In a project, we need the exact location of the products (with an accuracy of finally two centimeters)
Can anyone make a circuit to make a GPS with this precision?
Last Edited: Fri. Jul 31, 2020 - 09:32 PM
High accuracy position device (like GPS)
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Use a laser sensor...you can measure exact distance to any point. Have you even looked at GPS? What does it mean to know where you are in Atlanta to 2cm? Based on what? At most you can have a nearby referencepoint with a transmitter ast the reference.
You need to supply a LOT more details concerning you needs, provide a FULL and complete description
Last Edited: Fri. Jul 31, 2020 - 06:19 PM
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hasanzadeh99 wrote:
we need the exact location of the products (with an accuracy of finally two centimeters)
Over what range?
Indoors or outdoors?
Are the "products" stationary?
Are there any constraints you could take advantage of; eg, products will be on shelves or in bins ... ?
Have you looked at the location features in the latest revision of Bluetooth 5 ?
hasanzadeh99 wrote:
Can anyone make a circuit to make a GPS with this precision?
google "differential GPS" aka "DGPS"
also google "Real Time Location/Locating System" or "RTLS"
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We use DGPS to measure the position of cars accurate to cm to be used as a groundtruth, so quite feasible.
Rtk gps does 2cm. Just be prepared to pay for it. I was using this stuff 10 years ago. Using GNSS should be a little cheaper now.
In a building or in open space?
Jim
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avrcandies wrote:
You need to supply a LOT more details concerning you needs
Indeed - as the subsequent posts have shown!
https://www.decawave.com/ is another one to look at
Note that Decawave were recently acquired by Qorvo - so that link may not last ...
https://www.qorvo.com/newsroom/news/2020/qorvo-completes-acquisition-of-decawave
Hey all
In open outdoor.
We want to specify some points in a road and save accurate position of them .
Transit and a surveyor's tape measure. Add a bit of trigonometry, and you are "there".
Jim
Virtually all surveying is done with GNSS. So i think that is your answer.
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hasanzadeh99 wrote:
Hey all
In open outdoor.
We want to specify some points in a road and save accurate position of them .
and you need to have 2cm precision for that???????
Sounds more like a thing for defense were they want to hit a target with superb precision........
Perhaps have a look at road working equipment, they used to use DGPS and as such know with relative precision were they are compared to a known point nearby.
all of GPS technical instrument has above 1meter accuracy.
We want to set some device under ground but set their location before repair their place.
tnx
I wish you all the luck in the world.
Rubbish! Survey grade GPS/GNSS has done 2cm accuracy for many years. It might be difficult to obtain in your part of the world though. There’s a ship off the coast of Dubai that has a system I designed many years ago.
hasanzadeh99 wrote:
all of GPS technical instrument has above 1meter accuracy.
We want to set some device under ground but set their location before repair their place.
tnx
You want to bury something in the ground, and be able to find it again at some time in the future ?
https://en.wikipedia.org/wiki/Sa...
The translation doesn't look as comprehensive: https://fa.wikipedia.org/wiki/سامانه_ماهواره%E2%80%8Cای_ناوبری_جهانی
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hasanzadeh99 wrote:
all of GPS technical instrument has above 1meter accuracy.
Please read the replies carefully: everyone is suggesting Differential GPS - DGPS.
DGPS certainly does give the accuracy you require.
hasanzadeh99 wrote:
We want to set some device under ground but set their location before repair their place
It's still not clear what you mean by that!
- You want to record its location before you bury it?
- It is already buried, and you know its location to within 2cm?
- It is already buried, but you don't (accurately) know its location - so you need to find it?
- Or what??
Even normal GPS positioning error is of a Gaussian distribution, so one could simple put a data logger on site and record 1000 or 10,000 readings and average them on a PC for a really good reading.
JC
Even normal GPS positioning error is of a Gaussian distribution, so one could simple put a data logger on site and record 1000 or 10,000 readings and average them on a PC for a really good reading.
hmm... I bet there could be some bias error (not sure)...at least it would reduce the variance. I started proposing using GPS for positioning equipment in 1988...was flatly told...no, this is for military use only! Then 4-5 years later we, were all over GPS, with some very early systems (as a user, not GPS maker). We hired some guys to cost reduce the GPS board set with some clever "tricks", but in the year or two of their proposal, the board prices fell so much all their work was thrown in the trashcan.
