7:34 This is slightly wrong. *Special* Relativity says that the satellite clocks run SLOWER due to relative speed. However, *General* Relativity says that the satellite clocks run FASTER because they experience less of Earth's gravity. The gravity effect is far greater than the speed effect, and so the satellites have a net gain in clock speed.

@vishnu9264

2 жыл бұрын

blah blah blah blah just shut up

@carissamace

2 жыл бұрын

@@vishnu9264 They’re just giving legitimate criticism.

@johnlacey3857

2 жыл бұрын

It’s true - both special and general relativistic effects need to be taken into account. Failing to do so introduces range errors on the order of tens of meters(!) on the face of the earth - surprisingly significant for something most of us rarely think about in our daily lives.

@antipoti

2 жыл бұрын

Thank you! I was about to comment the same thing.

@49metal

Жыл бұрын

Not slightly wrong, gravely wrong. A mess.

The video provides a good simple illustrations and a good description of how GPS works. The narration of the video is really high quality. The accompanying article, "How Does Marine GPS Work?", mentioned in the video (link provided) provides a concise document that corresponds to what is covered in the video. Casual Navigation also provides another article, which is a great tutorial on navigation, "What is a nautical mile and why is it used?". Look for the link at the end of the article mentioned above. In my opinion, all three are well worth the investment in time.

This is the best explanation of gps technology.

@CasualNavigation

5 жыл бұрын

Thanks Bruno. Glad the explanation worked out

@KainyStyle

5 жыл бұрын

Was just going to write this, the other videos I watched felt like the "explainers" had no idea what they were talking about and were just reading Wikipedia page.

@ZackWolfMusic

5 жыл бұрын

No it's not. GPS does not run on satellites. It runs on high altitude balloons.

@KainyStyle

5 жыл бұрын

@@CasualNavigation Not both?

@SkyForceOne2

4 жыл бұрын

@@ZackWolfMusic dont forget your tinfoil hat, lmao

I stumbled on to your videos and found them extremely interesting. I subscribed to your channel and look forward to seeing all your videos. You do a great job at explaining things visually and verbally! Keep up the great job you're doing.

FYI: if you see a clock running FASTER than your own, that's not due to speed. Special relativity is symmetrical, as motion is relative, every observer thinks they are standing still. So every observer sees other objects' clocks running at the same speed (when stationary relative to them) or slower (when moving in some direction). The faster clocks come from being farther up from the gravity well, which is general relativity.

The best GPS video. Summarizes many topics under the GPS quite brilliantly.

@CasualNavigation

5 жыл бұрын

Thanks Maneeb

The relativistic time dilation is not only due to the speed (you've got that backwards), but also from the gravitational potential (it is farther away from the earth, with less influence from Earth's gravity). Search about *gravitational time dilation*. Literally, you head is literally getting older faster than your feet. The speed actually would make the clock to slow down (the faster you travel, the slower the time passes, compared to the rest), but the gravitational potential wins (the farther you are from the source of gravity, the faster it goes), so the net effect is that the time in the satellite goes faster than the Earth.

Not reall was looking for anything just got interested in one of your videos and now I’m stuck here listening to explanations of boats and signals The best part is that is casual and the edits are simple

I have searched every video on KZread for GPS but this one is best excellent explanation good voice and animation very easy to understand keep it up bro

Excellent video! I would include: With only 1 satellite the position will be within the surface of a sphere. With a second satellite, the position will be within the intersection of 2 spheres; that is, a circle. With the 3rd satellite the position will be within the intersection of the circle and the sphere; that is, 2 points. With the fourth satellite you will have a unique possible position. More satellites will increase accuracy.

Such a good explanation man. Thanks a lot. It was very helpful.👍

Best GPS video explained i'v seen on youtube. THANK YOU SIR, APPRECIATE IT.

Well explained and illustrated, thankyou.

@pritam9645

3 жыл бұрын

How does the satellite knows that the receiver has received the signal??

@pappafritto

3 жыл бұрын

@@pritam9645 it doesn’t it’s just an emitter

you doing very clear explanations ... keep up the good work ..

