An object-detection system comprising: a pair of neighboring ultrasonic sensors on a vehicle; and a device for executing instructions stored in a memory to implement a fusion module configured to: identify, using object-detection data from the pair of neighboring ultrasonic sensors on the vehicle, spatial intersections between arcs of ultrasonic signals of the pair of neighboring ultrasonic sensors, a spatial intersection comprising an intersection between arcs of ultrasonic signals that are generated at approximately the same time by the pair of neighboring ultrasonic sensors, the pair of neighboring ultrasonic sensors including a first sensor and a second sensor, the ultrasonic signals for the first sensor being modulated with one or more frequencies and amplitudes that are different than the ultrasonic signals for the second sensor; identify temporal intersections in the object-detection data between a current arc of a current ultrasonic signal and a previous arc of a previous ultrasonic signal of at least one sensor of the pair of neighboring ultrasonic sensors based on a movement speed of the vehicle; determine first range and angular information corresponding to an object relative to the vehicle based on the spatial intersections; determine second range and angular information corresponding to the object relative to the vehicle based on the temporal intersections; and generate a spatial-temporal fusion map that maps ultrasonic-sensor detections of the object relative to the vehicle based on the first range and angular information and the second range and angular information. a pair of neighboring ultrasonic sensors on a vehicle; and a device for executing instructions stored in a memory to implement a fusion module configured to: identify, using object-detection data from the pair of neighboring ultrasonic sensors on the vehicle, spatial intersections between arcs of ultrasonic signals of the pair of neighboring ultrasonic sensors, a spatial intersection comprising an intersection between arcs of ultrasonic signals that are generated at approximately the same time by the pair of neighboring ultrasonic sensors, the pair of neighboring ultrasonic sensors including a first sensor and a second sensor, the ultrasonic signals for the first sensor being modulated with one or more frequencies and amplitudes that are different than the ultrasonic signals for the second sensor; identify temporal intersections in the object-detection data between a current arc of a current ultrasonic signal and a previous arc of a previous ultrasonic signal of at least one sensor of the pair of neighboring ultrasonic sensors based on a movement speed of the vehicle; determine first range and angular information corresponding to an object relative to the vehicle based on the spatial intersections; determine second range and angular information corresponding to the object relative to the vehicle based on the temporal intersections; and generate a spatial-temporal fusion map that maps ultrasonic-sensor detections of the object relative to the vehicle based on the first range and angular information and the second range and angular information. identify, using object-detection data from the pair of neighboring ultrasonic sensors on the vehicle, spatial intersections between arcs of ultrasonic signals of the pair of neighboring ultrasonic sensors, a spatial intersection comprising an intersection between arcs of ultrasonic signals that are generated at approximately the same time by the pair of neighboring ultrasonic sensors, the pair of neighboring ultrasonic sensors including a first sensor and a second sensor, the ultrasonic signals for the first sensor being modulated with one or more frequencies and amplitudes that are different than the ultrasonic signals for the second sensor; identify temporal intersections in the object-detection data between a current arc of a current ultrasonic signal and a previous arc of a previous ultrasonic signal of at least one sensor of the pair of neighboring ultrasonic sensors based on a movement speed of the vehicle; determine first range and angular information corresponding to an object relative to the vehicle based on the spatial intersections; determine second range and angular information corresponding to the object relative to the vehicle based on the temporal intersections; and generate a spatial-temporal fusion map that maps ultrasonic-sensor detections of the object relative to the vehicle based on the first range and angular information and the second range and angular information.