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"the center of the Earth is off by about two meters"
December 11, 2013 8:24 PM   Subscribe

What Happens To Google Maps When Tectonic Plates Move?

GPS - Measuring Plate Motion (PDF)

David Potere, sensors, JUL 2008: Horizontal Positional Accuracy Of Google Earth's High Resolution Imagery Archive
These findings indicate that Google Earth high resolution imagery has a horizontal positional accuracy that is sufficient for assessing moderate-resolution remote sensing products across most of the world’s peri-urban areas.
Dr. Nagi Zomrawi Mohammed, Ahmed Ghazi and Hussam Eldin Mustafa, International Journal Of Multidisciplinary Sciences and Engineering, vol4 issue6 JUL 2013: Positional Accuracy Testing Of Google Earth (PDF)
Taro Ubukawa, Center for International Earth Science Information Network (CIESIN), MAR 2013: An Evaluation of the Horizontal Positional Accuracy of Google and Bing Satellite Imagery and Three Roads Data Sets Based on High Resolution Satellite Imagery (PDF)
Kazimierz BECEK and KHAIRUNNISA Ibrahim, Universiti Brunei Darussalam, MAY 2011: On The Positional Accuracy Of GoogleEarth Imagery(PDF)
In this project, the coordinates of the beginnings and ends of the centralines of runways well-visible in GoogleEarth® were compared with the coordinates of the corresponding runways extracted from the Global Elevation Data Testing Facility (GEDTF). The results demonstrate that there are inconsistencies in the position data provided by GoogleEarth®, and therefore caution must be exercised when using this service for certain purposes, such as navigation.
Postcards From Google Earth, previously
posted by the man of twists and turns (19 comments total) 22 users marked this as a favorite

 
Ronni Grapenthin's videos and data from the 2011 Tohoku earthquake
posted by the man of twists and turns at 8:26 PM on December 11, 2013 [1 favorite]


Can't they use feedback from people's GPS devices to calibrate the maps? If you log and upload GPS position data from vehicle navigation devices and visualize it you ought to see the data tracing out the outlines of major roads pretty clearly. There will be a bit of error from people not driving exactly in the middle of the lanes but it all ought to even out. Align these with the roads on your maps and you're done.
posted by L.P. Hatecraft at 8:38 PM on December 11, 2013 [1 favorite]


Can't they use feedback from people's GPS devices to calibrate the maps?

In related news, Ingress is out of invite-only I believe.
posted by carsonb at 8:46 PM on December 11, 2013 [3 favorites]


Turns out the Universe is made of rubber.
posted by localroger at 8:51 PM on December 11, 2013


Goggle Maps is off for my street address by over 100 yards (but so also are all the GPS systems) because the street numbers were somewhat haphazardly assigned in this semi-rural area over 80 years ago. The USPS mail carriers know where my mailbox and my front door are, and UPS and FedEx find me every time, but when Amazon.com uses one of their lesser delivery services, they get confused. I'm looking forward to having the Amazon Drone Quadcopter drop my order in an empty field south of here.
posted by oneswellfoop at 9:16 PM on December 11, 2013 [4 favorites]


“One of the many things we no longer have money to do is send out people to make sure those marks are still there,” Smith says.

Surely this is a hallmark of a civilization in decline? Things we once did we no longer do because of money...despite there being more more than ever in the world, as a whole.
posted by maxwelton at 9:30 PM on December 11, 2013 [7 favorites]


Things we once did we no longer do because of money

You got to the part where the shady over-funded military organization does the same thing but on a global scale, right? And you read the part about geocaching? (And now Ingress is a great route into the nerdy subculture.) I guess you can lament that the duties have fallen to those operating in secret and/or people doing it of their own accord, but it's not like the work isn't getting done at all.
posted by carsonb at 10:12 PM on December 11, 2013


This article neglects to mention the International Celestial Reference Frame. That's the reference for GPS.
posted by Nelson at 10:40 PM on December 11, 2013 [3 favorites]


We once used to measure the "constants", and every year the CRC Physics handbook would have new numbers... but those error bars and variability drove the powers that be a bit nuts... so they redefined almost everything in such a way that nothing can vary.... even if it does.

I suspect in the next few decades we'll all learn that the "constants" really aren't, and we should have kept paying attention to the details, instead of papering over them.
posted by MikeWarot at 10:54 PM on December 11, 2013 [1 favorite]


From the article: “Surveyors do not like it if coordinates change, so this is kind of a compromise.”

