Q: Did the Earth Move Darling? - Page 1
Forum section: electronics / general

author: German_EE
author_rank: Super Contributor
timestamp: July 29, 2016, 12:29:18 pm
content: A: Only if you are in Australiahttp://www.bbc.com/news/technology-36912700Looks like you are currently 1.5m out in your calculations which doesn't sound like a lot until you consider things like self driving vehicles.

author: Rerouter
author_rank: Super Contributor
timestamp: July 29, 2016, 12:36:06 pm
content: using a gps / glonass / bidou GPS receiver your approximate accuracy is only in the ball park of 0.7m, put a tree overhead, drive next to a multi story office block, etc and that may blow out to 1.3m,go anywhere near a city center and you will be lucky to find yourself on the correct block,The self driving cars argument falls a bit flat here, I used to deal with inertial navigation GPS units for cars, the hardware is on the $300 dollar mark for a functioning product that would cross compare your road speed / forward reverse, and where you turned corners to sync with its mapping data, so it still functioned in say a tunnel, or a very built up area,If a car with fancy enough vision systems to monitor lanes and such cannot afford to tack on such things and soley depended on GPS, then we are all doomed.

author: Tom45
author_rank: Frequent Contributor
timestamp: July 29, 2016, 02:26:42 pm
content: Australia is moving 7cm north per year? That seems like a lot. Are there any other places on the planet that move at that rate or faster?Does Australia have a problem with earthquakes? I don't remember hearing about any.Are the Kiwis tagging along or is New Zealand being left behind?

author: German_EE
author_rank: Super Contributor
timestamp: July 29, 2016, 02:52:51 pm
content: I know that India is moving north at a rapid rate as well, the result is the Himalayas and the Tibetan Plateau.

author: JacobPilsen
author_rank: Regular Contributor
timestamp: July 29, 2016, 08:32:56 pm
content: Quote from: German_EE on July 29, 2016, 02:52:51 pmWest China

author: VK5RC
author_rank: Unknown
timestamp: July 30, 2016, 01:42:14 am
content: One interesting fact that in my state, south Australia, the earliest satellite based maps were less accurate (due to errors in estimating the 'non-spherical' shape of the earth) than the maps produced by Matthew Flinders (a rather OCD character) a few centuries before! One boat actually ran aground a rocky outcrop at night due to this 'error'

author: hendorog
author_rank: Super Contributor
timestamp: July 30, 2016, 03:07:18 am
content: Quote from: Tom45 on July 29, 2016, 02:26:42 pmIts OK they can go, we are quite happy where we are.Maybe soon their snoring won't keep us awake.

author: SkyMaster
author_rank: Frequent Contributor
timestamp: July 30, 2016, 03:18:54 am
content: Quote from: Tom45 on July 29, 2016, 02:26:42 pmNot a "place" per se, but...The Magnetic North Pole is moving at a rate of 60 km per year.In the '70s, it was moving at "only" 9 km per year; so something is going on. Poles reversal maybe.

author: tautech
author_rank: Super Contributor
timestamp: July 30, 2016, 03:48:02 am
content: Quote from: hendorog on July 30, 2016, 03:07:18 am+1Let the Aussies go walkabout.

author: Halcyon
author_rank: Unknown
timestamp: July 30, 2016, 06:46:20 am
content: Quote from: Tom45 on July 29, 2016, 02:26:42 pmGenerally not. Minor tremors are common but most aren't even felt. Those that cause damage are fairly rare. This is one of the reasons Australia would be an excellent place for nuclear power. But that's another argument ;-)If you're interested, you can view earthquake data here:http://www.ga.gov.au/earthquakes/

author: Arjan Emm
author_rank: Regular Contributor
timestamp: July 30, 2016, 08:14:24 am
content: Australia sits quite comfortable in the middle of the very stable australian plate. Hence very little earth quakes.The whole plate is moving north and on the edges where it collides with other plates is where you get the earth quakes.It collides in the north to the eurasian plate en several others. Right on the edge you find the geological mess called indonesia, papua new guinea, solomo islands and vanatu. Highly volcanic and losts of very large earthquakes.In the south east, New sealand sits partly on the australian plate (North island) and partly on the pacific plate. The pacific plate pushes the south island against and up the australian plate hence the mountains there. So i'm afraid the kiwi's are keeping up with australia just fine. But with a bit more geological discomfort...

