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Questions tagged [gps]

Questions regarding the Global Positioning System's satellites and uses.

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GPS - correction of individual satellite time

I have been trying to calculate the satellite position using the Clock, Ephemeris and Integrity data. For satellite time correction, I need Tsv, and ToC for the calculation but I couldn't find the ...
SAG DAG's user avatar
2 votes
0 answers
41 views

Add small extra gps antenna on tracker installed inside aluminum tube [closed]

I would like to install a GPS tracker inside a scooter. Will the GPS signal will be lost if I install the tracker inside the vehicle? Can I add a small extra antenna to fix outside the scooter?
Marc D's user avatar
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-1 votes
1 answer
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What is the slantRange of a GPS

How can I know the slantRange of a GPS in the aer2ecef function thanks
TThoye's user avatar
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40 views

How can I calculate GPS satellite's Latitude and Longitude if I have the elevation, the azimuth, the XYZ coordinates of the ground station

How can I calculate a GPS satellite's latitude and longitude if the elevation, the azimuth, and the XYZ coordinates of the ground GPS station are provided? I have tried these questions: Computing GEO ...
TThoye's user avatar
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1 answer
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How can I calculate GPS satellite's Latitude and Longitude if I have the elevation and the azimuth

Please tell me how I can calculate a GPS satellite's latitude and longitude if I have the elevation and the azimuth angles. I am using a septentrio GPS receiver. Thanks
TThoye's user avatar
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1 vote
1 answer
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How to download (Assisted GPS) AGPS file on PC?

I am trying to implement GPS receiver in software. Can I use AGPS file for faster locking of GPS satellites? I read somewhere that EPO files exist for Assisted GPS but I can't find any place to ...
Kanika's user avatar
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2 votes
1 answer
96 views

If the pseudorange is not fixed, how does a receiver lock/fix onto a satellite signal?

If the satellite moves around the orbit at a velocity, the pseudorange between the receiver and the satellite should be changing right? If so, how does a receiver lock onto a satellite signal if the ...
newlearner's user avatar
1 vote
0 answers
121 views

How is the GPS signal transmission time encoded in the GPS signal?

I am trying to really understand how GPS works, to be able to "explain it to my grandma" level of understanding. One key aspect that I can't find an answer to is: how is the GPS signal ...
largehadroncollider's user avatar
2 votes
1 answer
104 views

GPS SV velocity mismatch

When using classic Newton's second law we have $$ \vec{F} = m \vec{a} $$ $$ \vec{F} = G \frac{M m}{r^2}{e_{r}} $$ $$ \vec{a} = \left( \frac{d^2 r}{dr^2} - r \left( \frac{d \phi}{dt} \right)^2 ...
Łukasz Więcaszek's user avatar
2 votes
0 answers
224 views

Time parameters in RINEX navigation file

Currently, I am trying to determine the position of a GPS satellite from a RINEX navigation file. I am using RINEX 2.11. Tables A3 and A4 describe how navigation files are structured. In order to ...
alex05's user avatar
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How does "onboard GPS" suggest "escalation speed and severity of a storm caused atmospheric drag to increase up to 50 percent"?

Engadget's says: A recent batch of SpaceX’s Starlink internet-beaming cubesats met with tragedy on February 3rd when a 49-member cohort of the newly-launched satellites encountered a strong ...
uhoh's user avatar
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2 votes
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58 views

What is the difference between SBAS and PPP used in GNSS accuracy corrections?

I've found that Satellite Based Augmentation System uses reference stations to compute a model for correction and send them via a master station to a geosynchronous satellite, then to GPS receiver. I ...
Yahya Aouled Amer's user avatar
2 votes
2 answers
165 views

Why using internet connection speeds up the GPS positioning? [duplicate]

I noticed that when I activate my cell phone internet connection, I get my GPS position much faster. What does the internet connection provide for the GPS receiver ?
Yahya Aouled Amer's user avatar
2 votes
1 answer
224 views

What is "Time To First Fix" in GNSS?

I used an app to test GPS, that shows me TTFF is equal to a few seconds. I want to understand : What is Time To First Fix? Is having internet access useful to improve it?
Yahya Aouled Amer's user avatar
1 vote
1 answer
58 views

Is Satellite Based Augmentation System ,used in GPS, a Differential Technique?

I've read that to get a higher accuracies in GPS, we use differential positioning techniques which compute for satellites errors, using well-known position base station. I want to know if the ...
Yahya Aouled Amer's user avatar
2 votes
2 answers
86 views

Does using multifrequencies totally eliminate the ionosphere delay on GPS measurements?

I've read that the GPS receiver computes the difference in measurement for two GPS satellite signals (in two frequencies L1 and L2), in order to compute the actual delay that the ionosphere causes. ...
Yahya Aouled Amer's user avatar
32 votes
8 answers
10k views

Why does GPS need the fourth satellite?

I am currently working on a GPS project, so I am doing some research about the subject. I understand that the GPS receiver knows its location by calculating its distances from 3 satellites, and by ...
Yahya Aouled Amer's user avatar
4 votes
0 answers
115 views

How do you compute horizontal coordinates of a GPS satellite from its broadcast ephemeris?

