A wheel alignment system comprising: a pair of first and second passive heads, each comprising a target (2200; 2500), for mounting in association with a first pair of wheels (103a, 103b) disposed on first and second sides, respectively, of a vehicle that is to be measured by operation of the wheel alignment system; a passive reference pod; an active reference pod comprising a reference image sensor (300; 2700) fixedly attached to a reference target (200; 2100), for mounting to a stationary reference at a location on the first side of the vehicle such that the reference image sensor (300; 2700), in use, produces image data including a perspective representation of the passive reference pod mounted to the stationary reference and comprising at least one target (210; 2400) disposed on the second side of the vehicle; a pair of first and second active heads, each comprising an image sensor (105a, 105b; 2000; 2300), for mounting in association with the first and second sides of the vehicle, respectively, the image sensor (105a; 2000) of the first active head, in use, producing image data including a perspective representation of the targets (2200, 2100) of the first passive head mounted in association with a first wheel of the first pair of wheels and of the active reference pod mounted to the stationary reference, and the image sensor (105b; 2300) of the second active head, in use, producing image data including a perspective representation of the targets (2500, 2400) of the second passive head mounted in association with a second wheel of the first pair of wheels and of the passive reference pod mounted to the stationary reference; and a computer for processing image data from the image sensors relating to the observations of the targets to compute at least one alignment measurement of the vehicle based on a spatial relationship between the active reference pod, mounted to the stationary reference, and the passive reference pod, mounted to the stationary reference, determined according to the image data produced by the reference image sensor. a pair of first and second passive heads, each comprising a target (2200; 2500), for mounting in association with a first pair of wheels (103a, 103b) disposed on first and second sides, respectively, of a vehicle that is to be measured by operation of the wheel alignment system; a passive reference pod; an active reference pod comprising a reference image sensor (300; 2700) fixedly attached to a reference target (200; 2100), for mounting to a stationary reference at a location on the first side of the vehicle such that the reference image sensor (300; 2700), in use, produces image data including a perspective representation of the passive reference pod mounted to the stationary reference and comprising at least one target (210; 2400) disposed on the second side of the vehicle; a pair of first and second active heads, each comprising an image sensor (105a, 105b; 2000; 2300), for mounting in association with the first and second sides of the vehicle, respectively, the image sensor (105a; 2000) of the first active head, in use, producing image data including a perspective representation of the targets (2200, 2100) of the first passive head mounted in association with a first wheel of the first pair of wheels and of the active reference pod mounted to the stationary reference, and the image sensor (105b; 2300) of the second active head, in use, producing image data including a perspective representation of the targets (2500, 2400) of the second passive head mounted in association with a second wheel of the first pair of wheels and of the passive reference pod mounted to the stationary reference; and a computer for processing image data from the image sensors relating to the observations of the targets to compute at least one alignment measurement of the vehicle based on a spatial relationship between the active reference pod, mounted to the stationary reference, and the passive reference pod, mounted to the stationary reference, determined according to the image data produced by the reference image sensor.