Difference Between Radar and Sonar

RADAR and SONAR are both detection systems that can be used to identify objects and their position when they are not visible or at a distance. They are similar in that they both detect the reflection of a transmitted signal. This makes them easily confused with one another. They also both also serve as acronyms for a much longer description, with RADAR being short for Radio Detection and Ranging and SONAR for Sound Navigation and Ranging.[i] There are also additional differences between the two.

1. Type of signal used

The primary differences between radar and sonar is going to be the type of signal that they both use for detection. Radar detection relies on radio waves, which are part of the electromagnetic spectrum. Sonar uses sound waves, which are mechanical waves. Due to the different properties of both these wave types, they are both suited for different applications. The basic process of radar detection consists of sending a radio pulse into the air, of which some of that is reflected by objects. These reflections are captured by a receiver and speed of moving objects can be calculated using the Doppler Effect. The process of using sonar is similar by uses the sound waves instead. For this reason, sonar was used in the air prior to the use of radar.[ii]

2. Applications

The common held belief is that radar is used in the atmosphere and sonar is used underwater but this doesn’t accurately represent the variety of applications within the capacity of both systems. Since radar has a much larger range, it is used in many applications. These vary from air and ground traffic control, radar astronomy, air-defense systems antimissile systems, marine radar, aircraft anticollision systems, ocean surveillance systems, outer space surveillance, meteorology, altimetry and flight control, and guided missile target locating systems. There is also ground-penetrating radar that can be used for geological observations and range-controlled radar for public health surveillance.[iii] The military uses for sonar include: anti-submarine warfare, torpedoes, mines, mine countermeasures, submarine navigation, aircraft, underwater communications, ocean surveillance, underwater security hand-held sonar for divers, and intercept sonar. There are many other civilian uses for sonar too. These would include harvesting fish in fisheries, echo sounding, net location, remote operated vehicles, unmanned underwater vehicles, hydrooacoustics, water velocity measurement, bathymetric mapping, vehicle location and even for sensors that can assist the visually impaired.[iv]

3. Range and speed

Both radar and sonar rely on the speed of sound, cut since sonar is used in many underwater applications, that speed can be somewhat slower since sound waves travel more slowly in water than in the air. The speed can also be influenced by temperatures, salinity and pressure of the water. Active sonar is capable of detection of targets at a larger range, but it also allows the emitter to be detected at a far greater range too, which makes it unfit for many of its intended applications. Most uses of sonar use a type called passive sonar. It can have a greater range and is very stealthy and useful but the high-tech components are expensive.[v] Radar technology typically has a greater range than sonar, but it also can be influenced by a number of variables including the refractive index of the air (the radar horizon), height above ground, line of sight, pulse repetition frequency and the power of the return signal which can be affected by environmental conditions.[vi]

4. Development

There is another difference in how each technology developed and advanced. Sonar is found in nature and many animals have used it before humans developed an application. Bats and dolphins both use sonar in echo-location which allows them to communicate and “see” when they are otherwise unable. The technology was first used by humans when the first sonar device was developed to detect icebergs in 1906; it was further developed during World War I and military applications have driven its development since that time. Radio waves are also a natural occurring phenomenon as they are a part of the electromagnetic spectrum, but they have not been used by other animals. They were first explored in the 1880s by Heinrich Hertz and the technology was also explored by Nikola Tesla, who really had the vision that this could be used for detection. Pulse radar was developed in Britain and introduced to the United States in the 1920s. Advances for this technology have been made by both military and civilian interest.[vii]

5. Environmental concerns

The effects of sonar on marine animals has been studied and is shown to cause strandings of many marine mammals. These include the beaked whales who have a high sensitivity to active sonar. Blue whales and dolphins have also been affected. In addition to strandings, there are behavioral responses like disruption to feeding patterns. For the baleen whale, this disruption could have a large impact on the foraging ecology, individual fitness and population health. Sonar has also been shown to cause a temporary shift in the hearing of some types of fish.[viii] Unlike sonar, there are no naturally occurring and documented impacts to specific animal populations due to the use of radar. The WHO has studied the effects of these radio waves on cancer rates and have concluded that there is no evidence that radio frequency shortens human life spans or induces cancer. At very high levels of radio frequency there can be a reduced endurance, decreased mental acuity and an aversion to the field.[ix] Despite the indication that radio waves are generally safe, many individuals are still wary of too much exposure.

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