njkayaker

It doesn’t distinguish “that one vehicle” at all.

njkayaker

It can’t do this, obviously. (No one has made the claim it could.) So, that can’t be its purpose.

It’s more of a “don’t mosey left” warning device. You get a longer off awareness than a mirror provides. And it might be useful for people who can’t hear cars. It might be more useful when there are fewer cars.

This is just strange. People who use (and like) them are “repetitively diving for shoulders. You have no idea how these are used.

If people have an issue with this, they can turn off the alarms. It’s not the dire situation you make it out as.

After trying one for a while, I find it doesn’t do much for me. Lots of people like them a lot. It’s nice they have the option even if you “not interested”.

njkayaker

This is not true.

There are “presence detectors” that use “mmWave” and track
multiple moving objects with no moving parts or cameras.

FBinNY 

You're taking this too literally, and distorting it by removing the context provided by the preceding sentence. My point was that the unit wouldn't provide any actionable information (for me), since it can't distinguish between cars that are a danger to me from those that aren't.

But you are right that I have no idea how these are used by others. However, that's not something I need to care about.

Nor does the fact that I've no interest in using it, imply any judgement about other people's choices. I don't do, nor judge, what lots of people do, and do what lots of people don't, and it works out fine.

tomato coupe

They do provide useful actionable information -- just not that particular piece of information. So, yes, if that's all you care about it's clearly not for you.

Troul 

Depending on how you view it, the traffic alert will change the color of the screen section based on vehicle proximity.
red is potential dedz
yellow, stay mellow

njkayaker

Your “actionable” was “diving into the shoulder” That’s deranged. The context doesn’t help you. No one does that.

I’m not sure if co

The not understanding how people use them, the whole “to many alarms”, the “too much reliance on technology” (paraphrased), and the “diving onto the shoulder” nonsense all add up as kind of “judgy” and disapproving.

Steve B.

I think we are missing the point of the very basic function, with an assumption that ALL cars coming up behind you are a danger to you potentially and that the radar at minimum warns you that there’s a vehicle approaching. You want to know if one of those vehicles has a driver who is not paying attention and will hit you. Nothing can do that. All a radar unit can do is warn you of an approaching vehicle. Some folks use mirrors for this, I use a mirror but am on occasion not watching and miss that a car is behind me. What I desire of the radar is to fill in for when I miss what is visible in the mirror.

FBinNY 

I'm not going to argue. I posted why I wasn't interested in acquiring this bit of tech, and am happy to let people decide for themselves.

tomato coupe

I think people would be more receptive to your opinion if your lack of interest wasn't based on an unrealistic expectation.

SoSmellyAir

Does the Trek CarBack have an mm wave radar? I did not know that those are already on the market. The mm wave presence detectors seem to be designed for interior space?

How does an mm Wave radar / presence detector distinguish between: (1) an object that has shifted its lateral position; (2) an object that has slightly changed its speed; (3) multiple objects, side-by-side, closing at slightly different speeds?

PromptCritical 

The Trek CarBack operates at a much higher frequency than the Varia, so it “should” be more accurate, but GP Lama reports it isn’t.

Answers to questions

1. Would require more than one emitter or an array.

2. Change in the Doppler shift in the radar return.

3. Different return for each object with a different Doppler shift for each.

Cheers, Mike

FBinNY 

There's no expectation, either realistic or not, here. Simply a statement that, for me, the info it offers isn't enough to cross the line from pass to buy.

SoSmellyAir

Looking into this further, it seems that the ability to detect lateral position would require at least two emitters transmitting at different frequencies that are sufficiently far apart that they would not overlap even with Doppler shifts, right?

PromptCritical 

That would be one way to do it. The other is with a pulsed array. No idea which is cheaper, I doubt either would be affordable for consumers. Likely use a lot of power too.

SoSmellyAir

Yeah, which brings me back to my original question: how does the Trek CarBack do it? It has an MSRP of $200, same as the Garmin Varia RTL-515 that many of us use.

howaboutme

If you see the initial reviews, it doesn't do it (well).

SoSmellyAir

Yes, I see that. I am more asking / wondering about how Trek implements this feature and tests the implementation to determine / justify saying that it can detect the lateral position of an approaching vehicle.

njkayaker

It might (not sure).

I only know of the interior sensors. I'm not sure why they couldn't be used outside.

Black magic, I think. Actually, it looks like they have two antennas that are separated a bit. The mmwave sensors can detect breathing. It would seem it should have no problems detecting slightly different or changing speeds. The indoor sensors can track a limited number of objects (like 3).

njkayaker

Why would anybody care?

Your "whys" were kind of dismissive too.

So, it's something you don't know much about and don't care to learn anything about. Is telling people you are "not interested" in it at all useful to them? (Hint: no, it's not useful at all.)

PromptCritical 

"mm wave radar" refers to the wavelength of the radar. The smaller the wavelength (higher frequency) the more accurate the radar can be. Indoor mm wave radar devices (intrusion sensors) are cost effective because they are aimed at the mass market which drives the cost down due to high production volumes and competition between providers. The total number of bike radars sold will be a minuscule fraction of the indoor sensors sold.

njkayaker

Why can't the bike radars use the same (or similar) sensors that are "cost effective"?

They aren't really "intrusion detectors". They are more than just that. They can track objects within a space. They can detect motion as subtle as breathing.

FBinNY 

About as useful as your unprovoked attacks. However, it's a forum and we each post reflective of our worldviews.

Some say what they think, others prefer to attack what people think. So, you be you and I'll be me.

njkayaker

Again, people can comment about your comments. Even criticize them. You shouldn't say misleading things (the "dive into the shoulder" nonsense) and expect to immune comments about that.

Why have this in your sig?

FBinNY 

Absolutely. Feel free to continue being who you are. May you future be filled with people of similar mindset.