Google map in vb.net, lat/lon boundaries

[charlie363]

I am acquiring a google earth image in vb.Net using the following:

imgImage.Load("http://maps.google.com/staticmap?center=" _
                      + dblLat.ToString + "," + dblLong.ToString + _
                      "&zoom=" + intZoom.ToString + _
                      "&size=512x512&maptype=satellite")

where imgImage is a PictureBox .net object.
I need to know what the width and height of the image returned is in NauticalMiles. My understanding is that:
- ZoomFactor=1 means 360deg, which means 360*60NM
- ZoomFactor=2 means 180deg, which means 180*60NM
- etc.....
- ZoomFactor=5 should be equivalent to 1350NM

When I actually check this distance on GoogleEarth I get something closer to 1100NM from North to South and from East to West.
How can I get a better accuracy on the boundaries of my image?
By the way, I will be essentially working on large zooms (around 100NM resolution), so it's ok for me to ignore earth curvature.
Thanks for your help,
Charlie