Airborne Profiling

Applications for airborne UWB radars fall into two technology categories, - those using UWB images (UWB Synthetic Aperture Radar) and those using profiles. The imaging (SAR) applications use the UWB radar's ability to cover large areas per flight hour, (typically 200-400 sq. km /hour). However, the depth of penetration is currently limited by surface clutter which competes with the subsurface image rather like a double exposed photograph. In the case of airborne profiling however, the beam is pointed directly below the aircraft, and the resultant data looks very much like ground-based GPR except that the spot size is larger. In this case, the radar is limited by absorption, and can achieve penetration down to 10m or more depending on soil conductivity. The airborne method was first developed for ice and snow measurementsand was used to great effect in measuring ice thickness on the great Lakes in an effort to extend the Seaway shipping season. Dr. Vickers received an Industrial Research, IR-100 award in recognition of this work. Later, while Dr Vickers was at SRI International, the method was adapted to forest penetration in a program for the World Bank to map ground characteristics beneath tropical forest canopy. With the radar being flown in closely spaced parallel survey lines, the data could be assembled in a computer to give a Digital Elevation Modal (DEM) of the landform despite the surface being completely invisible, as shown below.

The technology can be used for

  • Search for shallow tunnels (less than 30ft)
  • Cavity and bunker detection
  • Profiling through trees
  • Route selection in forest regions
  • Site selection planning for construction and pipeline projects
  • The flight envelope for imaging GPR is typically 6,000-10,000ft AGL and 150 kts groundspeed. With the evolution of fast data handling computers, higher flight speeds could be made possible. The radar equipment weighs approximately 450 pounds and requires 2 KW of electrical power. The equipment has been flown in turboprop aircraft such as the Beech Kingair -200 and the BAC Jetstream-31. It has also been flown in older reciprocating engined aircraft (Beech Queenair). The aircraft modifications can be minimal, since most of the external equipment can be housed in a baggage pod as shown in the figure below. The staff of IRC have designed and managed the construction and flight test of a number of such systems, which were used with success in mapping minefields, detecting illicit activity beneath forest cover, and other military applications.
    There are few such systems in the world at this time. The UK operates a very high resolution, named MINESEEKER, (10cm) system developed by the Government and mounted on an airship. In the US, the government operates one system with medium resolution (1m) built by SRI International, and a similar system built by Loral, both flying on a C-54 aircraft. . The Swedish government flies a very low resolution system (2.5m), named CARABAS. There are no other systems currently available for operational use, nor are there any systems at present that can be flown on fast moving aircraft.

    Radar Profiling Aircraft