Question

How to improve re-projection accuracy

P

Hi Guys, I wonder if anybody can point me i the right direction .... I'm using 2021.0.2 desktop on windows.

I have a workbench, it loads an oracle table, I add 2 new fields, and the a transformer ProjAttributeReprojector, this takes an Irish Grid TM73 [epsg: 29903] and reprojects to ITM (IRENET95 / Irish Transverse Mercator [EPSG:2157]).. Then I use the Transformer - VertexCreater to create a point layer which is in ITM (IRENET95 / Irish Transverse Mercator).

When I analyze this layer all looks good except the location of the point and the new fields containg the x,y reprojected coordinates are incorrect on average 30cm difference to what the should be using reference data supplied by the vendor, similar reprojections performed in Arcgis Pro and ArcMap and using the online tool supplied by the National Mapping Agency to perform coordinate conversion. The verndor, ArcGis Pro, Arcmap and Online tool are all the same value.

So my question is - How do I improve the accuracy? is it possible. Is theresomething I have to tweak ?

Its critical that I do not move data to an incorrect location and 10-30cm is outside my acceptable scope.

Regards

Paulg

 

3 replies

nielsgerrits
Rank
Userlevel 6
Badge +32

I'm no expert in this field but if you use the EsriReprojector you should end up with the same results as when done with ArcGIS Pro / ArcMap?

P

I'm no expert in this field but if you use the EsriReprojector you should end up with the same results as when done with ArcGIS Pro / ArcMap?

Thanks .... I'll take a look ...... and report back

 

cheers

P

An update .. got it working with Reprojector and using the CoordinateSystemSetter to define the input projection. This worked a charm - slight variation but minor. I couldnt get teh ESRIReprojector working with a multiple step transform - I did follow the instructiosn and copied/moved evrything into the FME folders butit never gave me teh capability of a drop down list for Geographic Transformations. I did tinker with 'create custom transformation' but the help wasnt clear enough for me... So I've stuck with Reprojector and all is good so far. Thanks for the help

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