Definition
Estimated by reading between two known values on a chart, table, or graph to find a value that is not explicitly listed.
Plain English
Worked out by splitting the difference between two numbers that are shown, to get a number that isn't shown.
Context Anchor
Seen in compass-turn discussions when estimating how much compass error applies to headings between the main reference headings.
Derivation
From Latin 'interpolare', meaning 'to refurbish' or 'insert between'. The 'inter-' part means 'between', which is exactly what you do — you find a value that sits between two given ones.
Why Pilots Care
Performance and compass tables rarely show the exact temperature, weight, or heading you're working with. Interpolating gives a more accurate figure than just rounding to the nearest listed value, which matters for takeoff distance, fuel planning, and turn rollout headings.
Intuition Check
Interpolated does not mean guessed randomly. It means estimated between known reference points.
Example Sentence 1
The chart listed takeoff distances for 20 °C and 30 °C, so the pilot interpolated to find the figure for 25 °C.
Example Sentence 2
Because the deviation table listed only every 30 degrees, the pilot interpolated the correction for a heading of 255 degrees.