I'm not an astronomer by any means, and am trying to extract the horizontal coordinates, azimuth and altitude, of a GPS satellite given its most recent broadcast ephemeris. Here is some example ...
Matthew Trotter's user avatar
15 votes
2 answers
1k views

How can cosmic ray muons be used to replace GPS for positioning information in 3D on Earth and underwater?

Task & Purpose's The Navy is testing a GPS-like device that doesn’t require satellites “The future is extremely bright for this line of research." begins: The Navy is researching a new ...
uhoh's user avatar
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3 votes
0 answers
155 views

Why does this "satellite antenna at the Laguna Peak Tracking and Injection Facility" look so weird? (two dishes back-to-back)

The video 1967 Navy Satellite Navigation training film (IBM 7094 data center) after 11:57 (older version here) the narrator says: For every pound of satellite in ...
uhoh's user avatar
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4 votes
1 answer
274 views

Can the James Webb Space Telescope's position be determined using GNSS? And if not, how is this done?

As far as I know, the recently launched James Webb Space Telescope will be positioned at 1,500,000 km of the Earth, orbiting Sun-Earth L2 Lagrange point at roughly 4x the distance between the Earth ...
swiss_knight's user avatar
3 votes
0 answers
129 views

Are LHCP L-Band antennas for Cubesats available?

I am designing a cubesat to carry out GNSS reflectometry or GNSS-R. To collect the earth reflected signals, I need a nadir pointing array of patch antennas, with Left Hand Circular Polarisation (LHCP) ...
Luke O's user avatar
  • 31
5 votes
1 answer
273 views

Why end-of-life GPS satellites given orbits that seemingly still intersect active satellite orbits but with a different period? Recipe for disaster?

This answer to Where are MEO satellites put at the end of their operational life? says (currently in full): This is an active area of research. As you noted, the main satellites that are in MEO are ...
uhoh's user avatar
  • 149k
7 votes
2 answers
628 views

How is the ambiguity in code phase resolved in GNSS code-based positioning?

For positioning using GNSS, a typical introduction text (example PDF) introduces the concept of pseudo ranges as roughly being the time between transmission of a GNSS signal by the satellite $s$ and ...
Ludo's user avatar
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4 votes
2 answers
2k views

Ephemeris time and clock corrections in RINEX navigation files

RINEX (Receiver INdependent EXchange format) is a set of file formats to distribute satellite navigation systems data, including GNSS. One of these standards, navigation files, provide positional ...
Rafa's user avatar
  • 1,636
3 votes
1 answer
49 views

generated error terms for positioning based on a pre defined target accuracy level

I would like to ask a question about accuracy level and precise point positioning or PPP. I'd like to design a system such that when the desired accuracy level is provided as an input, the ...
user42663's user avatar
3 votes
1 answer
140 views

Lunar satellite navigation system

Inspired by some questions: Are People Actually Serious About Mining The Moon? How to estimate that receiving GNSS signals Earth while orbiting the Moon will still provide locations to about 200 ...
Fred's user avatar
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3 votes
2 answers
258 views

Could a satellite use a Miniature Atomic Clock (MAC) to provide GPS services?

I've been investigating GPS satellites and I got curious about onboard atomic clocks. I found this following paper on the concept of a CubeSat GPS constellation using Chip-Scale Atomic Clocks, and ...
Bensas's user avatar
  • 193
3 votes
1 answer
117 views

Could a single CubeSat provide location services on another celestial body such as Mars? Could a constellation do it?

From my understanding, by having two satellites emit a signal simultaneously (carrying atomic clocks to achieve it), a ground device could measure the difference in times of arrival to determine its ...
Bensas's user avatar
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1 vote
1 answer
1k views

How to convert GPS time to TAI time to UTC time?

I had naively assumed that GPS time and TAI were the same thing until I saw this answer: https://space.stackexchange.com/a/22244/12508 I know that there are differences between Terrestrial Time (TT) ...
honeste_vivere's user avatar
2 votes
0 answers
75 views

Understanding the paper "Determination of Satellite Orbital Elements by Means of On-Board GPS Receiver and Its Verification" by Yoshiwo Okamoto et. al

I have been assigned with implementing the algorithm proposed in the paper "Determination of Satellite Orbital Elements by Means of On-Board GPS Receiver and Its Verification" by Yoshiwo ...
Karl Johan's user avatar
3 votes
1 answer
236 views

Precise timing using GPS

Looking at https://gssc.esa.int/navipedia/index.php/GPS_Navigation_Message and other websites, in order for a satellite receiver (which doesn't have other means of getting precise GPS time) to ...
Randy's user avatar
  • 33
3 votes
1 answer
150 views

Geolocalizing photographs on astronomical bodies

In Are pictures taken from ISS geolocalized? I was considering photos taken on the Moon by astronauts. How can I determine a photographer's position and lens direction? And further, since there isn't ...
david's user avatar
  • 253
4 votes
4 answers
295 views

Alternative to GPS navigation for vertical landing, especially on other planets

Is the GPS data reliable or meaningful only on Earth or below the geo-stationary Earth orbit? For GPS navigation, does a rocket has to fly below the geo-stationary orbit? If GEO is a physical ...
seccpur's user avatar
  • 1,175
2 votes
1 answer
245 views

Does Falcon 9's first stage use laser, radar or vision to assist landing? [duplicate]

Does Falcon 9's first stage use only GPS when it makes its vertical precision landing, or is it assisted also by radar or laser ranging or computer vision? If not, why not?
LocalFluff's user avatar
  • 26.8k
7 votes
0 answers
618 views

Are software defined GNSS (GPS) receivers legal under ITAR and other export regulations?

