To assess the usefulness of a commercially available indoor positioning system for monitoring the resting time and moving distance in group‐housed dairy calves as indicators of their health status, five dairy calves were housed in a free barn, and their coordinate was recorded. The mean displacement (cm/s) within a minute showed a double‐mixture distribution. Actual observations revealed that the minutes in the first distribution with shorter displacement were mostly the time that the calves spent lying. To predict the daily lying time and moving distance, a mixed distribution was divided at a threshold value. The mean sensitivity (the proportion of total minutes predicted correctly as lying, in total minutes observed lying) was more than 92%. The daily fluctuation in lying time correlated well with the actual lying time (r = 0.758, p < 0.01). The range of fluctuations was 740–1308 min/day and 724–1269 m/day for daily lying time and moving distance, respectively. The rectal temperature was correlated with daily lying time (r = 0.441, p < 0.001) and distance moved (r = 0.483, p < 0.001). The indoor positioning system can be a useful tool for early illness detection in calves before the onset of symptoms in group‐housing systems.