GPS delay of around 5 ish seconds

Other Hardware Sensors
1 
#include <TinyGPSPlus.h>
#include <SoftwareSerial.h>


#include <Wire.h>
#include <LiquidCrystal_I2C.h> 

LiquidCrystal_I2C  lcd(0x27,20,4);

static const int RXPin = 4, TXPin = 3;
static const uint32_t GPSBaud = 9600;

// The TinyGPSPlus object
TinyGPSPlus gps;

// The serial connection to the GPS device
SoftwareSerial ss(RXPin, TXPin);

float average = 0;
float Alpha = 0.3;
float speed;

long start = 0;

void setup()
{
  Serial.begin(9600);
  ss.begin(GPSBaud);

  
  lcd.init();
  lcd.backlight();
}

void loop()
{
  
  
  speed = gps.speed.kmph();
  average = average  * (1-Alpha) + speed * Alpha;
  Serial.print(average);

  if (millis()-start>=1000){
    lcd.setCursor(0,0);
    Serial.print(" -------- Dis: ");
    Serial.print(average);
    Serial.print("--------");
    lcd.print(average);
    start = millis();
  }  
  Serial.println("");
  
  smartDelay(100);

  if (millis() > 5000 && gps.charsProcessed() < 10)
    Serial.println(F("No GPS data received: check wiring"));
}

// This custom version of delay() ensures that the gps object
// is being "fed".
static void smartDelay(unsigned long ms)
{
  unsigned long start = millis();
  do 
  {
    while (ss.available())
      gps.encode(ss.read());
  } while (millis() - start < ms);
}

when trying this code outside, when i start walking it takes 5 seconds to display a speed of 2-3 ish kmph instead of .3-5. It is a neo6mv2 gps, and i set it to 5hz in the u center application because i need that accuracy for the project i am working on. Does anybody know why it takes so long? Note, the serial also writes 9 ish messages per second.

2

The speed is determined from distance between successive locations divided by time, and is not very accurate if walking. The sensor probably uses smoothing or averaging over a period of several seconds to produce reasonably stable estimates.

3

I imagine that your expectations of responsiveness and accuracy may simply be unrealistic.

1 Like
4

Well, if you remember, speed is computed as the distance moved in a certain time. How often does your GPS return a change in distance?

5

ohh, idk why i thought it used the dopler effect to measure speed, so that why i thought it would be a real time speed. do you know i can make it use the doppler effect or am i just wrong in that regard

6

How do you see that working using satellites so far away you cannot see them?

7

I have never heard of using "the dopler effect" to get real time speed in a low end consumer GPS module. Please eludicate.

8

Doppler also has issues with accuracy, depending on conditions. It can also experience large jumps, so is filtered to get a smooth average. I would expect low end units could use both location delta and doppler to derive a speed, but that does not mean all low end units do.

The bottom line is that neither GPS location nor speed is as accurate as people think it might be.

9

i think i read it somewherwe, the other comment also believes it, thanks for replying

10

when going around 3-5 m/s, how accurate would it be? and would the accuracy be a random deviation of -0.2 to 0.2 m/s or something?

11

Good luck with your project. I expect you'll need it.

12

is that meant pasive agressively? or am i understanding wrongly

13

thanks if its npot

14

Thanks for the reply!

15

Honestly I have no idea. There is not much research on the subject; there are not many applications were people need to accurately measure walking speed.

However, I did find the following paper:

16

Test it by timing yourself, while walking a straight line at constant speed for a known distance d.

Average velocity = d/t.

17

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