stands for Global Positioning System, a satellite based navigation system
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Questions tagged [gps]
437 questions
85
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6 answers
Why does smartphone GPS find its position much faster than a GPS module?
When I'm using the arduino GPS module it usually takes a couple of minutes for it to start sending data. And it seems that it's usually the case with all GPS modules since they need to "listen" to the satellites for some time. However whenever I use…
Anthropomorphous Dodecahedron
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How many GPS channels make sense?
You need 4 channels to determine your position (including elevation), and I can understand that a few extra channels increase accuracy. However, there are maximum 12 satellites in view at any time, so why have receivers with more channels? I've seen…
stevenvh
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3 answers
How do GPS satellites refresh their clocks
How do GPS satellites keep their on board clocks accurate? I assume that they need to get update from a base station. But how do you make sure that after the update all the satellites are synchronized, i.e. there isn't any phase shift.
You have…
user110971
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39
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4 answers
How can a 9mm square antenna pick up GPS?
I'm confused again. Per various antenna dipole calculators online, and if GPS uses 1.575 and 1.228 GHz signals, the dipole antenna needs to be on the order of 10 cm. Yet Adafruit has (or had) tiny GPS antennas of about 9mm square. And there's the…
user3303210
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Why do GPS receivers have a 1 PPS output?
I was surprised to see that the GPS receiver I'm working with has a pin reserved for outputting a 1 PPS (Pulse Per Second) signal. What is the point of this? Can't the microcontroller easily generate its own 1 PPS signal?
Randomblue
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How can the GPS position update rate be 10 Hz?
Based on stuff on the web (Wikipedia and others) the GPS navigation message bit rate is 50 bit/s. That includes all data needed for user position calculation (time, ephemeris, almanac, etc.) It seems that the packet from a satellite should be much…
Alihaji
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4 answers
True GPS Location - At the Antenna or Receiver Chip?
Suppose I have a GPS unit attached to an antenna through a 50 meter coax cable.
How would the location as calculated by the GPS unit be affected by the cable length? As a bonus question, how would the time accuracy of the GPS be affected by the…
David Gardner
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15
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GPS Design Review (RF Input)
I've designed a PCB in Eagle to host a GPS Receiver module and a GPS patch antenna. The RF input to the module is specified as a 50Ω unbalanced (coaxial) RF input. I used this calculator to calculate the required width and spacing for a co-planar…
vicatcu
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How do receivers decode multiple GPS signals on the same carrier frequency?
I'm currently researching GPS signals and am trying to fully understand the path of a signal from satellite to receiver.
I understand that mixed into the GPS signal is a C/A code as well as a PRN which aids in the process of CDMA that the receiver…
Justanothermatt
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15
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Official GPS protocol documentation?
Searching for "GPS protocol" reveals many sources for processed GPS data, e.g. NMEA or binary outputs of GPS units.
Where is the official documentation for the GPS satellite - receiver protocol? Or any interesting supplemental material that might…
Mark Harrison
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14
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GPS pulse/s not aligned with reported times (u-blox ZOE-M8Q)
For the sake of fun and learning, I'm trying to make the most accurate wall clock I possibly can, driven by GPS. I'm starting with a u-blox ZOE-M8Q breakout board I got from SparkFun, and a Raspberry Pi Pico microcontroller.
At a glance, things…
Neil Forrester
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4 answers
How does a GPS antenna have only two connections yet have all this circuitry inside?
This GPS module I have broke (just gets hot and won't work) so I took it apart and am amazed to see all of this circuitry under the ceramic antenna but only two connections (gnd and signal). When tested there is ~3v between the signal and ground…
tavis
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What is the highest achievable update rate for a civilian GPS receiver?
I'm interested in knowing the maximum achievable update rate for a civilian GPS receiver. Specifically
Receivers that depend exclusively on GPS satellites (e.g. not including IMU-based movement estimation to interpolate)
The hypothetical limit (i.e…
user139772
13
votes
2 answers
GPS: 12 satellites in view but no fix
I have a Jupiter F-2 GPS receiver connected to an STM32 that outputs NMEA messages every second. The GPGSV message indicates that I have 12 satellites in view. At the same time, the GPGSA messsage indicates that I have no fix, either 2D or…
Randomblue
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What can I use to detect pinpoint location (inches) outdoors?
I am getting back in to EE after some time so please excuse my ignorance. I am looking for a way to detect pinpoint location outdoors to navigate a robot for a project with my sons.
Is there a low cost way to triangulate or use GPS? I am looking for…
Jamey McElveen
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