@CasualNavigation

5 жыл бұрын

Cheers ali

@pritam9645

3 жыл бұрын

@@CasualNavigation how does the satellite knows that the receiver has received the signal?

As a gps software engineer, this is very good. It may be beyond explaining how but r.t.k. gps receivers can achieve accuracies less than a quarter inch. Making them useful for survey applications..

@phizc

Жыл бұрын

I just read the Wikipedia page thanks to your comment. Cool stuff. Any idea how feasible it would be to have base stations on cell towers and have them act as CORS nodes? We'll need something like that for autonomous vehicles to become practical. LIDAR is well and good, but knowing the position of the vehicle relative to the road with 1-2 cm accuracy in snow and rain will be crucial.

@stevencolborne6845

Жыл бұрын

@@phizc the biggest problem is economics, rtk receiver are very expensive. But other than that weather will degrade performance. In other words difficult but not impossible.

very helpful , and the explanation was very clear.

Very clear and not too complicated. Great

You cleared my all doubts. Thank you

Congratulations on 10k subscribers! YT just recommended one of your videos and you had exactly 9999 subscibers so I thought might as well be your 10000th subscriber :)

@CasualNavigation

5 жыл бұрын

Thanks Mario. 10k is unbelievable to me already. Huge thanks to everyone who has enjoyed the content enough to subscribe.

@Mr._Doge

3 жыл бұрын

@@CasualNavigation 2 years later, 23 times more subscribers. You deserve it man!

Now I finally understand. Thank you!

Since you're a pilot, it would be interesting to know if you use any special GPS equipment. I watched a video on piloting in the Houston Ship Channel, and the pilot brought on his own high quality GPS system and attached it to the ship. Then it was related to the position on the ship and the specific dimensions of the ship, so they had a very accurate representation of the exact position of the ship in the channel. They've got really tight space restrictions in the most inshore end of the channel. It's also one of the relatively rare navigable non military places that no unauthorized boats or ships are allowed in the US. The combination of the narrow confines and the strategic significance of all those oil processing and loading facilities mean that there's a big sign, as well as protective measures to prevent any non-authorized vessels from going there. There is a free tour I'd like to take sometime.

Great explanation! Would be even better if you can provide the link to an article which describes the distance calculation part in a bit more detail! Would love to know the mathematics behind it.

@CasualNavigation

5 жыл бұрын

Thanks Abhishek. I'll see if I can do that for next time - add extra links for more in depth answers. Cheers for the feedback

you really do a good job tricking people into a physics class

Thanks. Again very good explanation on GPS.

Well explained what to do if sender and receiver have different times.

Really nice job. If you felt up to it, you could do a video on Space-Based Augmentation (SBAS) such as the WAAS system in the US or EGNOS in Europe. These are ways to augment GPS to improve performance and integrity using a network of fixed known ground-based receivers - basically an extended implementation of Differential GPS.

The relativistic error comes mainly from the theory of General Relativity, the sattelites are further out of the gravity well that is the earth and therefore their clocks run faster compared to our clocks on (or near) the surface.

@user-bf1zg6tx6u

4 жыл бұрын

both effects take place and must be accuunted for

@supawooky

3 жыл бұрын

actually TobyAsE120 is right, (the video explains it wrong, from our frame of reference a fast moving object should experience a slowing of time, but) since that speed is really not that great compared to the speed of light, the gravitational effect on time is much greater here and so it actually IS the main reason satelites' clocks run faster.

@foty8679

2 жыл бұрын

@@supawooky And technically the guy above you is right.

Very clear presentation, thanks

Great job!

It’s not triangulation, it trilateraration. Good video.

These video is really helpful sir thanks

when i studied linear algebra i got so mindblown by this

Sir please upload more videos on maritime equipment and operations. Which r used on ships at sea.. thank you 😊🚢

Jeez here I was thinking my phone just measures three different boops from giant radios in earth orbit. You've clarified GPS to be quite more complicated!

Splendid video, great content, very well presented tothe very highest technical standard. A delight to come across. Thank you for your efforts.

