Problem resize the images using latitude and longitude of the edges.

So, in I got a task that needs me to resize the image based on the latitude and longitude of the top-left and bottom-right. My formula is right here:

Code (CSharp):

1.  
2.     // Get width from the left and right lattidue
3.     public float getHeight()
4.     {
5.         double radius = 6371.01;
6.  
7.         Quaternion q1 = Quaternion.Euler(longTopLeft, latTopLeft, 0);
8.         Quaternion q2 = Quaternion.Euler(longTopLeft, latBotRight, 0);
9.         print(Quaternion.Angle(q1, q2));
10.         double theta = Quaternion.Angle(q1, q2) * Mathf.Deg2Rad;
11.         return (float)(radius * theta);
12.     }
13.  
14.     // Get width from the left and right longitude.
15.     public float getWidth()
16.     {
17.         double radius = 6371.01;
18.  
19.         Quaternion q1 = Quaternion.Euler(longTopLeft, latTopLeft, 0);
20.         Quaternion q2 = Quaternion.Euler(longBotRight, latTopLeft, 0);
21.         print(Quaternion.Angle(q1, q2));
22.         double theta = Quaternion.Angle(q1, q2) * Mathf.Deg2Rad;
23.         return (float)(radius * theta);
24.     }
25.  

The problem is that the images will always be too small or too large, is there anything that I could adjust to make it work?