The use of decibels (dB) is incredibly common for all sorts of sensor work, whether with radars, sonars or measuring people's hearing (the use that the average person is most familiar with); because it's a convenient way of writing really long numbers in only two digits with reasonable accuracy.

For example, if you are trying to express the RCS of an insect, it would be inconvenient to try and remember 0.00001 m2; but if you convert it to decibels, you can just say "-50 dBsm".

Measurement systems in use in the sensor community are:

• dBsm: Used for Radar Cross Section (RCS) measurements. Base unit is the square meter.
• dBw: Used for Radar and Sonar power level measurements. Base unit is the watt.

It's important to remember the base unit used for that measurement. If you were trying to convert a 5 megawatt peak power radar into dBw, you'd first have to convert the power level from 5 megawatts to 5,000,000 watts before you converted it into log10 form.

Computing Decibels (dB) from Signal Level

dB = 10 * log₁₀(U)

Where:

dB: Decibel Level
U: Signal Level

Obtaining Original Signal Level from Decibels

U = 10^{(dB / 10)}

Where:

U: Signal Level (Original Units)
dB: Decibel Level