@CasualNavigation

5 жыл бұрын

Thanks Dick. Glad you enjoyed the content.

In an old GPS Navigator I had, I think there was a geodetic correction I had (or could) apply. Am I mistaken?

0:10 Trilateration uses distances, triangulation use angles.

@Bendigo1

Жыл бұрын

What uses angles AND distances???

Is differential gps still used in plane tracking apps?

Excellent presentation: direct , progressive , and with clear graphics. As an operator, I needed to get a handle on the 'nuts and bolts' of how it works. Thank you. Very well done.

@CasualNavigation

5 жыл бұрын

Thanks postwar46

0:12 - Trilaterates, not triangulates. 3:02 - Typo. 5:17 - Not if your GPS receiver is a civilian model. Civilian GPS devices only use one frequency. Also, DGPS signals are now also transmitted from geostationary satellites, in systems known as Satellite-Based Augmentation Systems, such as WAAS and EGNOS. These systems are meant to improve GPS performance in aviation applications. Another source of GPS positioning errors happens to be the rotation of the Earth, manifested in something called the Sagnac effect.

@danielthomas9086

3 жыл бұрын

"Civilian" psudeo-range GNSS receivers can use the L1 and L2C bands on the GPS system (that's 2 not 1); phase based systems (such ones used by land surveyors) use all the transmitted bands. If you are substituting the word GPS for GNSS then "civilian" psudeo-range receivers can use 2 bands from GPS, 2 from GLONASS and 3 from Galileo (of course if you live in the others parts of the world there are BeiDou, QZSS and IRNSS bands that can be used as well)

Very good explanation.

Great job. Thanks ❤

This video is the best one that I have seen that explains GPS for lay users. As Im neither a physicist or a professional navigator it is little relevance to me as to how relativistic effects affect the GPS. All I need to know is that they exist and the receiver compensates for them. Another great video. REQUEST: How about an update to cover GNSS.

i have a research to do on the subject, does anyone have more related articles or books that can help find more information.

Super super Thanks a million

That was better than any other gps vid I’ve seen. Generally I want to punch the screen. Not this time. Btw, few handheld GPS receivers are capable of dual frequency reception. SPS (standard positioning service) by L1 only is normal. L1/L2 receivers are quite a bit more expensive. (I use gps phase differential relative baseline I geodetic surveys.)

very good job

How quickly satellite locations are changing and how many in total are in service?

Link you provided in the description is not working.

3:39 How exactly would the receiver figure out the distance between it and the satellites by adding a third satellite? Given that the offset is unknown, that part is difficult to visualize. Also, how does the receiver know what T=0 is? I’m guessing the satellite sends the time when the transmission was sent? This is at great video, thank you!

why i cant use GPS in polar water? thanks

Great video

Subscribed... 🔥 🔥 🔥

But wouldn't it mean that time runs slower on a satelite compared to earth? If the speed of a vehicle comes closer to lightspeed, it slows down it's interior time, doesn't it? Or is this due to less gravitational pull from the earth?

@CasualNavigation

5 жыл бұрын

Time does run slightly slower on satellites. It is to do with the relative speeds between the observers. You can assume the observer on earth is stationary, so the satellite has a relatively high speed

@stephenolan5539

5 жыл бұрын

There are people who deny Einsteins Theory of Relativity. But GPS would not work correctly if it was wrong because his theory is used in the calculations and the time dilation is accounted for. If it did not exist then those corrections would make the GPS incorrect.

@XxZeldaxXXxLinkxX

5 жыл бұрын

@@CasualNavigation There is a time dilation effect due to the differential in height as well. Both speed and gravity contribute to this effect. Source : undergrad degree in physics

@Lucius_Chiaraviglio

4 жыл бұрын

@@CasualNavigation The video has an editing error -- it says that time runs faster on the satellites due to their speed, whereas their speed would make it run slower. BUT, being not as deep in Earth's gravity well makes their time run faster. So which effect is greater?

