The objective of field measurements is to define the operating conditions for in situ retorts. More specifically we would like to determine the optimum operating conditions for a commercial size retort. To reach this objective we will 1) collect data from a number of demonstration retorts, 2) predict optimum operating conditions using this data and the LLL retort model and 3) evaluate some of the potential difficulties for field operation. First we want to concentrate the measurement aspects: what should be measured, where it should be measured, and what is the value of each measurement. How to make these measurements, how to record data, and costs will be described in later sections of this paper.