1. A system comprising: a radar unit configured to provide raw data from scanning an exterior of a structure, wherein the raw data from scanning is provided from multiple scan locations; and a signal processing and imaging module configured to: process the raw data into markers of interior locations of the structure; populate an image grid having a first axis and a second axis with wall-coordinate pixels estimated from the multiple scan locations; demarcate an interior wall of the structure from the wall-coordinate pixels by a line passing through the first axis at a fixed pixel location on the first axis and parallel to the second axis if the wall-coordinate pixels along the line satisfy a pre-determined criterion; and display an image of interior structural features based on the markers.