author: nctnico
author_rank: Super Contributor
timestamp: July 30, 2016, 08:17:36 am
content: Quote from: Rerouter on July 29, 2016, 12:36:06 pmMake that +/80 meters! A long time ago I was responsible for a car which was used for recording how people drive. It had a GPS receiver to determine the location of the car. I used the GPS locations in my software to cut the interesting bits from the data (intersections, roundabouts, pieces of straight road, -whatever the researcher needed-). It quickly became obvious that the GPS wasn't accurate at all and I have to do some filtering / interpolation on it to get more accuracy. BTW most roads have lanes which are close to 4 meter in width so 1.5 meter is not going to make a difference. People think GPS is always accurate but it isn't. Not by a long shot! What you see in navigation systems is that it guesses on which road it is by using the GPS for a rough location and direction,

author: Iron Downey
author_rank: Contributor
timestamp: July 30, 2016, 08:29:18 am
content: The earth is absolutely moving. According to the theory of plate tectonics, the earth is moving all the time. You can also see this by the growing of Everest (Qomolangma)

author: hendorog
author_rank: Super Contributor
timestamp: July 30, 2016, 08:37:07 am
content: Quote from: tautech on July 30, 2016, 03:48:02 amIf we ignore them they will go away

author: Muttley Snickers
author_rank: Unknown
timestamp: July 30, 2016, 09:36:22 am
content: If this concept of continental drift or similar was found to be true then my only concern would be the possibly of gradual migration of animal and insect species, those people in Sydney could end up with cane toads from Queensland and us lot in Melbourne could find ourselves being dragged into big holes made by funnel web spiders, in which case I will be off to Tasmania.

author: Halcyon
author_rank: Unknown
timestamp: July 30, 2016, 09:53:05 am
content: Quote from: Muttley Snickers on July 30, 2016, 09:36:22 amDon't joke! Tasmania is absolutely beautiful. If I wasn't already paying a mortgage, I'd buy there in a second.

author: Arjan Emm
author_rank: Regular Contributor
timestamp: July 30, 2016, 10:10:01 am
content: Quote from: Muttley Snickers on July 30, 2016, 09:36:22 amYou got to be kidding me, do you have doubts about this? Any geologist knows this is a fact and has been proven over and over.Intercontinental drift doesn't happen so don't worrie about sydney moving to melbourne.A continent, the australian plate in this case might split up though and drift appart. This is happening in africa but no signs for this on the australian plate.

author: timb
author_rank: Super Contributor
timestamp: July 30, 2016, 10:44:06 am
content: Quote from: nctnico on July 30, 2016, 08:17:36 amHow long ago is "a long time"? If it was before 2000, the additional error was due to Selective Availability, which was switched on up to that point by the US Armed Forces (it intentionally crippled civilian GPS to prevent our enemies from building cruise missiles out of off the shelf GPS receivers, or some such BS).Though, even with SA on, you could have used Differential GPS to eliminate the SA imposed accuracy penalty. If you weren't in an (primarily coastal) area covered by a DGPS transmitter, there were also commercial DGPS services that worked all over North America. One was satellite based and another used local FM radio stations to rebroadcast the signal. (These would have been available since at least 1996 and was part of the reason SA was finally turned off.)The advent of WAAS (which is DGPS data being retransmitted by one of the GPS satellites), high channel count receivers, SA being turned off and dramatic improvements in signal processing technologies is the reason why we can get sub-1m navigation out of receivers that are smaller than a penny with rice grain sized antennas.I remember a time when the Garmin GPS 45 was *cutting edge* with its huge swivel out antenna and 6 hour battery life...

