1. A method for optically communicating, from a user to a laser tracker, a command to control operation of the laser tracker with steps comprising: providing a rule of correspondence between each of a plurality of commands and each of a plurality of spatial patterns; selecting by the user a first command from among the plurality of commands; moving by the user, between a first time and a second time, a retroreflector in a first spatial pattern from among the plurality of spatial patterns, wherein the first spatial pattern corresponds to the first command; projecting a first light from the laser tracker to the retroreflector; reflecting a second light from the retroreflector, the second light being a portion of the first light; obtaining first sensed data by sensing a third light, the third light being a portion of the second light, wherein the first sensed data is obtained by the laser tracker between the first time and the second time; determining the first command based at least in part on processing the first sensed data according to the rule of correspondence; and executing the first command with the laser tracker.