Great 👍 thanks 🙏

It is not triangulation, it is trilateration. This is a big mistake and commonly misunderstood

@koharaisevo3666

3 жыл бұрын

In this case it's multilateration 'cause there is more than 3 stations.

@tommydickens4617

3 жыл бұрын

Pretty sure it is triangulation; the distances are measured using time and speed. Trilateration uses signal strength to determine distance.

Worth mentioning that the satellites know their positions because the reverse is happening with ground stations broadcasting their locations to the satellites.

@terrydouglas5008

3 жыл бұрын

The satellites know their position because they keep track of their own movements and every so often a ground radar station verifies it's location and a controller at Schriever AFB . This guy does not know how the system works his explanation is way off!

@traceythomas6761

2 жыл бұрын

@@terrydouglas5008 Actually, its more of the latter (ground station uploads) than the former. While the satellites can propagate their ephemeris and predict their own position, in practice they are rarely allowed to use those results to ensure tighter operational control of the accuracy. There were studies and design trades about adding range finding hatdware and techniques, but the benefits and gains didn't outweigh the costs and risks.

@terrydouglas5008

2 жыл бұрын

@@traceythomas6761 I worked in the GPS operation center at then Falcon now Schriever Space Force Base. The operators on a set time table update the satellites positions with data received from NORAD. It was my job to maintain the two way link with the satellites. Each satellite has two three transmitters and one receiver. One channel receive/transmit is used for satellite updates.

@traceythomas6761

2 жыл бұрын

@@terrydouglas5008 I'm not sure we're disagreeing with each other. The two-line elements are indeed calculated on the ground, just as you say, and uploaded as a broadcasting script rather than letting the satellites carry on with their own internal calculations. So even though the satellites are capable of propagating their positions for long periods (and there was a largely unused capability to let them range against each other using crosslinks), the schedule you cite basically overwrote that need. If I recall, the tempo for uploading ephemeris usually meant the next upload happened before the old set reached the "end of message", unless that tempo changed, so the broadcasts are/were basically canned. I was on the GPS Block IIF space and ground design team around the same era as the transition from Falcon to Schriever and have been on site for work with the operators in 2SOPS many times. Maybe we worked together.

which formula/method is used by GPS to calculate Altitude of a airplane??

@Linusgump

2 жыл бұрын

The same one he explains. For a given time traveled from the 4+ satellites (there are usually at least 5 used to verify accuracy) there is only 1 location near the surface of the earth where all of the signals cross. Keep in mind, gps altitude has errors in it due to the variances in orbital distance of the satellites, and that’s why you still need a static altimeter set to the correct barometric pressure.

@gurpreetgagan5596

2 жыл бұрын

@@Linusgump thank you sir

do ou know algorithm?... How reciever knows the total wave travel time...even though there is one way signal transmission?

@danielthomas9086

3 жыл бұрын

The wave emitted from the satellite is modulated, giving the name of the satellite, the time sent, non-precise position of the satellite etc

@lobo5727

3 жыл бұрын

@@danielthomas9086 thankyou but gps module doesn't come. With etc... Still didn't get

@stevencolborne6845

2 жыл бұрын

As stated tje sat signal is always saying what time it is. And also contains modulation data with satellite orbital predictions. The modulated data is a slow transfer so may cause an initial delay before a solution is computed.

Great video, but the link is broken.

Time ticks slower for a fast moving object. Otherwise, good video.

My mind still gets boggled that the piece of glass, plastic, metal, silicon etc, aka a phone that I'm holding in my hand, can communicate all the way to a Satellite in orbit very far away It's amazing, and mind boggling

@traceythomas6761

2 жыл бұрын

While true of your phone, if that call is routed through a satellite, its not so much for GPS. For the latter, you're just picking up a widely available standard signal. The satellites don't receive communication from civilian receivers and have no idea you exist, much less that you're using their data to determine your position. Think of them like orbital lighthouses.

@Bendigo1

Жыл бұрын

Unless you are using a sattelite phone, it is not getting any signal from any sattelite. Any position that you get from the phone, such as on Google maps, comes from cellphone towers not gps.

