordinates to work over different software.

I'd like to take GDA94 / MGA zone 55, and give it a false northing and false easting. that will transform the center of the model x, y = 0,0 with the height keep at real world.

I've found the epsg.xml file.

<cs id="28355" desc="GDA94 / MGA zone 55" params="+proj=utm +zone=55 +south +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs"/>

my idea is to copy this line and edit it to be a custom setting.

Is this the line i should be editing to get an offset?
"+towgs84=0,0,0,0,0,0,0"

what i'm not sure about is why there are 7 numbers rather than 6 if it was false northting xyz, false easting xyz.

or is it something else i need to put in there to adjust it.
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    tomasb
    those strings in xml def file are proj.4 library coordinate systems strings. and towgs= define helmert transformation parameters. there should be som authority that provides these numbers. btw you should verify if your XY Coordinates are not swapped
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    Geoinfodoo

    tomasb

    Hi. I know its been long time of this post but I face same problem - how to create my own coordinate system. What do you mean it should be some authority that provide this numbers?

    Is there any reference how to create custom coord system?

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    Ondrej Trhan CR

    Hi Geoinfodoo, regarding to authority, it should be some Geodesy, Cartography and Cadastre Authority for your country.

    Do you want to change some of the used coordinate systems or you have your own coordinates? Is it possible to use it as local?

    For example I add into local.XML one local coordinate system using feet:

    <CoordinateSystems authority="Local">
        <cs id="1" desc="Euclidean" params="+proj=geocent +ellps=WGS84 +no_defs" />
        <cs id="2" desc="Laboratory" params="+proj=geocent +ellps=WGS84 +units=mm +no_defs" />
        <cs id="3" desc="Feet" params="+proj=geocent +ellps=WGS84 +units=us-ft +no_defs" />
    </CoordinateSystems>

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