author: GreyWoolfe
author_rank: Unknown
timestamp: July 30, 2016, 12:13:25 pm
content: Quote from: nctnico on July 30, 2016, 08:17:36 amThe home location on my Garmin Nuvi 1490 is 4 houses away despite setting home location while in the driveway

author: Nerull
author_rank: Frequent Contributor
timestamp: July 30, 2016, 02:59:06 pm
content: There's a reason aircraft don't use GPS for autopilot landings, and there's a reason self-driving cars don't use GPS for lane positioning. It's simply not accurate enough, especially not 24/7.

author: boffin
author_rank: Unknown
timestamp: July 30, 2016, 05:48:37 pm
content: The US is moving at a rapid rate too. Toward the dark ages.

author: SkyMaster
author_rank: Frequent Contributor
timestamp: July 30, 2016, 06:47:59 pm
content: Quote from: timb on July 30, 2016, 10:44:06 amActually, the WAAS signals are being transmitted by three dedicated geostationary satellites that arenotpart of the GPS satellite constellation.

author: German_EE
author_rank: Super Contributor
timestamp: July 30, 2016, 06:48:50 pm
content: "The home location on my Garmin Nuvi 1490 is 4 houses away despite setting home location while in the driveway"I have a similar problem with a TomTom Start GPS unit, the error is about 200m. There is a similar problem with road junctions, when I'm at the junction it still says I have 200m to go.

author: timb
author_rank: Super Contributor
timestamp: July 30, 2016, 10:11:48 pm
content: Quote from: Nerull on July 30, 2016, 02:59:06 pmActually, the whole reason WAAS/SBAS was developed (by the FAA) was to provide an alternative to ILS for Category I precision approaches to airports. It provides 0.9m lateral and 1m vertical precision, which will put you on a near perfect final approach. All the pilots have to do is touchdown.There's also a new system dubbed LAAS/GBAS (Local Area Augmentation System or Ground Based Augmentation System) to enable autoland (Category IIIC) at any airport with the system installed. Basically you place at least three GPS receivers around the airport, which talk to a central server, that applies correction data and transmits it to the plane on a VHF link.The cost to setup a GBAS system is many times less than what a traditional ILS system would cost, and it's more accurate!As for self driving cars, ~1m accuracy is good enough, especially when combined with highly accurate maps, correction algorithms and a slew of sensors.Quote from: SkyMaster on July 30, 2016, 06:47:59 pmWell, yes, technically they are three separate satellites that are not part of the GPS constellation, but they *are* part of the GPS system. Plus, they also broadcast standard GPS signals, in addition to the WAAS data, so they're generally considered to be GPS satellites.

author: SkyMaster
author_rank: Frequent Contributor
timestamp: July 31, 2016, 12:54:24 am
content: Quote from: timb on July 30, 2016, 10:11:48 pmClose, but no cigarThe WAAS satellites do not broadcast any GPS signal.The GPS satellites are owned by the United States government. But it is not the case for the WAAS satellites.The three satellite that are being used to transmit the WAAS signals are all privately owned satellites. The are common geostationary telecommunication satellites that also serve other purposes; one of these satellite is owned by a Canadian company.GPS is managed by the Department of Defense (DOD)WAAS is managed by the Federal Aviation Administration (FAA)WAASis notGPS. WAAS allows theGPS receiverto improve the GPS signal accuracy; at the receiver level.The GPS system is unaware of the WAAS existence

