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Questions tagged [gps]

stands for Global Positioning System, a satellite based navigation system

80
votes
6answers
14k views

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 ...
73
votes
5answers
34k views

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 ...
39
votes
3answers
7k views

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,...
27
votes
10answers
74k views

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 ...
23
votes
4answers
4k views

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 ...
15
votes
1answer
2k views

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 ...
13
votes
4answers
2k views

How does the GPS scale and deal with potentially millions of requests per second and respond in real time?

Nowadays almost everyone who have owned a smartphone or some type of GPS device somewhere. These devices also seemly update in real time. How is the GPS satellite capable of responding to potentially ...
13
votes
13answers
11k views

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 ...
13
votes
1answer
4k views

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 ...
11
votes
2answers
6k views

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 ...
10
votes
2answers
6k views

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 ...
9
votes
6answers
13k views

Resistors in series with Tx and Rx

I'm making my own board and using an ATmega 328 with the Arduino bootloader. I have a DIP switch to select either an FTDI chip (for programming) to be connected to the ATMega's Rx and Tx, or a GPS ...
9
votes
5answers
623 views

GPS for Cubesats - is 8km/sec too fast for consumer chips?

Satellites in low earth orbit are moving close to 8km/sec. Most consumer-grade GPS chips still invoke the CoCom limits of 1000 knots, about 514 m/s. CoCom limits are voluntary limits for exports that ...
9
votes
3answers
2k views

GPS Units - Weather Balloon

I have a problem concerning GPS units. I have been studying on a project for a weather balloon which will go about 30 - 40km up. Now I do know that some GPS units have a limit on how high they can ...
9
votes
2answers
3k views

Send GPS coordinates via VHF

I want to set up a system such that wherever a user of VHF presses the PTT button the coordinates from a GPS receiver will transmited to receiver and stored in a computer. Is that possible ? Where ...
8
votes
5answers
2k views

GPS QA during manufacturing

Testing and integration engineers on electronics.stackexchange How do you quality check if a GPS module and its subsystems are up to the mark during manufacturing? ...
8
votes
5answers
4k views

Is passive GPS retransmission possible?

Is it possible to passively pipe GPS satellite signals indoors via a waveguide, or 2 antennas connected by a coax? If so, with what type of waveguide, antennas, coax, etc. should I try and experiment?...
8
votes
4answers
3k views

GLONASS and GPS satellite usage simultaneously by Positioning Modules

Can a GPS module use 2 GPS satellites and 2 GLONASS satellites to obtain a fix without using all satellites of the same kind? I know that we cannot force this to happen but is it theoretically ...
8
votes
1answer
1k views

how is the 1PPS signal generated in GPS receivers?

The question might seem stupid, but the time of flight from the satellite is unknown and moving, the doppler effect is skewing the frequency (and is not constant due to the relative trajectory) and ...
8
votes
2answers
2k views

66 GPS channels for 22 satellites - why the factor of 3?

Modern GPS chips can use signals from many satellites at the same time to obtain a solution. While typically 4 are necessary, a larger number helps improve the solution with some types of errors. As ...
7
votes
2answers
2k views

Can I “integrate” the data from an accelerometer to record a motion trajectory?

I would like use an accelerometer equipped device to record a motion trajectory, as high-resolution and low-noise as possible. For instance, let's say I run a jogging route of 6 kilometres, returning ...
7
votes
2answers
338 views

Where does GPS interference such as that from Lightsquared come from?

A recent government test shows LightSquared products affected 75% of GPS receivers on adjacent frequency bands. Is this most likely because (a) the Lightsquared transmitters bleed over onto the wrong ...
7
votes
6answers
3k views

Reradiating antena for GPS

I need to test and maintain a batch of devices which contain GPS modules. I can work on the rest of the device, but when it comes to test the GPS part I have no signal on my desk, no matter how near I ...
6
votes
3answers
863 views

gps performance for synchronization

I can't understand why GPS reciever clock is very good (stratum 0). I know it's very accurate and pure within itself; but when it passes through a long distance wireless channel, then it has low power ...
6
votes
3answers
9k views

GPS Antenna | When is an Active Antenna really Necessary?

Many vendors provide positioning modules that support active antennas as well as ones that don't. I am using 4 positioning modules out of which 3 of them support active antennas and the other , CC4000 ...
6
votes
2answers
283 views

Tracking wandering vulnerable adults

I work in the field of telecare and advances are helping us keep the elderly and vulnerable out of residential homes/hospitals and allowing to retain their dignity and independence by staying in their ...
6
votes
1answer
98 views

GPS L5C Differential? Max Update Rate(bits/s|Hz)?

The differential GPS chips use L1 and L2C to calculate the ionospheric interference. With the new GPS satellites, the new band L5C is being deployed, and I am wondering about the following things: ...
6
votes
1answer
424 views

GPS Power consumption MTK3339 vs SirfIII for periodic logging application

I am currently working on redesigning a SirfIII based battery operated GPS logger. A MTK3339 based GPS module has been selected due to overall (advertised) performance. The GPS logger uses a ...
5
votes
2answers
827 views

How does GPS calculate time

How can a GPS device give exact timing even when the number of available satellites are zero? I'm monitoring GPS data using VisualGPS.
5
votes
2answers
19k views

Using a GPIO pin as a power source

I have an STM32F2 (reference manual here) which is connected to a GPS receiver through 5 pins. One of these pins is a power supply pin for the GPS. All pins on the micro-controller are GPIO pins that ...
5
votes
1answer
3k views

What is the major technological change that has dramatically improved GPS acquire time?

