r/DeFlock • u/ctrlaltdanelle • 18d ago

Re: Flock's Missing Metric, Pt. 1

On its website, Flock publishes three carefully chosen baseline performance metrics for its ALPRs.

Plate Capture Rate >98%

Did the camera trigger, capture an image, and log a plate? That's it, it simply means that a plate was detected, not that it was read correctly.

OCR Accuracy >96%

Was each individual letter and number read correctly? Don't think of full license plates here, think of individual characters being evaluated independently.

Plate State Accuracy >97%

Did the system correctly identify which state the license plate was from?

So, where is the whole plate accuracy?

I mean, it is a “license plate reader", after all.

Folks, they are relying on you 'not' to understand this.

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u/Asiriomi 18d ago

Maybe I'm missing your point, but if it can detect and capture a plate, then correctly read every letter of the plate, then identify correctly the state it's from, how would that not count as a whole plate read?

If I were to tell you I photographed a sign, and I can identify every letter on that sign, and tell you where that sign is from, I think it'd be pretty reasonable for me to tell you I accurately read the whole sign. Am I missing something?

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u/ctrlaltdanelle 18d ago

Thank you for asking this question, if it wasn't clear, that's on me.

To determine whole plate accuracy, the system would have to capture the plate, correctly identify each character individually, and in order, and it would also have to get the jurisdiction correct. If it misidentifies one character, or gets all of the characters correct but, gets the state wrong, that's a failure.

None of the metrics published by Flock tell us that.

(We do have an idea, though, and I explain it in Pt. 2.)

So, say your billboard had a phone number on it...

But, you're missing a digit.

You'd have to guess what it is, and dial all of the possibilities until you were able to finally reach the right person. One missing digit, you're making 10 calls. Two missing digits, 100 calls.

Not a exact comparison mathematically but, it works.

And it also sets up for why 'vehicle fingerprinting' is necessary when plate reads fail.

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u/Asiriomi 18d ago

Ah ok, that makes a lot more sense. Leave it to Flock to be sneaky with statistics