My brother did some long term tests with his commercial Garmin GPS. Over a period of days, the reported location wandered around several meters. It did not appear to correlate with time of day or with weather. This would indicate that simple "averaging" would have to run over a really long time.
DGPS, on the other hand, as I understand it, compares the current GPS readings between two receivers that are not terribly far apart (hundreds of meters, max). It assumes that propagation and similar errors will be the same for both, so by looking at the difference, you can get a higher precision distance between the two (rather than absolute physical location). DGPS is used for precision aircraft landing systems (much lower minimums than standard IFR approaches). It is also used for surveying and other applications where distance is the important metric, instead of absolute physical location. By the way, DGPS uses an RF link between the base unit and the remote (usually mobile) unit so that the mobile unit knows the base data in real time.
Jim
DGPS, on the other hand, as I understand it, compares the current GPS readings between two receivers that are not terribly far apart (hundreds of meters, max).
We were doing diff GPS in the mid 90's & spending big $$$$$, one of the low cost options was to get a radio subscription service...some FM stations were using their data subcarriers (similar to paid MUZAK channels) to send data that had a stream of local deviations. So instead of needing a secondary local box, you could download the "current" deviation for your general locale and get a much "better" fix... My guess is that went by the wayside as costs fell & things got better....or maybe it is still used. In a rather strange twist, our president at Spectra-Physics left to become the president of Trimble; then a year later Trimble bought our local division of Spectra-Physics.
https://www.ion.org/publications/abstract.cfm?articleID=4323
Last Edited: Mon. Aug 3, 2020 - 06:50 PM
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Jeez, GPS is for the earthly location of an object as determined from outer space. And two centimeter resolution from outer space means only one thing: top secret military.
Are you trying to put a bullet into the top-dead-center of someone's head from outer space and are worried that you might just nick their ear instead???
That's what it sounds like you are trying to do.
Please, be serious. If you need to determine whether or not an obstacle is located within a range of two centimeters, then you are talking about using a proximity sensor IC, not GPS!
I can see wanting to determine if a road surface deforms or flows over time. No "jeez" needed for that. Or military, either. Prox sensor no help, either.
JIm
We never imagined how low cost GPS would get to be...since we were into laser scanner systems, we developed some positioners based on that, using long range bar-codes (few hundred feet).
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Simonetta wrote:
two centimeter resolution from outer space means only one thing: top secret military.
Nonsense.
2cm accuracy is easily achievable with commercial equipment; eg,
OS, the British mapping agency, wrote:
How accurate is GNSS?
Using a single receiver, without any additional corrections, a civilian user can achieve a positional accuracy equal to 5–10m 95% of the time, and a height accuracy of 15–20m 95% of the time.
Combined with data or corrections from a service such as OS Net, a positional accuracy of 1–2cm is achievable. (Depending on hardware and environmental factors.)
https://www.ordnancesurvey.co.uk/business-government/tools-support/os-net/positioning
Wikipedia wrote:
A Differential Global Positioning System (DGPS) is an enhancement to the Global Positioning System (GPS) which provides improved location accuracy, in the range of operations of each system, from the 15-meter nominal GPS accuracy to about 1–3 cm[1] in case of the best implementations.
Simonetta wrote:
Please, be serious.
EDIT
add Wikipedia quote
EDIT 2
And RTK GPS has also been mentioned:
Wikipedia wrote:
Real-time kinematic (RTK) positioning is a satellite navigation technique used to enhance the precision of position data derived from satellite-based positioning systems (global navigation satellite systems, GNSS) such as GPS, GLONASS, Galileo, NavIC and BeiDou. It uses measurements of the phase of the signal's carrier wave in addition to the information content of the signal and relies on a single reference station or interpolated virtual station to provide real-time corrections, providing up to centimetre-level accuracy.[1]
and they even state some clearly non-military applications:
It has applications in land survey, hydrographic survey, and in unmanned aerial vehicle navigation.
Last Edited: Mon. Aug 3, 2020 - 10:15 PM
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Kartman wrote:
Some are zero price for the service with a cost that's dependent on distance from the transmitter (latency, receiver price and cost)
Just be prepared to pay for it.
