1. An apparatus, comprising: a plurality of disparate sensors configured for above-ground travel within a survey region and to evaluate a volume of earth of a subsurface; at least a first sensor of the plurality of disparate sensors configured to generate a first probe signal at a first frequency or first range of frequencies and to receive a first return signal from the subsurface in response to the first probe signal; at least a second sensor of the plurality of disparate sensors configured to generate a second probe signal at a second frequency or second range of frequencies and to receive a second return signal from the subsurface in response to the second probe signal; a positioning system configured to produce position data associated with a geographic position of each of the sensors; memory for storing the position data and sensor data associated with at least the first and second return signals; a soil sensor configured to measure a soil parameter within the volume of earth that influences a measurement of subsurface depth; and a processor coupled to the sensors, positioning system, and memory, the processor configured to detect underground utilities within the volume of earth using the sensor data, associate the sensor data with the position data for each of the detected underground utilities, determine a depth of each of the detected underground utilities using the sensor data and soil sensor data; and store the associated sensor, position, and depth data for each of the detected underground utilities in the memory.