1

I use a u-blox gps with my arduino. I can successfully write out the value of a coordinate (lat, lng) like this: Serial.println (gps.location.lat(), 8); but when I try to store the value with all the decimals it returns 8.00 instead of the correct coordinate + all of the 8 decimals.

This is my code:

#include "TinyGPS++.h"
#include <SoftwareSerial.h>
SoftwareSerial gpsconnection (4,3);
TinyGPSPlus gps;

void setup()
{
 Serial.begin(9600);
 gpsconnection.begin (9600); 
}

void loop()
{
 while (gpsconnection.available())
 {
   gps.encode(gpsconnection.read());
 }

 //this works and returns 8 decimals
 Serial.println (gps.location.lat(), 8);
 Serial.println (gps.location.lng(), 8);

 //but if i try to store it like this:
 double latcord = (gps.location.lat(), 8);
 double lngcord = (gps.location.lng(), 8);

 //it returns 8.00 on both the "latcord" and "lngcord" which is the wrong coordinate and also it doesnt return 8 decimals
 Serial.println (latcord);
 Serial.println (lngcord);

 //if i try to convert the value to a string and then back to a double like this:
 double lat = gps.location.lat();
 String msgLat =  String(lat, 8);

 double thelat = atof(msgLat.c_str());

 //with this i get the correct first two numbers out but only 2 decimals after, not 8 decimals as it should be.
 Serial.println (thelat);

}
  • Note, accuracy of floats and doubles is the same on Arduino: 25 bits max, or about 7.53 decimals – James Waldby - jwpat7 Jun 13 '17 at 17:41
3

You forgot the , 8 from your println that specifies that it should print 8 decimal places. Instead you seem to have added it to the end of an assignment which makes absolutely no sense whatsoever.

double latcord = gps.location.lat();
double lngcord = gps.location.lng();

Serial.println(latcord, 8);
Serial.println(lngcord, 8);
| improve this answer | |
  • ah ok so i cant store the value (with the 8 dec) straight to a double, i have to give the dec afterwards. got it! thanks – Carlos Rodrigez Jun 13 '17 at 16:23
  • 2
    Floats and doubles don't have a fixed number of decimal places, that's not how they work. – Majenko Jun 13 '17 at 16:24

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