Answer:
- "instantaneous"
- sample the speed at regular intervals and compute the average
- use more samples and/or more regular intervals and/or use a weighted sum that approximates the curve between readings.
Explanation:
A speedometer is designed to give an approximation of instantaneous speed. It is an average over a short time interval, typically less than a second or two.
__
If you have only the speedometer as reference, you need to write down its speed reading on several occasions, roughly equally-spaced in time. The average of these readings will be an approximation of your average speed.
To get a better average, shorten the intervals and make them more evenly-spaced. You can also compute various weighted averages of these speed readings.
