The purpose of the Data Uncertainty project is to improve on the guidelines for data confidence, specifically to build and improve on the guidelines presented in Chapter 8 of Guidelines for Open Pit Slope Design. The table “Target Levels of Data Confidence” in Chapter 8 of Guidelines has been much discussed and is seen as something that can be improved upon. It presents levels of confidence as percentages, by level of study, for four categories, Geology, Structure, Hydrogeology and Rock Mass, and an encompassing category called Geotechnical. The specific aim is therefore to quantify the level of confidence of the geotechnical information available at different stages of the open pit development and to provide a rational and formal way of improving the level of confidence of the geotechnical information as additional data is collected through successive stages of project development. Criteria will be defined to judge the adequacy of the quantity and quality of data at different project stages. It is intended to develop simple, practical guideline for use by the mining industry.