We try to build up a 3-dimensional image of a site using appropriate software. As new technology develops rapidly and the budget of the ADU is restricted, we often borrow equipment from suppliers and manufacturers, but when the cost-effectiveness equation suggests it would be a sensible option, equipment is sometimes hired. We try to assess new wreck sites without using any intrusive techniques wherever possible. The only reason for this cautious approach is that if a site is buried, exposing material for study will also expose it to degradation. Any intrusive activity such as excavation will generate chemical, physical and microbial activity, and may well seriously destabilise the site.
Archaeologists are no different to any one else.
We are curious and would often dearly love to know what is buried, but our training makes us appreciate the massive problems that excavation can bring.