Why do we declare constant lat and lon value

Question

static const double LONDON_LAT = 51.508131, LONDON_LON = -0.128002;

What does this mean?

https://github.com/mikalhart/TinyGPSPlus/blob/master/examples/FullExample/FullExample.ino

The above link contains the full example program of that line.

This line is from tinygps++ library for extracting the coordinates and displaying in a table format. I'm using arduino uno, GSM module and GPS module to extract the coordinates and transmit it as message. Can anyone explain what dies this constant value mean and why do we use this?

Answer 1

Static variables are allocated storage only once in a program lifetime The const keyword specifies that a variable's value is constant and tells the compiler to prevent the programmer from modifying it and you can't change const variable's value and i guess you know double is a data type that can save floating point numbers that line declare two variables with names LONDON_LAT and LONDON_LON and both of them are in one line and because london's latitiude and longtitude doesn't change the const keyword is used

also i guess because those variables are constants you can use #define visit https://www.arduino.cc/reference/en/language/structure/further-syntax/define/

Answer 2

It's a good idea to declare variables the strictest possible way. So if you don't intend to change the value of LONDON_LAT at runtime, declare it as const.

This allows the compiler to alert you if your code tries to modify it, and it often allows the compiler to optimize the code.