Understand uncertainty in map measurements
Find the main source of error before adding decimal places.
Precision is not accuracy
A result such as 12,345.67 m² can be calculated precisely from your points while still being a poor estimate of the actual land area. The number of displayed digits reflects formatting, not verified boundary accuracy.
Identify the largest uncertainty
Look for unclear boundaries, old imagery, coarse zoom, too few points on curves, incorrect coordinate systems and slope. A long boundary makes small position errors important. Check whether you are measuring the same feature consistently, rather than alternating between the centre and edge of a road or ditch.
Measure again
Repeat the measurement independently with a different point set. Compare the totals and inspect the sections responsible for the difference. This is a sensitivity check, not a statistically established confidence interval. Our synthetic benchmarks isolate point-density effects; real-world data can contain other errors.
Know when to stop estimating
Round the answer to a useful level and state what boundary or route it describes. Use better geodata, official records or professional surveying when a decision depends on small differences. No universal percentage error can be promised for a manually drawn map measurement.