Finding Difference in Aerial Image Processing

Hi

I am trying to find difference between two images (reference and test image). The images have been taken at about the same height from the same camera and at the same time of the day. I am using SURF points and Affine geometric transform to align the images. Then i find the difference between them. But there is alot of unwanted difference. I tried different variations of reference image as test image earlier(by rotating, zooming, shifting the image) and the results were fine. But this particular case is not understood. Why these difference appear (difference in screen markings in two images such as compass and other texts is understood. Position difference in trucks on road is also understood).

[faheem ifti]

Waiting for Image Analyst or anyother guidance please

[KALYAN ACHARJYA]

-from the same camera and at the same time-

Two images captured using the same camera and at the same time, is it possible?

[faheem ifti]

Two clicks actually (time difference in a few seconds). Same time of the day mentioned because images captured at different times could have different brightness, shadows etc...