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I posted a thread today describing a shift in some of the NRC data (not all). Apparently, this shift has to do with conversion between Geographic coordinates, latitude and longitude and Transverse Mercator Grid coordinates. Can someone please provide a guide on how to do this transformation in ArcGIS? I would like to transform that data to either Clarke_1866_Lambert_Conformal_Conic or GCS_WGS_1984.

Source Data Coordinate System:

GCS_WGS_1984
Angular Unit: Degree (0.017453292519943299)
Prime Meridian: Greenwich (0.000000000000000000)
Datum: D_WGS_1984
Spheroid: WGS_1984
Semimajor Axis: 6378137.000000000000000000
Semiminor Axis: 6356752.314245179300000000
Inverse Flattening: 298.257223563000030000
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4  
800 meters is too much for a datum difference--definitely between NAD83 and WGS84, and also between NAD27 and WGS84. If you did download the LCC data (in e00 format), is the GCS listed as Clarke 1866? Ugh. That's the default spheroid used if a datum isn't specific when using ArcInfo workstation. The data itself could be NAD27- or NAD83- or WGS84-based. But even if the datum was misdefined, 800 m is a more than I normally see. –  mkennedy Dec 16 '10 at 17:36
    
thanks. will give it a try. –  Jakub Dec 16 '10 at 17:41
    
I redownloaded e00 instead of shapefile. Shift is the same. The coverage Projection is as follows: Projection GEOGRAPHIC Datum NAD83 Zunits NO Units DD Spheroid GRS1980 Xshift 0.0000000000 Yshift 0.0000000000 –  Jakub Dec 16 '10 at 19:54
    
when editing: to keep linewrap intact, highlight the code block and press [ctrl-k] –  matt wilkie Dec 16 '10 at 23:19

1 Answer 1

up vote 9 down vote accepted

Responding to the question in the subject line and ignoring the body, please see About geographic transformations and how to choose the right one. The quick list:

  1. NAD_1983_To_WGS_1984_1 - for the entire North American continent.
  2. NAD_1983_To_WGS_1984_2 - for the Aleutian islands.
  3. NAD_1983_To_WGS_1984_3 - for Hawai'i.
  4. NAD_1983_To_WGS_1984_4 - superseded by _5; this transformation method should no longer be used!
  5. NAD_1983_To_WGS_1984_5 - for the 48 contiguous United States.
  6. NAD_1983_To_WGS_1984_6 - for the Canadian province of Quebec.
  7. NAD_1983_To_WGS_1984_7 - for the Canadian province of Saskatchewan.
  8. NAD_1983_To_WGS_1984_8 - for the Canadian province of Alberta.

Note that geographic transformations work in either direction. For example, the transformation listed as NAD_1983_To_WGS_1984_5 transforms from NAD 1983 to WGS 1984, as well as from WGS 1984 to NAD 1983.

Map of North American datum transformations (pic from Does Re-Projecting an ESRI ShapeFile only update the content of the .prj file?)

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Thanks Matt. This a nice graphical guide! I received a reply from NRC in regards to my data shift. It appears I was doing things correctly and the shift is within tolerance (800m) which according to Geogratis falls well within the horizontal accuracy of the data (1000m for 1:1,000,000) –  Jakub Dec 17 '10 at 0:50
    
Oh yes. And this is of course the answer. I posted the actual reply from NRC in regards to the shift in my previous post if anyone's interested. gis.stackexchange.com/questions/4479/… –  Jakub Dec 17 '10 at 1:18

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