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Project from nad83 to wgs84 with '_itrf00' transformation?

  • 14 July 2021
  • 5 replies
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rmcgregor

Despite the fact that the nad83 and wgs84 datums are supposedly identical, there are several ways to get from one to the other and they result in different placement.

 

  • ESRI recommends this transformation: WGS_1984_(ITRF00)_To_NAD_1983
  • FME appears to use this one: nad_1983_to_wgs_1984_1

 

I am using AttributeReprojector on a dataset with several coordinate systems. Is it possible to indicate a specific geographic transformation for nad83 to wgs84 when using this?

 

Thank you,

 

Randy McGregor

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Best answer by virtualcitymatt 15 July 2021, 21:34

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virtualcitymatt
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I think you might want to look at the CSMapAttributeReprojector. ​http://docs.safe.com/fme/html/FME_Desktop_Documentation/FME_Transformers/Transformers/csmapattributereprojector.htm

It should alow you to specify a transformation ​

R
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I think you might want to look at the CSMapAttributeReprojector. ​http://docs.safe.com/fme/html/FME_Desktop_Documentation/FME_Transformers/Transformers/csmapattributereprojector.htm

It should alow you to specify a transformation ​

Thanks! I will take a look.

R
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Thanks! I will take a look.

The problem is that I have more than one datum in the input file, so if I just pick one transformation, I think it will use it on all the input coordinate systems whether or not it's appropriate. Wait, I just realized. I can create vertices for each datum, then run this for each datum, entering the appropriate transformation. That should work. Thanks.

R
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Thanks! I will take a look.

I have 2 accounts and this one can't set this as the right answer. I'll do that as soon as I scare up the password for the 'other Randy.' Thank you!

rmcgregor

Thanks! I will take a look.

Just FYI, CSMapAttributeReprojector does NOT have this transformation: WGS_1984_(ITRF00)_To_NAD_1983

 

I think FME is operating under the false belief that nad83 and wgs84 are identical and the datum conversion is not important. It is actually very important, because different geographic transformations put features in a visibly different location - Usually about 3 feet, but that's enough to cause trouble.

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