I noticed that WEST Marine has introduced a new definition for the acronym CHIRP, now suggesting that it stands for "Compressed High Intensity Radiated Pulse." This is another bad definition of chirp. The "R" just got changed to "radiated" from RADAR.
As I have previously noted, the pulse emitted by a chirp SONAR is not compressed and is not high-intensity. The emitted pulse is actually just the opposite: it is not compressed but is actually elongated, and it is not high-intensity but actually is lower-intensity than standard SONAR. The total energy of a chirp SONAR pulse can be high because the lower-intensity pulse has much longer duration that the usual very short SONAR ping.
It is amusing to see what advertising copywriters don't know about frequency-modulated pulse-compression SONAR methods. The irony of this latest WEST Marine invented acronym is its use as part of a presentation to "teach anglers" about chirp SONAR.
As I have said many times, the "chirp" refers to the audible characteristic of the linear frequency modulated pulse being emitted--it sounds like a bird chirp. The term chirp has been used to describe frequency modulated carrier signals for about 80-years, first applied to continuous wave Morse code transmission with carrier oscillators that were not particularly frequency stable. The only place you find these odd acronyms being used is in marketing literature for recreational SONARS aimed at anglers.
The "compression" occurs when the much longer transmitted signal is received and processed, not when it is sent. Using sophisticated signal processing methods, the longer time-domain and wider frequency-domain signal is effectively shortened in time by this method of processing. This is where the improvement in image resolution occurs--it is all in the receiver processing, not in the signal transmitting.
Also, resolution improvement is always related to the width of the frequency modulation. But we have buzz-words about "narrow band chirp" or "single frequency chirp." If a SONAR pulse is a single frequency, it cannot really be a chirp system. If a SONAR pulse is only frequency modulated over a narrow bandwidth, the gain in resolution from the pulse compression demodulation will be similarly limited.