Haniyeh, It will not be time demanding, you can certainly do it using ATCOR quite quickly.

If the data set only covers a few degrees lat/lon and the changes in altitude are less than about a km, applying an atmospheric correction from a point in the center of the image should be good enough for nearly any purpose. If you have aerosol information that may change things, but the atmospheric correction is not a rapidly changing function unless you have steep topographic gradients.

My practical experience shows yes, you have to apply these corrections on the entire image no matter it is time consuming.