Final answer:
The minimum number of positions that must be on all load charts for boom cranes is two: rated capacities and working area.
Step-by-step explanation:
In order to create a load chart for a boom crane, several key positions must be included. The minimum number of positions that must be on all load charts for boom cranes is two.
The first position is known as the rated capacities position. This is the maximum weight the crane can lift at a given radius.
The second position is known as the working area position. This shows the limits of the crane's safe operation, taking into account factors such as stability and structural integrity.