Cost – RTK2GO via Where Do I Get RTCM Corrections? | What is GPS RTK? - learn.sparkfun.com
via SparkFun GPS-RTK Dead Reckoning pHAT for Raspberry Pi - GPS-16475 - SparkFun Electronics
due to a new arrival
GPS-RTK Dead Reckoning pHAT for Raspberry Pi - SparkFun | Mouser
I think DGPS is usually considered accurate to about 10 cm, while the somewhat different WAAS GPS can easily be accurate to 2 cm, or better.
JC
https://www.instructables.com/id...
Worth noting that GPS is not the only one in town. There's Galileo, Beidou, Glonass and a couple more satellite constellations. Like Coke, GPS has become the generic term for satellite positioning. The more general term in GNSS.
Positioning accuracy depends on the number of 'observations'. Each satellite gives you an observation. Many receivers these days will track 20+ satellites concurrently thus giving good accuracy. This is enhanced by corrections which are obtained by fixed base stations at known and static locations. Your mobile phone can give better than 1m accuracy in the right conditions as the cell system is timed by GPS and outputs corrections. There are also other services that you can obtain a correction stream from.
One of the big breakthroughs with commercial GPS accuracy was the ability to extract information from the military L2 frequency. Whilst this is encrypted, the phase information is used to obtain more observations. Being a slightly different frequency, it gets affected differently in the path from the satellite to the receiver. These differences can be used to infer different paths and atmospheric affects. The other breakthrough is the cell system - getting correction data is easy. With my early systems, we have base stations to generate our corrections.
What I find interesting about GPS/GNSS is that it is not a absolute measurement. It is a bit like a murder mystery where the detective interrogates a number of people and filters out the facts from the noise to arrive at a conclusion. With GPS/GNSS you don't get a confession though. What you do get is an estimation with an error probability. Depending on your equipment and the environment, better than 2cm CEP ( circular error probability) is easily achievable with commercially available systems. It is still quite expensive for this accuracy, but the price is dropping. With the commercial equipment there are limitations of alititude and velocity so you can't use them in rockets or missiles. You have to ask nicely to bypass these limits.
Farmer use tractors with high accuracy GPS/GNSS to plow their fields, road builders use it with their heavy machinery to guide the excavators etc. It's been around for quite a few years.
How did we do this before GPS, e.g. for subterranean public utilities like water pipes and phone cables ? A written register of device locations to get you close (e.g. street address, bearing from some PoI), then an above-ground marker for precise location. I can several from my window as I type.
Easier in a developed urban setting, less so in the middle of a desert.
Unless of course it's hush-hush and you don't want to advertise its presence.
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very often, there is no (accurate/reliable/complete) record of underground utilities - so it's a matter of trying to detect them by some means, and then digging carefully.
This very thing has caused some significant delays to major infrastructure projects around here in recent years
That may be so, but that's neither an excuse nor an inevitable outcome for a properly-designed and managed system. An automated system might offer efficiency and accuracy, but humans can still screw it up. The Ordnance Survey survived for a couple of centuries using paper.
Am I right in thinking that anyone, anywhere can consume GPS et al signals with the appropriate receiver, but DGPS requires additional, local terrestrial infrastructure ?
but DGPS requires additional, local terrestrial infrastructure ?
As mentioned, some of that info was beamed over radio stations for a subscription price...maybe a few still are (not so sure). In lieu of that, the correction info needs to come from somewhere & of course needs to be an accurately surveyed (known) nearby location. Its basically saying, all reading in this vicinity are off by some parameters xxxx ....so you can apply that to your nearby readings.
avrcandies wrote:
but DGPS requires additional, local terrestrial infrastructure ?
As mentioned, some of that info was beamed over radio stations for a subscription price...maybe a few still are (not so sure). In lieu of that, the correction info needs to come from somewhere & of course needs to be an accurately surveyed (known) nearby location. Its basically saying, all reading in this vicinity are off by some parameters xxxx ....so you can apply that to your nearby readings.
Which is fine if you live in the 'developed world' (europe, n america, se asia) but a non-starter elsewhere. I think the OP is 'elsewhere'.
OP hasn't said much at all.
Where he is located within the world, or where in the world his project needs to work.