What has allowed us to go from a unit (eTrex for example in year 2000) that would take many minutes to acquire GPS lock and be unable to do so indoors, to a modern android phone that will lock in a ...
5
votes
2answers
8k views

How big a ground plane does a gps antenna need?

How big a ground plane does a gps antenna need? I am using a GPS puck antenna that has a magnetic base to hold it on to, typically, the roof of a car. I would like to use it from my room at home, on ...
5
votes
3answers
425 views

GPS Suggestions

I have decided to play in the world of GPS modules. I have read the GPS Buying Guide from Sparkfun, but still am not sure which unit I want to go with. I am leaning toward the LS20031, do any of you ...
5
votes
3answers
3k views

Inductor and capacitor for GPS antenna

I'm working with the Venus 634FLPx GPS chip. The reference schematic in the datasheetincludes an inductor L1 marked "optional biasing for active antenna": What ...
5
votes
4answers
151 views

Receive GPS Antenna and cable simple confirmation of operation

I am in need of testing a GPS antenna and cable assembly after installation at a reasonable cost. I have a GPS antenna installed on an airplane, then the coax cable from the antenna goes down to the ...
5
votes
1answer
2k views

GPS consideration for PCB with GSM (interference, setup etc)

I am working on a project which has a GSM and GPS on the same PCB (fairly near each other in an enclosure). Since I am not familiar with GPS I was wondering if any of you could give me some tips on ...
5
votes
1answer
1k views

How does the addition of a bias-t circuit affect the impedance of a transmission line?

I've got a GPS circuit where the antenna is connected directly to the GPS receiver via a coplanar waveguide designed for an impedance of 50ohms. Unfortunately, I neglected to add the bias-t circuit ...
5
votes
1answer
406 views

Why is it that the bandwidth of a patch antenna decreases with it's size?

I typically use a larger (25 mm) patch antenna in GPS/GLONASS receiver circuits. As you probably know, L1 bands for GPS and GLONASS are separated by roughly 25 MHz. For applications where I want to ...
4
votes
2answers
2k views

GPS update rate

My thought process: I i'm am looking for a GPS that updates fast enough to actually read its position traveling 130 miles an hour ( I did some math and think 5 times a sec up date rate would get me 17 ...
4
votes
2answers
2k views

Cheap bracelet with indoor location tracking

I want to provide people at an indoor exhibition of ours with a bracelet which allows me to send a signal to it to flash a led light. At the same time I want to be able to determine the location (...
4
votes
2answers
1k views

How to find whether a vehicle turned left or right or didnt turn using gyroscope data

We are trying trace a vehicle movement when the GPS goes down. We are using accelerometer and gyroscope sensors. And also get the vehicle speed from the OBD (dashboard.) The data will be collected for ...
4
votes
3answers
3k views

GPS positioning faster than 1Hz

I am a systems engineer working with various instrumentation devices for ground platforms. These platforms can vary in speed from 0-60+mph. Current instrumentation provides TSPI at 1Hz and is based on ...
4
votes
1answer
2k views

Help to understand/ explore small sized 3G and GPS Antenna Design

I recently came across an exciting device called Automile, from Sweden and what caught my eye is this - I am really impressed by the packaging and overall quality of hardware integration they have ...
4
votes
2answers
1k views

Garmin Gps Battery Modification

I recently bought a GTU 10 from Garmin. I want to extend it's battery life by replacing and soldering on a new battery and enclosing the battery and the GTU 10 in a 1601 Otterbox. I would like to be ...
4
votes
1answer
2k views

Suggestion for a GPS module with helical/omnidirectional antenna [closed]

I'm looking around for a decent GPS module for a project of mine. The Sparkfun GPS Buying Guide is nice, but focuses mostly on modules with patch antennae. My project is a wrist- or upper-arm-mounted ...
4
votes
1answer
674 views

How is impedance matching for chip antennas practically done?

I designed a PCB for a GPS tracking device and i want to further develop it to have a smd gps antenna mounted on the board. I know that for optimal signal transfer i need to design a matching circuit, ...
4
votes
2answers
11k views

Trying to build gps tracking device

I am an engineering undergrad trying to build one gps tracking device with features like live streaming, current position, average speed, etc. (and if possible then sound etc.) from some computer ...
4
votes
1answer
786 views

GPS accuracy problems outside vs inside with repeater

I have an interesting problem testing GPS receivers: While working inside our lab, we get reasonable results. We have a GPS repeater, as shown in the picture. Inside the lab, I get good accuracy (...
4
votes
5answers
2k views

Trouble in using MT3329 SKM53 GPS module

I bought a SKM53 GPS module a few months ago. I tried hard to make it work but couldn't get anything out of it. I was thinking it's a fault with the device (actually i thought i burned it by not ...
4
votes
1answer
256 views

GPS RX module Implementation

I have been tasked with designing a low power sensor system and the customer has decided location would be a great option. I have done GPS before but only with complete modules (Ant. + IC). To keep ...