Question

This question is asked multiple time’s, but i can’t get it working…

I’m working on an program that calculates the distance between two points, and the calculates the time an unit walks about it…

This is the simplefied version of what i need to do:

x = 24 
y = 23

Root of (24² + 23²) = 33.24 fields

33.24 x 30 = 997,2 minuts

997,2/60 = 16,62 hours
16: (60*0.62) = 16:37,2   
16:37: (60*0,2) = 16:37:12

So i’ve got this piece of code in C#, but it isn’t working:

first_town = "35|629";
second_town = "59|606";
snelheidUnit = 30;

string[] firstTownSplit = first_town.Split('|');
string[] secondTownSplit = second_town.Split('|');
int firstTownPart1 = Convert.ToInt32(firstTownSplit[0]);
int firstTownPart2 = Convert.ToInt32(firstTownSplit[1]);
int secondTownPart1 = Convert.ToInt32(secondTownSplit[0]);
int secondTownPart2 = Convert.ToInt32(secondTownSplit[1]);

int verschilX = firstTownPart1 - secondTownPart1;
int verschilY = firstTownPart2 - secondTownPart2;

double aantalVelden = Math.Sqrt((Math.Pow(verschilX, 2) + Math.Pow(verschilY,2)));       // Fields
double aantalMinuten = aantalVelden * snelheidUnit;             // Minuts
double aantalUren = aantalMinuten / 60;                 // Hours

TimeSpan time = TimeSpan.FromHours(aantalUren);
string FinalTime = string.Format("{0:D2}d:{1:D2}h:{2:D2}m:{3:D2}s:{4:D3}ms", time.Days, time.Hours, time.Minutes, time.Seconds, time.Milliseconds);      

The expected output should be: 00d:16h:37m:12s:772ms

But is: 00d:16h:37m:14s:772ms

The difrnce is 2 seconds. What is the bottleneck? Why is there 2 seconds difrnce between the expected output and the real output?

Answer 1

Root of (24² + 23²) = 33.24 fields

The square root of 1105 isn’t exactly 33.24; you only get 33.24 if you round the square root. So compare your problem description:

33.24 x 30 = 997,2 minuts

997,2/60 = 16,62 hours
16: (60*0.62) = 16:37,2   
16:37: (60*0,2) = 16:37:12

against what happens with a more precise value for the square root:

33.241540277189322804630581542105 * 30 = 997.24620831567968413891744626316 minutes
less 16 hours (960 minutes) leaves 37.246208315679684138917446263157 minutes
less 37 minutes leaves 0.246208315679684138917446263157 minutes
which gives 14.772498940781048335046775789394 seconds

which is about 2 seconds different from what you are getting

If you want to reproduce your original calculation, you need to do something after

double aantalVelden = Math.Sqrt((Math.Pow(verschilX, 2) + Math.Pow(verschilY,2)));       // Fields

to round that in the same way as your original; for example,

aantalVelden  = Math.Round(aantalVelden, 2);