@sissyfus6181

2 ай бұрын

@@Bendigo1" it is not getting any signal from any sattelite. " Totally wrong.

7:34 This is VERY wrong. Just due to the speed the clocks are running SLOWER on the satellites... but then you need to mention mention gravity, which you missed completely, because they are in slightly lower gravity the clocks run faster. So you have to add both effects up and constantly adjust for it. I think it drifts off about 10 km a day cumulatively. There's an office in the US military that all they do is compensate for this all day

super smart technology🌍

I often have 7 satellites acquired for high altitude kite flying. We have the World altitude record at 16,009 ft. above ground level. I use 3 different GPS units.

A few missing bits which are military but on the whole good video 👍

Wow, we are not worthy! There are so many smart people in this world.

How does the GPS know where the satellites are? Do the satellites include their position when they broadcast the time, or does the GPS keep an almanac of where every satellite should be at all times?

@AltayHunter

3 жыл бұрын

Can GPS devices that have network access download the almanac from the internet, or do they rely on receiving it directly from the satellites? Also, is there one almanac per satellite or does each almanac have data on the whole constellation?

nice thanks

Thanks

Nice Video

Speed of light or speed of sound? Sound makes more sense to me if its using radio waves

@H3CL

2 жыл бұрын

Radio waves move at the speed of light, imagine the time it would take to get information if those waves propagated at the speed of sound.

Lovely

How does the satellite know it's location??

Great and informative video, thank you. FYI: There was a brief time after the USA went to war against Afghanistan / Iraq following 911 that Selective Availability became a issue again due to the USA limiting access to GPS satellites, in preference of military application requirements. Industrial scale mines in South Africa, and elsewhere, are dependent on GPS data to control the movement of massive earth moving equipment around the mines, and during the period after the initial invasion by the USA they were only picking up three GPS satellites that were available for location data.

Can someone please explain who this man is? Is he a scientist or doctor? My lord the knowledge is never ending. I'd like an answer please.

What's with blurry blobs representing buildings?

so sat nav is always right not the wife directions now i got to tell her

@MenacingPerson

3 жыл бұрын

it just tells you where you are, not where you go. But if you use google maps you should be fine

@vyl4650

3 жыл бұрын

@@MenacingPerson except that one time it leads you over small roads, through tiny villages where the road is just broad enough so you don't scratch the paint and you end up in front of the chicken-coop of an old french lady because the road doesn't exist since ten years ago anymore

@aahillakhani399

3 жыл бұрын

@@vyl4650 oddly specific. bad experience?

@vyl4650

3 жыл бұрын

@@aahillakhani399 well it was somewhat annoying but also pretty funny. It was like one of these scenes in a movie. Parking in front of the coop, turning of the car and looking at each other in amused confusion. Honestly one of the best memories from that vacation

Talk about one Satellite, It look like we thraw a rock in to a cave, it will response an echo and we will count the time to calculate the deep. But some body please explain me how Smartphone or Satellite know the that time signal came? (because I think the Smartphone is unable to send any signal back to Satellite)

@pritam9645

3 жыл бұрын

Yeesss, I have sammmeee doubtt!! Please somebody respond!

Isn't the resistance to the signals by the (different layers of the) atmosphere always the same so you can subtract it!?

If the receiver's battery is depleted its clock will stop working. If the battery is recharged later the receiver will work again, but its clock will no longer be synchronized with the sitellite's clocks. How do receivers synchronize their clocks with satellite's clocks?

@tgstudio85

3 жыл бұрын

So you are saying that you are an idiot that’s why satellites are fake?

@jugosever

3 жыл бұрын

@@tgstudio85, I never said satellites were fake. They are real. My question was about GPS receivers.

@nounoufriend

3 жыл бұрын

Its the fourth satellite as 3 give you fix with error induced by local clock fourth then is then able to calculate basically your exact moment in time from the error . If we had atomic clock synchronised on our receiver then we would get fix with only 3 satellites but we can't

I left Endomondo ON after I came home and after 4 hours I did 5 kilometers and burned 600 calories.

