[Manifold-l] Custom datums

[Linley]

Hi all,

Posted this at georeference, but not a single reply. Hope someone can help. Sorry for the long post:-

My first attempt at a custom datum & projection, Will be pleased if someone can cast an expert eye over the following, as I doubt that I really know what I am doing! Loads into Manifold fine, but two worries - on my home turf, I can check that data received makes sense, but this is new territory. Also understand Manifold doesn't consider the 7th (scale) parameter in the transformation (so left it out). Is this correct, & what affect does it have on accuracy?

<xml>
<datum>
<name>Fiji Geodetic Datum 1986</name>
<ellipsoid>WGS72</ellipsoid>
<centerX>35.17277931989845 </centerX>
<centerY>-136.5712601696053 </centerY>
<centerZ>36.96429263506973m </centerZ>
<rotationX>-1.37101925914775</rotationX>
<rotationY>0.841968640179647</rotationY>
<rotationZ>4.718005596536956</rotationZ>
</datum>
</xml>

<xml>
<preset>
<name>Fiji Map Grid</name>
<category>National Grids*Fiji</category>
<system>Transverse Mercator</system>
<datum>Fiji Geodetic Datum 1986</datum>
<centerLat>17</centerLat>
<centerLon>178.75</centerLon>
<scaleX>0.9998548</scaleX>
<scaleY>0.9998548</scaleY>
<falseEasting>2000000</falseEasting>
<falseNorthing>4000000</falseNorthing>
</preset>
</xml>

Available data was

Fiji Geodetic Datum 1986 (from WGS84)

Ox: -1.37101925914775" 
Oy: 0.841968640179647" 
Oz: 4.718005596536956" 
dx: 35.17277931989845m 
dy: -136.5712601696053m 
dz: 36.96429263506973m 
m: 1.537002362494988ppm 

Fiji Map Grid, FMG:
Projection: Transverse Mercator 
Datum: Fiji Geodetic Datum 1986 
Spheroid: WGS72 
Longitude: 178045'00"E 
Latitude: 17000'00"S 
Scale Factor: 0.9998548 
False Easting: 2,000,000 
False Northing: 4,000,000

Can't vouch for any of this. MTIA
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