A technique for identifying a measurement planned position for electromagnetic waves in a three-dimensional space in a simple and easy manner is provided. A position of a measuring unit 200 that is carried by an operator 100 is measured by a position measuring device that is configured to measure a position by laser light. A positional relationship between the measured position and the position of a measurement planned position 601 is displayed on a terminal 300 that is carried by the operator 100. This display guides the operator 100, and the operator 100 identifies the measurement planned position 601 and measure illuminance thereat.