Thank you

I expected the potential errors to include something about the weird shape of the earth (distorted sphere, slightly ovaloid, if I remember correctly).

@jericho86

3 жыл бұрын

GPS positioning measurements don't give you direct lat and longs. They give you xyz coordinates in a 3D grid that are then projected onto an ellipsoid (the mathematical model of a squished sphere), and are converted to lat, long, and height above the ellipsoid.

Correction: gps do not work on triangulation rather trilateration method.

@verlecox232

3 жыл бұрын

Multilateration for aviation gps because we need 4 stations minimum to shoot a LPV approach

I still don't understand how "a" (the time error) is calculated

The video totally screws up the relativistic effects. It ignores General Relatively entirely even though it causes (due to reduced gravity) the greatest deviation on satellite clocks (+46 microseconds per day). The video only mentions the effects of Special Relatively (-7 microseconds daily due to satellite velocity). The SR high velocity makes the orbiting clocks "SLOWER", while GR low gravity makes orbital clocks run "FASTER." The GR speeding is about six times that of SR slowing, producing a net value of about +39 microseconds which is why orbital clocks are programed to run slow by this amount.

Ok you need to stip eith using logoes in ur examples its getting snnoying with the blurry stuff

Woooow

Darn you, Algebra 😠 turns out there is a real practical use for you

@Taffy064

4 жыл бұрын

Absolutely! Darn you Algebra! Thankfully we have clever people to calculate all of this for us. So my time in school giving laxatives to the girls and getting bullied by the aforementioned females was not totally wasted.

It's actually not a ring but sphere

Trilateration not triangulation.

@pritam9645

3 жыл бұрын

How does the satellite knows that the receiver has received the signal?

Its important to remember that time is more flexible than most people realize. Two people on different latitudes will arrive at the same longitudinal point at the exact same time, but travelled different distances to get there. Imagine someone 1 meter from the south pole and someone on the equator. The variable allowing for both to arrive at the same time is time itself being experienced differently in relation to their velocity. Also, and not mentioned in the video (or I missed it) is the impact of gravity on time. The Earth is not a uniform push down on everywhere. The push down can be different over certain spots versus others depending on what is in the ground etc.

I'm sure you already know what GPS is. But have you ever wondered how GPS is? Everyone always asks what GPS is but no-one asks how GPS is... XD

The one good thing that Bill Clinton did was to order the selective availability turned off on May 4 2000 (from memory). When I heard the news on the TV I went outside with my ancient Panasonic G5500 - only takes 20 minutes to get a fix - and was astonished to see the increased precision. I later bought a Magellan and had all the datum and transformation options, that really made GPS useful for everybody. We won't mention Monica....

Hi , I am Vaibhav K 3D Artist, we have more than 7+ years of experience in 3D. If you have any kind of 3d related work , please let me. Thanking you. Yours Sincerely, Vaibhav K

GPS uses trilateration not triangulation.

GPS is a ground based system LORAN (Long range hyperbolic radio navigation system) proved this decades ago with a ground range of up to 2400km no satellites required, obviously since WWII the infrastrcture and technology have improved and public GPS frequencies are open on all cell towers. the towers never move and that is how we get very accurate positioning on GPS enabled devices. cell signal and GPS are basically the same technology just running at different frequencies, the GPS frequencies are lower and travel further. obviously there are other factors such as the size and power of your hardware, satelite phones are just normal mobile phones but with better hardware designed to achieve greater range. obviously marine industry navegation tech is more powerful still.

@Bendigo1

Жыл бұрын

No.

@XPLAlN

Жыл бұрын

@@Bendigo1 ...and thrice no.

As far as I know speed of satellite orbit is irrelevant due to being way slower than speed of light. The relativistic effect that takes place is due to the curvature of space-time caused by the mass of the earth. Time is flowing faster for the satellite with respect to us due curved space-time. So the clock on the satellite are made to tick slower. Near relativistic speeds time flows slower for the moving object with respect to us. The clock on the satellite would need to tick faster.

WHo's here from Drone Pilot school?