With the latest update to ITAR rules, it looks like covered GNSS receivers are defined as follows: (2) Global Navigation Satellite System (GNSS) receiving equipment, as follows: (i) GNSS receiving ...
Manuel Menzella's user avatar
4 votes
1 answer
207 views

How to estimate that receiving GNSS signals Earth while orbiting the Moon will still provide locations to about 200 meters of uncertainty?

IEEE Spectrum's Can Astronauts Use GPS to Navigate on the Moon? NASA Scientists Say Yes says: Kar-Ming Cheung and Charles Lee of NASA’s Jet Propulsion Laboratory in California did the math, and ...
uhoh's user avatar
  • 149k
7 votes
0 answers
249 views

Interpolating precise ephemerides of GPS satellites

My objective is to obtain at least a sub-meter position accuracy by interpolation of the GPS ephemerides. There is conflicting research outside, where some authors state that a simple Lagrange or ...
Samuel Low's user avatar
1 vote
1 answer
220 views

Two line element set

I was wondering where I could find the TLE of a satellite ( I am looking for CASSIOPE). I went into this link - https://www.n2yo.com/satellite/?s=39265 but it has only got the most recent updated TLE. ...
budding physicist's user avatar
8 votes
1 answer
272 views

What will the US government start to label its GPS spacecraft after SVN 99

GPS spacecraft are currently identified by their “Space Vehicle Number” (SVN) which now number 01 through 75. What will happen after 99 GPS satellites are launched? Is there any plan currently in ...
johnDanger's user avatar
30 votes
1 answer
5k views

Could a Falcon Heavy really put six GPS Block III satellites in orbit at the same time?

This answer says: GPS Block III satellites are being launched to replace failed or aging Block II satellites, which doesn't require launching more than one at a time. A Falcon Heavy could fill up ...
uhoh's user avatar
  • 149k
13 votes
2 answers
573 views

Why multiple GPS satellites are never launched on the same rocket?

From what I've read, GPS satellites have been always put in orbit one at a time. In contrast, Galileo (aboard Ariane or Soyuz) and GLONASS (aboard Proton) sometimes are launched at the same time. Is ...
jinawee's user avatar
  • 233
3 votes
1 answer
207 views

When going to Mars, how do you measure exact distances to determine course corrections?

When probes fly to Mars, they must adjust their trajectories multiple times during transit to ensure correct orbit insertion. They fire their small onboard rockets a little bit to do this. But how do ...
chyeaaah's user avatar
3 votes
2 answers
1k views

Delay-Doppler maps in space science

Maybe this question might be more physics related, but I've read about mostly in context of space science: What is a delay-doppler map (DDM)? I can find it in exploration of asteroids (e.g. (...
sequoia's user avatar
  • 311
46 votes
3 answers
9k views

What is GPS' 19 year rollover and does it present a cybersecurity issue?

The NPR new item and audio podcast The Global Positioning System Resets talks about a 19 year cycling of something in the GPS system, but it's not clear what it is. Every 19 years, the Global ...
uhoh's user avatar
  • 149k
2 votes
3 answers
893 views

Does GPS spoofing ever come from space? How are spoofings usually detected?

The BBC News article Study maps 'extensive Russian GPS spoofing' says: (GPS spoofing) involves the state using strong radio signals to drown out reliable navigation data, says non-profit C4ADS. The ...
uhoh's user avatar
  • 149k
10 votes
5 answers
12k views

What is required to make GPS signals available indoors?

GPS satellites don't transmit strong enough to reach indoors, through the roofs and walls of buildings, like cell phones do. GPS signals that enter buildings through windows are unreliable since they ...
LocalFluff's user avatar
  • 26.8k
1 vote
0 answers
68 views

GPS PPS stable signal [closed]

My question concerns the GPS NMEA reading data about PPS signal. Is there any way to know via software using NMEA that the GPS PPS signal provided by its outport is already synchronized with the one ...
peter's user avatar
  • 11
2 votes
1 answer
1k views

Do GPS satellites use the earth's magnetic field in any way?

There's a lot of speculation about how changes or flips in the Earth's magnetic field would affect us, our machines, and sea turtles. I'm curious about the GPS satellites themselves. In one way they ...
tedder42's user avatar
  • 840
1 vote
0 answers
75 views

Examples of both hardware and software GNSS recievers

I am writing an essay titled: Critically evaluate the positional fixing capabilities of current smartphone technologies for real world GIS data collection I am wanting examples of both hardware and ...
Tom Haywood's user avatar