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Wrong longitude for mouse location across dateline

#1

I noticed when using the wrapdateline mode the X values go past -180 and 180. To fix this I used:

if (x < -180 || x > 180)
{
    x %= 180;
}

However, this doesn’t really work because once you go past 180 it should hit -179, instead it hits 181 which would give 1 using the formula above. I feel like this is something that should be figured out automatically when using the wrap mode.

Any ideas?

Drawing a line across the dateline in wrapping mode
#2

Hi Dan,

Do you think this function works for you?

    private int convert(int value)
    {
        if (value < -180 || value > 180)
        {
            value += 180;

            if (value < 0)
            {
                value %= 360;
                value += 180;
            }
            else if (value > 360)
            {
                value %= 360;
                value -= 180;
            }
        }

        return value;
    }

Regards,

Ethan

#3

Thanks Ethan.

Was able to shorten it down a bit by using the following:

((x + 180) % 360) - 180

also works for Latitude if anyone needs it

((y + 90) % 180) - 90

Note: Because modulus doesn’t work properly with doubles/floats all the time, you’ll want to use this or something similar:

double xRemainder = (worldPoint.X + 180) - (Math.Floor((worldPoint.X + 180) / 360) * 360);
double x = xRemainder - 180;

#4

Hi Dan,

Thanks for your share.

Any question please let us know.

Regards,

Ethan