Gyroscope: I'd have thought that it was worth working on the gyroscope data to see if you can us its known location in the car + car known geometrical performance when turning + what the accelerometers say to interpret the gyro result more appropriately. A "perfect" gyro should give you better results than "perfect" accelerometers. Reality and Murphy will make this less so, but it's still a shame to abandon the gyros.
Magnetometers - aka compass: You'll have problems if you install a compass where it is affected by large items of ferromagnetic material.
Under a car dashboard certainly qualifies as a really bad location.
You can carry out a very low cost test by taking any compass and holding it in various positions under the dashboard (still in sight) and seeing how it changes, Then turn the car 90 degrees and repeat.
Where it matters "real people" perform "compass swinging" to either produce a deviation chart or to make adjustments by the use of either small magnets or pieces of ferromagnetic (usually) metal. (eg Brass is very slightly diamagnetic (~= "anti ferromagnetic") and will also affect the field but much less and oppositely in sense.
If you make a deviation table then it could be adjusted for in software.
Useful compass deviation page.
They say:
In most cases, these difficulties can be overcome by 'adjusting' the compass. This is the process of placing small magnets around the compass site or of altering the positions of adjustment magnets within the compass body. Traditionally, it has always been considered a task for specialist compass adjusters and beyond the means of the average boat owner.
This is no longer true. With C-Swing, preparing a deviation chart is now simply a question of selecting a suitable shoreside object, entering its true bearing from the chart, then entering its compass bearing as the boat is sailed on a range of headings. With the built-in maths package, headings do not need to be exactly on compass points and, if suitably spaced, as few as 5 are sufficient to prepare a full chart showing deviations at 10� intervals. Furthermore, C-Swing also computes a set of magnetic coefficients and gives guidance on placing corrector magnets and making adjustments.
That sounds hard, and it's not utterly trivial, but a bit of thought about what you are trying to correct for and how external magnets help will show that it's a fairly straight forward process. And, it's likely that intelligence-informed trial and error will allow you to do an OK job.
Here are people who do it do it for a living
According to the above page, here are people who didn't do it properly - USS Port Royal grounding in 2009. However, according to Wikipdia report it was not a compass error but a more high tech navigation system error followed by lots of human error that lead to the grounding. I'll leave the picture as it does make the point of what can happen if your navigation system is faulty. Just stay away from coral reefs with your car! :-). (Reef cost them $15M to repair. Ship between $25M & $40M)
Useful page here
Wikipedia - historical - interesting
They say:
- Diagram of a 19th century binnacle housing a compass. It has two soft iron spheres (Q) to correct for induced magnetization.
I'm not a radar expert by any means, but I think I understand the general concepts well enough to try to answer your questions.
What specific requirements on the peak and average powers and the widths of radar pulses was chirped-radar designed to overcome? Were these purely 'internal' concerns regarding the electronics, or were there external goals and restrictions that were hard to meet otherwise?
The basic problem in radar is to get both adequate power for total range and good timing resolution for range resolution. It is hard to build high-power amplifiers for microwave frequencies. You want to have a lot of energy in each transmitted pulse, but you also want to keep the pulse short. The solution, as you have found in optics, is to stretch the pulse by chirping it, which allows the power amplifier to operate at a lower power for a longer time in order to get the same pulse energy.
Now, in radar, it doesn't matter if you don't compress the pulse again before feeding it to the antenna — the chirped pulse works just as well as the compressed pulse in terms of detecting objects.
In fact, you gain additional advantages when the reflections come back, because now you can amplify the chirped signal in the receiver (getting some of the same advantages as in the transmitter amplifier regarding peak-to-average power), and you can use a "matched filter" to compress the pulse just prior to detection, which has the additional advantage of rejecting a lot of potential interference sources as well. The narrow pulses coming out of the receiver filter give you the time resolution you need.
Is the name 'chirped pulse amplification' ever used in a radar context?
Generally not, because amplification isn't the only reason that chirping is used.
Is the optics-style CPA - stretch, amplify, compress, and then use the pulse - used at all in radar applications, or in broader electronics fields?
Not to my knowledge, but it would certainly be feasible.
Best Answer
You'd be surprised.
This is actually topic of ongoing research, and of several PhD dissertations.
The question which radar waveforms and algorithms can be used to mitigate interference is a long-fought over one; in essence, however, this breaks down to the same problem that any ad-hoc communication system has.
Different systems solve that differently; you can do coded radars, where you basically do the same as in CDMA systems and divide your spectrum by giving each car a collision-free code sequence. The trick is coordinating these codes, but an observation phase and collision detection might be sufficient here.
More likely to succeed is collision detection and avoidance in time: simply observe the spectrum for radar bursts of your neighbors, and (assuming some regularity), extrapolate when they won't be transmitting. Use that time.
Notice that wifi solves this problem inherently, much like described above, in a temporal fashion. In fact, you can double-use your Wifi packets as radar signals and do a radar estimation on their reflection. And since automotive radar (802.11p) is a thing, and the data you'd send is known to you and also unique, you could benefit from the orthogonal correlation properties of a coded radar and the higher spectral density and thus increased estimate quality of time-exclusive transmission.
There's a dissertation which IMHO aged well on that, and it's Martin Braun: OFDM Radar Algorithms in Mobile Communication Networks, 2014.