Many years ago when surveyors were first considering adopting GPS enabled equipment, I had a summer job looking up courthouse records for a surveyor. This issue doesn't just affect surveyors, there are thousands of pounds of paper-only records of surveys, tax maps, and plats in every courthouse in every city and county and state in this country. These records are not easily amended, I can't image there's not much incentive to digitize them.

In one summer on the job, I regularly ran into records that referenced surveys from the 17th and 18th century. Every person who owns land is depending on a system that where the coordinates are fixed and 200 year old railroad spikes are the gold-standard. Changing the coordinates is a lot more than an inconvenience to surveyors.

TL;DR, you should always invest in title insurance when you buy property.
posted by peeedro at 11:15 PM on December 11, 2013 [6 favorites]


Surely this is a hallmark of a civilization in decline? Things we once did we no longer do because of money...despite there being more more than ever in the world, as a whole.

The USAF Space Fence (that has been running since 1961) was turned off recently too. It did things ranging from tracking space debris, correcting satellite trajectories, helping to prevent satellite collisions and (presumably) mapping out the spy satellites of other nations.

And yet Western per capita GDP's continue to grow (and tax levels relative to GDP's haven't changed that much).
posted by ianbanks at 12:02 AM on December 12, 2013


This reminds me of the story about the high quality 3d model of all of London's geo data.
The plan was that it would be kept fully updated and be freely accessible.
So any time changes were made it would be updated and it would make life much easier for surveying and planning and so on.

It was cancelled because after six years of work Ordnance Survey wouldn't allow their data to be released.
posted by Just this guy, y'know at 2:06 AM on December 12, 2013


Also, this video (which is in the original linked article) shows real time GPS monitoring of the Japan earthquake. It's really rather astonishing.
posted by Just this guy, y'know at 2:13 AM on December 12, 2013


You got to the part where the shady over-funded military organization does the same thing but on a global scale, right? And you read the part about geocaching? (And now Ingress is a great route into the nerdy subculture.) I guess you can lament that the duties have fallen to those operating in secret and/or people doing it of their own accord, but it's not like the work isn't getting done at all.

The military's efforts notwithstanding (and since they're generally not the data-sharing types, the usefulness of their work to many purposes is limited) saying that it's okay because geocachers are now doing it is like saying we used to have a functioning public transport system, but never mind that they shut down all the buses and trains, we have rideshareonline.com now!
posted by Dysk at 4:37 AM on December 12, 2013 [1 favorite]


The difficulty with relying on any aggregated imagery is that you have very little idea of the metadata of the source images. Round here, Google and Bing use different suppliers for different zoom levels, so the offsets and skew vary. Right now, Bing seems to be updating the imagery of many small towns in Ontario, so instead of usable detail, there's a gaping hole in many municipalities.
posted by scruss at 6:29 AM on December 12, 2013 [1 favorite]


It's not impossible, I used to bulls-eye womp rats in my T-16 back home - they're not much bigger than two meters.
posted by petebest at 6:43 AM on December 12, 2013 [1 favorite]


But then it struck me: if nothing has fixed coordinates, then how do Google Maps, car nav systems, and all the other mapping services get you where you’re going? Presumably they must keep updating the coordinates of places, but how?

I figured I’d Google the answer quickly and get back to Einstein, yet a search turned up remarkably little on the subject. So, as happens distressingly often in my life, what I thought would take 30 seconds ended up consuming a couple of days.
I had basically this exact same experience a few weeks ago, and found that geodesy is the must mundane-sounding but incredibly complex wikipedia-rabbit-hole ever.
posted by kiltedtaco at 8:48 AM on December 12, 2013 [2 favorites]


Amen, kiltedtaco. One of the resume bullets I'm proudest of, but never say-so in interviews, is a packet of software tools I wrote to convert between the various spatial systems used on a project in Egypt.

"10 kilometers downrange" is a surprisingly complicated idea, once you worry about what it precisely means.
posted by IAmBroom at 10:35 AM on December 12, 2013


In related news, Ingress is out of invite-only I believe.

Heck, it's even leaving Beta Test status as of tomorrow.

(I'm hoping that this means they've got a workable solution to the GPS spoofer problem, as that would be an obvious milestone for a game of its type. The fact that the in game events of the last month or so have all the appearances of a honeypot to fine tune and acid test anti-spoofing algorithms while getting the userbase highly motivated to report accurately whether other players are or aren't at a specific location only serves to strengthen that hope).
posted by radwolf76 at 2:30 PM on December 13, 2013


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