1. A subterranean imaging apparatus comprising: an antenna array comprising a plurality of elements, the plurality of elements configured on a land-bases vehicle; and a synthetic aperture radar (SAR) system coupled to the antenna array and operable to: receive electrical signals from the antenna array; transmit electromagnetic radiation from a first subset of the plurality of elements to a subterranean target below a ground surface, wherein the antenna array has a depression angle selected to generate and transmit the electromagnetic radiation as air waves, lateral waves, and ground waves, wherein the lateral waves are bounded by the ground surface and a critical angle defined by an interface of the ground waves and the lateral waves; receive electromagnetic radiation reflected from the subterranean target on a second subset of the plurality of elements having a polarity similar to the polarity of the first subset, the electromagnetic radiation having a frequency that ranges from 0.1 to 2.0 Gigahertz; generate raw images from the electrical signals; generate a weighting according to phase statistics of pixels in the raw images; and combine the raw images using the weighting to generate a refined image of the subterranean target, wherein the antenna array is operable to generate the electrical signals according to the electromagnetic radiation reflected from the subterranean target, wherein the SAR system is operable to generate the raw images by combining a plurality of the electrical signals at differing positions of the antenna array relative to the subterranean target to determine a position of the subterranean target and positions of features other than the subterranean target below the ground surface.