Define interpolation.

• A. The act of guessing or estimating numbers not explicitly written on the load chart
• B. The process of reading all values exactly
• C. A method to convert loads to metric units
• D. The procedure for calibrating the load chart

Answer: (A)

Interpolation is estimating a value that lies between two known data points on a chart. In crane practice, load charts give capacities at specific boom lengths, radii, and configurations. If your operating point falls between those entries, you estimate the allowable load by interpolating between the adjacent data points, typically using a straight-line (or chart-supported) estimate. This keeps the estimate grounded in the chart data and helps avoid overloading by providing a reasonable, continuous value rather than a guess from nowhere. It’s about using the surrounding chart values to guess what lies between them, not about reading exact points, converting units, or calibrating the chart.