Read, JRL 2013, 'Data gathering, interpretation, reliability and geotechnical models', in PM Dight (ed.), Slope Stability 2013: Proceedings of the 2013 International Symposium on Slope Stability in Open Pit Mining and Civil Engineering, Australian Centre for Geomechanics, Perth, pp. 81-89, https://doi.org/10.36487/ACG_rep/1308_0.5_Read (https://papers.acg.uwa.edu.au/p/1308_0.5_Read/) Abstract: The geotechnical model is the cornerstone of open pit design (Read and Stacey, 2009). It must be in place before the steps of setting up the geotechnical domains, allocating the design sectors and preparing the slope design can commence. The processes that must be followed to construct the model are outlined in this paper. They include recent advances in assessing parameter and model uncertainty, in particular, a modified Bayesian approach that has been developed to estimate the expected value of the measure of reliability. Overall, they form part of a system of reporting confidence in the geotechnical model and matching target levels of geotechnical effort with target levels of confidence in the data at each stage of project development.