Collection of the reference data for use in an accuracy assessment is a key component of any assessment. The collection of ground reference data is extremely expensive, and the collection effort must be sufficient to meet the needs of the accuracy assessment while being efficient enough to meet the needs of the budget. Accuracy assessment reference data should be collected as close as possible to the date of the collection of the remotely sensed data used to make the map. Trade-offs may need to be made between the timeliness of the data collection and the need to use the resulting map to stratify the accuracy assessment sample. An important mechanism for imposing objectivity is the use of a reference data collection form to force all data collection personnel through the same collection process. Forms provide a means of performing a quality assessment/quality control check on the collection process.