What Is Ground Penetrating Radar (GPR) and How Does It Work?
Ground Penetrating Radar (GPR) is a non-invasive scanning tool that fires high-frequency radio waves into the soil and listens for echoes. By timing and plotting those reflections, GPR creates a subsurface image that pinpoints underground objects, layers, or voids—such as marked or unmarked graves—without any digging or damage.
Ground penetrating radar sends a quick radio pulse, from 1 to 1000MHz, into the ground. When the pulse meets something different—air, wood, metal, or compacted soil—it bounces back. A small cart with a transmitter and receiver records these echoes every few inches as it rolls across the cemetery. Software turns the echo times into a side-view picture called a radargram. Graves show up as smooth, arch-shaped curves (hyperbolas). Because the speed of the pulse depends on the soil, technicians can work out the depth, often 8–10 ft or more.
Sentry Mapping pairs high-frequency GPR (250–900 MHz) with survey-grade GPS so each echo has an exact x-y location. After the field scan, we filter noise, stack overlapping lines, and build a 3-D model of the subsurface. The finished results feed straight into our digital cemetery mapping service and Chronicle cemetery management software. You receive a printed master map plus an online map that staff and visitors can search from any device—no digging, no disturbance, and no yearly fees. This professional cemetery mapping method finds every marked or unmarked grave, protects heritage, and stops costly plot-sale mistakes.