Question

Problems creating a new coordinate system

  • 9 January 2018
  • 3 replies
  • 3 views

I need to change a definition of a foot from Survey feet to International feet in the NAD83 Hawaii SPC 3Feet (HI83-3F) coordinate system in FME. I used the description in https://knowledge.safe.com/questions/41372/how-do-i-create-a-custom-coordinate-system.html and the tool at http://fme.ly/coordsys.

I am using FME 2016.1.0.1 (20160516 - Build 16494)

When I use either Reprojector or CsmapReprojector to convert from UTM with NAD83 datum, Zone 4, Meter to my new coordinate system I am getting the same coordinate as I get when I convert to HI83-3F.

I need to verify that the new coordinate system is using 0.3048 as the meters to feet conversion value.


3 replies

Badge +11

Hi @mjbetts, have you also viewed FME Workbench documentation for Custom Coordinate Systems?

 

https://docs.safe.com/fme/html/FME_Desktop_Documentation/FME_Workbench/Workbench/coordinate_sys_custom_about.htm

With respect to your query to verify if the coordsys is using 0.3048 – what is currently set for UNIT in your coordinate system definition?

 

According to this page, FOOT = US survey foot = 0.30480060960121920243.

 

Edit: IFOOT = international foot = 0.3048 <-- That might be the unit you are looking for.

If you are still having issues with the reprojection, attaching the coordsys definition here for the FME Community to investigate will be helpful.

IFOOT is what is in the file but based upon my testing I question that 0.3048 is being used. I have used Oracle's re projection engine using a SRID that is in Survey feet and I get the same answer as FME for my IFOOT coordinate system

Attached is the zip file that http://fme.ly/coordsys produced.

fme-2e2f706c-1515533630279-30306.zip

Userlevel 2
Badge +17

Hi @mjbetts,

The difference between the two coordinate systems will only be about 3 inches.

I am attaching a definition for HI83-3IF and a workspace to compare a point in the middle of Oahu for you. The Survey Foot point should be about 0.25 feet below the International Foot point.

test-hi83-3if.fmw

fme-2e2f706c-1515537307417-3341.zip

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