An environmental monitoring radar device (20a, 20b) includes a transmitting unit (21, 22), a receiving unit (21, 23), a spectrum generating unit (21), an azimuth computing unit (21), an environmental determining unit (21) and a position computing unit (21). The transmission unit (21, 22) transmits a combination of transmission signals which are modulated using a plurality of modulation modes. The environment determination unit (21) uses the degree of randomness of a frequency spectrum for the respective modulation modes to determine whether an environment is a complex environment. If the environment of the vehicle is determined for the at least one modulation mode from the modulation modes as the complex environment, the position calculation unit (21) removes at least one azimuth, which corresponds to the at least one modulation mode, from the azimuths which are respectively calculated for the modulation modes by at least obtain a target azimuth that is at least one of the remaining azimuths except the distant azimuth, and calculate a position of the vehicle based on the at least one target azimuth.
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