Number of items for which the needs the precise location.
Area over which the object ( s ) travel, several meters, or across the ocean in a shipping container?
Velocity and altitude at which the object ( s ) move.
Power source available to the tracking device.
How the tracking device will report its data, (real time, after-the-fact, NF/ BT, WiFi, Sat Phone, …)
Budget for the project?
What the items to be tracked are, (aircraft landing at an airport, delivery trucks, bull dozer and road grader, surveyor, etc.)
What the location update rate is?
What is the current system in use, and why does one wish to "improve" upon it?
.
.
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JC
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There are inexpensive LoRa gateways.
Setting Up A Base Station | GPS-RTK Hookup Guide - learn.sparkfun.com
[next to last paragraph]
Heads up! We’ve been experimenting with various LoRa solutions and the bandwidth needed for RTCM (~500 bytes per second) is right at the usable byte limit for many LoRa setups. It’s possible but you may need to adjust your LoRa settings to reach the throughput necessary for RTK.
...
Low power M2M cellular is also mentioned at SparkFun Electronics.
Commercial DGPS surveying setups have a master and one or more slave receivers. Each slave is able to determine its distance from the master to a cm-scale precision. Whether or not this results in a precise lat/lon depends on the precision of the position of the master.
Aviation use has a permanently installed master,. typically at an airport, and any suitably equipped aircraft can use that master as an element for precision approaches.
Thus, the "infrastructure" depends on the application. For surveying, you supply both the master and one or more slaves. For aviation approach use, you simply supply an appropriate slave, using a permanent master.
Jim
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obdevel wrote:
Don't know about anything else but GPS is a fairly late addition to commercial aviation. Before that planes used an inertial navigation system which involved setting the aircraft's position to a known datum before flight (the exact coordinates of the gate it was parked at) then gyros in all 3 axis would subsequently determine movement in any axis relative to that datum to know where the aircraft was in 3D space at any time.
How did we do this before GPS,
https://en.wikipedia.org/wiki/Inertial_navigation_system
Pre GPS and post mechanical gyro were the ring laser gyros. I worked on a project for the Air Force to simulate these for navigation training.
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obdevel wrote:
How did we do this before GPS,
With manual / mechanical / optical instruments: https://en.wikipedia.org/wiki/Surveying#History
e.g. for subterranean public utilities
relied on survey & measurement data being manually recorded on hand-drawn plans
The Egyptians must've had some good techniques.
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and the Romans - but what have they ever done for us ... ?
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awneil wrote:
and the Romans - but what have they ever done for us ... ?
well they 'gave' you Hadrians wall.......
and a lot of stuff to dig up that is still covered up after all these years
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Well, this just popped up in my Twitter:
ESPrtk wrote:
ESPrtk
The best choice for wireless RTK positioning applications.
Compatible with the latest protocols and latest generation RTK receivers, provides comprehensive solutions ,multi-application .
What is ESPrtk ?
ESPrtk is a small circuit board used to transmit wireless GNSS data in high precision positioning applications. ESPrtk is geared towards the ability to use high quality, independent, wireless and low cost platforms. ESPrtk’s heart is a powerful ESP32 processor.
May be worth a look: https://esprtk.com/
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Microwaves & RF wrote:
Magnetic-Field Navigation as an “Alternative” GPS?
Using measurements of anomalies in the Earth’s magnetic field and machine learning to extract data from raw signals, then matching them to accurate magnetic-anomaly maps, it may possible to navigate aircraft with reasonable accuracy independent of GPS.
Does that include the Bermuda Triangle too? 
Who wants to go first?
Jim
Great!
Now TSA will be checking all passengers about to board a flight for any Neodymium magnets that they might have in their pockets!
JC
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C099-F9P Application Board - u-blox | DigiKey
u-blox's C099-F9P application board features easy evaluation of the u-blox ZED-F9P with multi-band RTK
...
use cases
- absolute
- relative
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in RTK mode, 2cm CEP horizontal and 3cm vertical :
OpenRTK330LI EVK Developer Kit - ACEINNA | Mouser
ETA 1-Mar'21
OpenRTK Developer Manual — Aceinna OpenRTK Developer Manual documentation
Expect that is export-controlled!
Jim
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slightly
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