There are several ways to get specific numbers into your program, say for latitude and longitude: You can write them in explicitly, you can put them in as definitions, you can put them in as initial values of variables, you can compute them, you can read them from standard input using scanf(), you can read them from a named file, or you can get them as ``arguments'' from the command line used to run your program.

For the viewing latitude and longitude, this last way is best.

In the C++ language, the main program can look like

main(int argc, char** argv)
{
   view_lat_deg = (argc>1) ? atof(argv[1]) : 0 ;
   view_long_deg = (argc>2) ? atof(argv[2]) : 0 ;
   ...
}

Explanation: argv is a list of strings (argc of them), of which the first is the name of the calling program [not needed here] and the rest are the arguments as strings. Thus the first argument is argv[1], as a string of characters even though for this program it represents a number. The atof() function converts this alphanumeric string to a floating number. (This function needs #include <math.h>, but you will already have included that line because of the sine and cosine functions.) The ?: expression says to use the given argument if it is present or 0 otherwise.