How can a ship/tower crane measure the load that is being lifted? is there a measuring device incorporated in the machine? how does overload prevented or detected?
In my view using the actual crane to calculate the weight is a bad practice.
Once load is calculated the cranes can tell you the weight I am speaking for a modern crawler or Hydro crane, I would think a tower crane would have the same devices available.
If the load was caculated wrong there are bells and whistles indicating such, but sometimes that indication can come to late, caculate the load and when in doubt add to the weight, and of course alot can go into what it takes to calulate the weight, anlges distances etc.