# Map location question Zero point for NAD 83 **URL:** \ **Category:** Factual Questions\ **Created:** [November 26, 2018, 4:54pm UTC](https://boards.straightdope.com/t/map-location-question-zero-point-for-nad-83/825113 "2018-11-26T16:54:02Z")\ **Posts on this page:** 8\ **Page:** 2
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [November 29, 2018, 4:39am UTC](https://boards.straightdope.com/t/map-location-question-zero-point-for-nad-83/825113/21 "2018-11-29T04:39:23Z")
International Terrestrial Reference Frame or ITRF hit a limit of about 10 mm with a change about 1mm per year. But today a news story hit that will help improve that. FWIW, current science needs about ~1 mm of accuracy, but that isn’t possible under the current model that uses Newtonian Mechanics. With these new clocks they will be able to move to a Post-Newtonian model which will allow for a more accurate ITRF. > **[NIST atomic clocks now keep time well enough to improve models of Earth](https://phys.org/news/2018-11-nist-atomic-clocks-earth.html)** > > Experimental atomic clocks at the National Institute of Standards and Technology (NIST) have achieved three new performance records, now ticking precisely enough to not only improve timekeeping and navigation, but also detect faint signals from... ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [November 29, 2018, 9:14am UTC](https://boards.straightdope.com/t/map-location-question-zero-point-for-nad-83/825113/22 "2018-11-29T09:14:50Z")
Does it matter that when Victorian astronomers did their calculations, they got the position of the Prime Meridian wrong by 102.5 metres? > **[Here's why the Greenwich Prime Meridian is actually in the wrong place](http://theconversation.com/heres-why-the-greenwich-prime-meridian-is-actually-in-the-wrong-place-46302)** > > Modern GPS has revealed the line used to calculate map coordinates and time zones is in accurate. Whether that really matters is another question. ---
**Author:** ![JKellyMap](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jkellymap/32/15880_2.png) [@JKellyMap](https://boards.straightdope.com/u/JKellyMap)\ **Post date:** [November 30, 2018, 2:41pm UTC](https://boards.straightdope.com/t/map-location-question-zero-point-for-nad-83/825113/23 "2018-11-30T14:41:49Z")
> [@bob\_2](#): > > Does it matter that when Victorian astronomers did their calculations, they got the position of the Prime Meridian wrong by 102.5 metres? > > [Here’s why the Greenwich Prime Meridian is actually in the wrong place](http://theconversation.com/heres-why-the-greenwich-prime-meridian-is-actually-in-the-wrong-place-46302) Ha. As that article sort of mentions, on the most basic level it’s logically impossible to mess this up, because you can put the prime meridian wherever you damn well please! ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [November 30, 2018, 4:25pm UTC](https://boards.straightdope.com/t/map-location-question-zero-point-for-nad-83/825113/24 "2018-11-30T16:25:29Z")
> [@JKellyMap](#): > > Ha. As that article sort of mentions, on the most basic level it’s logically impossible to mess this up, because you can put the prime meridian wherever you damn well please! Yeah - but we got there first so you guys are stuck with it going through Greenwich…🙂 ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [November 30, 2018, 4:53pm UTC](https://boards.straightdope.com/t/map-location-question-zero-point-for-nad-83/825113/25 "2018-11-30T16:53:51Z")
> [@JKellyMap](#): > > Ha. As that article sort of mentions, on the most basic level it’s logically impossible to mess this up, because you can put the prime meridian wherever you damn well please! Totally true, but you can mess up the actual surveying and measuring, which is what the article was describing! Anyhow, the measurement in question has been superseded many times and experimental error is down to centimetres these days, if not better. ---
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [November 30, 2018, 5:27pm UTC](https://boards.straightdope.com/t/map-location-question-zero-point-for-nad-83/825113/26 "2018-11-30T17:27:52Z")
It is a hard problem, when they created the metric system the meter was intended to be an even division of the distance between the equator and the north pole. They spend _7 years_ trying to be as perfect as possible and still didn’t get an exactly correct number. ---
**Author:** ![Kron](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kron/32/12444_2.png) [@Kron](https://boards.straightdope.com/u/Kron)\ **Post date:** [November 30, 2018, 6:56pm UTC](https://boards.straightdope.com/t/map-location-question-zero-point-for-nad-83/825113/27 "2018-11-30T18:56:21Z")
> [@Pork\_Rind](#): > > I see various links that say there’s a difference of somewhere between 1 and 2 meters; close enough for the consumer. > > I get a huge laugh out of this statement though… > > … and I don’t really know why. I guess I like the image of some poor cartographer having to figure for drift and hoping that he or she can just retire before the number becomes significant. The USGS redefines NAD83 every so often. The current realization is NAD83 2011. In the next few years, there will be another redefinition- I don’t remember if it was to be 2020 or 2021. I’ll have to check. And of course, the drift is at different speeds and directions in different places- the last update had some serious changes in the west, along the active tectonic boundaries along the Pacific. I’m lucky, here in the middle of nowhere the year-to-year changes are very minor. ---
**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\ **Post date:** [November 30, 2018, 7:02pm UTC](https://boards.straightdope.com/t/map-location-question-zero-point-for-nad-83/825113/28 "2018-11-30T19:02:44Z")
What State Plane Zone? I just loaded up our NAD 83 Colorado Central and the 0,0 point is roughly 50 miles North East of Twenty Nine Palms in California. Or maybe I don’t understand your question. [Previous page](https://boards.straightdope.com/t/map-location-question-zero-point-for-nad-83/825113.md?page=1)