author: timb
author_rank: Super Contributor
timestamp: July 31, 2016, 01:10:41 pm
content: Quote from: SkyMaster on July 31, 2016, 12:54:24 amThe US Air Force (who oversees the development an management of both the space and ground control segments of GPS) and the FAA are both part of the United States Federal Government. And while they might not own the WAAS satellites out right, at the very least they lease space on them. I'm not even sure lease is the right word, as the satellite transponders to re-broadcast the signal would have been designed and implemented specifically for WAAS by Raytheon and the satellite operators under contract.Sure the associated satellites are multipurpose, but that doesn't mean they can't provide other GPS functions in addition to providing the DGPS correction data. (Like providing almanac or epherimis data.)Here's what the Wikipedia article on WAAS says:"The space segment consists of multiple communication satellites which broadcast the correction messages generated by the WAAS Master Stations for reception by the user segment.The satellites also broadcast the same type of range information as normal GPS satellites, effectively increasing the number of satellites available for a position fix.The space segment consists of three commercial satellites: Inmarsat-4 F3, Telesat's Anik F1R, and Intelsat's Galaxy 15."Though, that is Wikipedia so take it with a grain of salt I suppose. Also, after thinking about it, I wouldn't imagine a commercial communications satellite being equipped with the required atomic clock and other hardware needed for GPS.

author: SkyMaster
author_rank: Frequent Contributor
timestamp: July 31, 2016, 03:06:22 pm
content: Quote from: timb on July 31, 2016, 01:10:41 pmIt is true that Wikipedia is not reliable. Wikipedia is not a source of knowledge. At best, Wikipedia is a source of "information". Often, Wikipedia is a source of misinformation; anybody can write anything in Wikipedia.WAAS is not GPS. The satellites used for WAAS are not part of GPS.We can put that one to bedThere are several official documents, that can be found on-line, that describe GPS, and WAAS, in great details.Below are two links that popularize the Wide Area Augmentation System (WAAS).The first is from an avionic shop, the second is from the Federal Aviation Administration:How WAAS Workshttp://www.avionicswest.com/Articles/How%20WAAS%20Works.htmlSatellite Navigation - WAAS - How It Workshttp://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/waas/howitworks

author: jc101
author_rank: Frequent Contributor
timestamp: July 31, 2016, 03:47:57 pm
content: Q:Did the Earth Mode Darling?A: No, but the wardrobe door came open.** to quote the late Victoria Wood.Although her ballad to Barry and Freda gave it a try..

author: Nerull
author_rank: Frequent Contributor
timestamp: July 31, 2016, 05:09:10 pm
content: Quote from: timb on July 30, 2016, 10:11:48 pmCat I approach is not the same thing as autoland, and unaugmented GPS or WAAS will never be good enough for that.Yes, if you have local GPS corrections being transmitted to the receiver it can be quite accurate, but that accuracy is confined to locations with such transmitters. And even then, its not actually approved for use yet.And none of that really solves the problem of basing our entire mapping system on a fixed unchanging coordinate system when continents are moving.

author: timb
author_rank: Super Contributor
timestamp: August 01, 2016, 12:06:59 am
content: Quote from: SkyMaster on July 31, 2016, 03:06:22 pmI understand how WAAS works and understand it's not GPS. I never said it was. (WAAS is essentially DGPS, only using satellites to transmit the data to receivers, versus VHF or FM radio.)However, if they wanted to, there's no reason they couldn't put a WAAS transponder on a GPS satellite. (In fact, there was talk about doing just that with some of the new IIIa block GPS satellites that will be put into service in the coming years; not sure if they decided to do it or not.)You might want to read the FAA link you posted:"The navigation payloads broadcast the augmentation messages on a GPS-like signal. The GPS/WAAS receiver processes the WAAS augmentation message as part of estimating position. The GPS-like signal from the navigation transponder can also be used by the receiver as an additional source for calculation of the user’s position."This is what I've been trying to say: WAAS satellites also provide GPS-like data to aid in position fix, in addition to the correction data. So the quote from Wikipedia is in fact correct. I wonder if a non-WAAS receiver can see (or lock) to one of the WAAS satellites. Hmm, I might test that.Edit: I just went back and looked; originally I said WAAS was broadcast by the GPS satellites, which is what you corrected me on. You're technically right in that they're not GPS satellites. For some reason, I thought I said WAAS messages were broadcast as part of the GPS *system* which *is* true and what I was initially arguing about.