Talk:North American Datum

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Eccentricity Squared[edit]

The article lists eccentricity squared for NAD83 as 0.006694300229. NAD83 is based on GRS80, and this article states that its eccentricity squared is 0.00669438002290. It appears that the article is missing the 8 between "43" and "00"? But I wasn't sure if the source is accurate or if NAD83 is definitely the same as GRS80 so I didn't want to change it. -- – Zawersh 17:03, 28 May 2008 (UTC)

"Datum" Grammar[edit]

The plural of the word "datum" is "data", so it appears odd to see a reference to multiple datums in the article. However, this is not the only place I've seen such usage, so I'm wondering if datums is a commonly accepted term in geography? Sterling Gillette (talk) 17:40, 17 October 2008 (UTC)

According to Merriam-Webster, something "as a basis for reasoning or inference" plural is data, while something "used as a basis for calculating or measuring" is datums. --skew-t (talk) 00:27, 29 December 2008 (UTC)

Irregularity in notation[edit]

I came to this page to find whether I should write NAD83, NAD-83 or NAD 83 and you use all three. Which is right? 20 November 2008 —Preceding unsigned comment added by 205.200.189.2 (talk) 20:38, 20 November 2008 (UTC)

GRS 80[edit]

EPSG database (cod = EPSG::7019) gives a value of 298.257222101 for the inverse flattening and notes, “Inverse flattening is derived from geocentric gravitational constant GM = 3986005e8 m*m*m/s/s; dynamic form factor J2 = 108263e8 and Earth's angular velocity = 7292115e-11 rad/s.” Flattening is not part of the GRS 80 definition; it, too, is derived from those constants. This is confirmed from other sources I checked.

That might argue for different terminology in the footnote, but consider also that it is confusing for the two tables to use different notation. Whatever we ultimately settle on ought to use unified symbols. Strebe (talk) 00:44, 8 January 2011 (UTC)

Why have two tables at all? Just explain each definition in a paragraph. As I just added, the NAD27 definition needs a bit of additional explanation too. Tim Zukas (talk) 20:42, 8 January 2011 (UTC)
Note that the GRS80 article gives the calculation of its flattening. Tim Zukas (talk) 20:45, 8 January 2011 (UTC)
I agree a single table in a section dedicated to the definitions would be helpful. Strebe (talk) 22:56, 8 January 2011 (UTC)

Dane Erickson paper in references[edit]

This may have been excellent information in 1994, but there are some things outdated in it. As shown in External Links, NGS offers on-line NADCON computations and free download of an exectutable, rather than selling disks. The bug given much discussion has been fixed for so long that a mere reference to serious bug in 1994 version would be sufficient.

Most importantly, is the information about FCC methods still current? —Preceding unsigned comment added by BillHart93 (talkcontribs) 15:13, 7 May 2011 (UTC)

404 error[edit]

Here is a page in the external refs which gives a 404 error:

NOAA-NGS-coordinates CORS-active network - explanation of NAD 83(2011) epoch 2010.00

I found a page: http://www.ngs.noaa.gov/CORS/coords.shtml

But, I do not know if this is the same page.

John W. Nicholson (talk) 02:54, 4 April 2013 (UTC)

I believe that is an appropriate page and recommend you change the link. BillHart93 (talk) 14:13, 4 April 2013 (UTC)

Explanations for casual readers[edit]

With reference to this edit: The North American Datum is the Geodetic data system now used to define the integrated geodetic network of maps in North America. The NAD systems provide a indexing framework and reference.

I do not find “Geodetic data system” to be explanatory. It is unlikely to mean anything more to a casual reader than “datum” is. It obscures the term “datum” which is used throughout the article. Nor is that explanation commonly used in texts. Readers should just follow the link, though I have added a short explanation that might suffice. Also, using integrated geodetic network of maps as a description for a link to Geodesy is just wrong. I deleted The NAD systems provide a indexing framework and reference because I also did not find that likely to mean anything useful to a casual reader, and merely vague and puzzling for a knowledgeable reader.

I have made several other changes, hopefully viewed as improvements. Strebe (talk) 23:42, 13 October 2013 (UTC)

85th meridian?[edit]

Meades ranch, with a longitude of more than 98 and a half degrees west, is rather far from the 85th meridian. Can someone explain the connection? Is it a typo?

The linked JSTOR article is not free and the preview does not cover this point. A Google search for items more than a year old containing Meades Ranch 85th meridian finds only the wikipedia article. Since then a huge number of sites appear to have quoted it, but I'm wondering if it is wrong. BillHart93 (talk) 19:40, 14 October 2013 (UTC)

This publication is by the Coast and Geodetic Survey, who established the datum http://docs.lib.noaa.gov/rescue/cgs_specpubs/QB275U35no701921.pdf See Figure 1 for a map of the triangulation work and other detailed figures that include Meades Ranch as part of the 98th meridian survey.

If no one posts a counter-argument, I'm going to change 85th to 98th. BillHart93 (talk) 16:41, 15 October 2013 (UTC)

Your analysis looks right to me. We can fix it if we later discover otherwise. There seems to be a copy of Schoewe’s document available from the National Park Service, but the government shutdown leaves the link broken. Google’s cached copy is a mess. Strebe (talk) 19:41, 15 October 2013 (UTC)