Radar is now redundant ?

[goboatingnow]

Originally Posted by Bycrick

Minor corrections.
"Radar uses Doppler shift to determine distance to objects"
No it doesn’t. Pulse radars measure the time required for the pulse to be reflected. Doppler shift has nothing to do with it. CW radars use a variable frequency transmitter. Measuring the difference between the sent and received frequency gives a measure of distance.

Interpreting Doppler shift can give an indication whether the target range is closing or opening.

There might be military radars that can yield information on shape and size, but I doubt any small boat radar will.

All modern boat radars are now available with CHIRP and Doppler.

[Statistical]

Originally Posted by goboatingnow

All modern boat radars are now available with CHIRP and Doppler.

The thing he was saying is doppler isn't needed to give you the distance. That is easily done via time of flight. The speed of light in air is a (near) constant. So distance can be easily measured.

Doppler gives you information on if the object is moving towards or away from you. It could also give you velocity although I don't know of any consumer radar that does that.

[Bycrick]

Statistical— Thanks for the support. What I was saying is that any Doppler effect tells you absolutely nothing about the range to the target. It tells you how fast the sender and receiver are moving relative to each other. CHIRP, properly known as FMCW, radar determines time-of-flight by comparing the current frequency being transmitted with the frequency of the returned signal. Since the frequency is being changed at a constant rate, the difference in frequency is directly dependent on how long it took to return.

[Kelkara]

Originally Posted by Bycrick

Statistical— Thanks for the support. What I was saying is that any Doppler effect tells you absolutely nothing about the range to the target. It tells you how fast the sender and receiver are moving relative to each other. CHIRP, properly known as FMCW, radar determines time-of-flight by comparing the current frequency being transmitted with the frequency of the returned signal. Since the frequency is being changed at a constant rate, the difference in frequency is directly dependent on how long it took to return.

I have a simple technical question ... if CHIRP measures a change in frequency to calculate distance, and the doppler effect measures a change in frequency to calculate movement ... how is it possible to combine both in the same unit?

[donradcliffe]

Originally Posted by Statistical

The thing he was saying is doppler isn't needed to give you the distance. That is easily done via time of flight. The speed of light in air is a (near) constant. So distance can be easily measured.

Doppler gives you information on if the object is moving towards or away from you. It could also give you velocity although I don't know of any consumer radar that does that.

Your response is appropriate for the old pulse radars, but not for the new broadband radars. The old radar calculated distance based on time of flight of a high power pulse.

The broadband radars transmit a continuous wave and vary the frequency with time. They calculate distance based on the difference in frequency between the transmitted and reflected signals.

For a layman's description of what is currently available, see

https://www.westmarine.com/WestAdvis...g-Marine-Radar

[goboatingnow]

Originally Posted by Kelkara

I have a simple technical question ... if CHIRP measures a change in frequency to calculate distance, and the doppler effect measures a change in frequency to calculate movement ... how is it possible to combine both in the same unit?

CHIRP radar facilitates Doppler detection and calculation ,

[Bycrick]

Kelkara's question is one I avoided because I didn’t know the answer. But CHIRP certainly works when the little or no relative change in distance between the sender and receiver. Otherwise CHIRP depth sounders wouldn’t work.

The statement "all modern radars boat radars are available with CHIRP” is also wrong. Vendors are still selling new pulse radars. There are advantages and disadvantages to each type.

[Cadence]

Radar may go the way of RDF and loran but not in the near future.

[Statistical]

Originally Posted by donradcliffe

Your response is appropriate for the old pulse radars, but not for the new broadband radars. The old radar calculated distance based on time of flight of a high power pulse.

The broadband radars transmit a continuous wave and vary the frequency with time. They calculate distance based on the difference in frequency between the transmitted and reflected signals.

For a layman's description of what is currently available, see

https://www.westmarine.com/WestAdvis...g-Marine-Radar

Agreed it was a simplification. The key thing is that broadband radars also don't rely on doppler to determine range. Doppler is for determining stuff other than range.

For the kind of radar available to most cruisers largely tell you if the object is moving towards or away from you. More advanced doppler analysis can tell you a lot more like the velocity of the object and combined with other data the heading and track.

[goboatingnow]

Originally Posted by Cadence

Radar may go the way of RDF and loran but not in the near future.

Don’t think radar will ever get supplanted , modern autonomous cars have made huge advances in radar FMCW ( CHIRP) and Doppler processing. Add in more DiGital signal processing eg and radar has some time to run.

What’s we’ll see is more yacht integration, with radar drawing ,ais etc all contributing situational awareness info to yacht crews.

[Cadence]

Originally Posted by goboatingnow

Don’t think radar will ever get supplanted , modern autonomous cars have made huge advances in radar FMCW ( CHIRP) and Doppler processing. Add in more DiGital signal processing eg and radar has some time to run.

What’s we’ll see is more yacht integration, with radar drawing ,ais etc all contributing situational awareness info to yacht crews.

I was referring to radar as we know it. When we go the autonomous boats can we call it sailing/cruising? Doubt I'll ever see it, nor would I want to.

[Scorpius]

Originally Posted by Cadence

I was referring to radar as we know it. When we go the autonomous boats can we call it sailing/cruising? Doubt I'll ever see it, nor would I want to.

Ah yes. I too yearn for the old horse and buggy days!☺

[Cadence]

Originally Posted by Scorpius

Ah yes. I too yearn for the old horse and buggy days!☺

I can't imagine what is going to happen when the electrics take a dump on someone, although I think that is here today. I'm old and crochety but hope the people reliant on their electronic know how to get home.
The horse and buggy days were exhilarating.

[goboatingnow]

Originally Posted by Cadence

I was referring to radar as we know it. When we go the autonomous boats can we call it sailing/cruising? Doubt I'll ever see it, nor would I want to.

I was talking about future advances in radar will be driven by technology in autonomous cars. That technology will also aid us.

[goboatingnow]

Originally Posted by Cadence

I can't imagine what is going to happen when the electrics take a dump on someone, although I think that is here today. I'm old and crochety but hope the people reliant on their electronic know how to get home.

The horse and buggy days were exhilarating.

We do know cause we understand it !

Ps also can use a sextant