In-situ observations on a moderate resolution scale for validation of the Global Change Observation Mission-Climate ecological products: The uncertainty quantification in ecological reference data

•Validation for satellite products requires ecological reference data (ERD).•Insufficient attention has been paid to ERD errors in previous validation studies.•We thus developed the practical uncertainty quantification method of ERD.•Careless choice of observation protocols results in large observation errors.•An optimal observation protocol was described for each plant type and phenology.