
GPS – An Unconventional Tidal Gauge - sohkamyung
https://oceanbites.org/ben-watzak/
======
nmstoker
An interesting talk on this subject was given at PyConUK last year:
[https://youtu.be/AeScwg-nZk4](https://youtu.be/AeScwg-nZk4)

------
SamBam
Interesting. I would have naively thought that there were far more trivial
ways to measure water level directly (e.g. stand your sensor right over the
water and point a distance sensor straight down, or use a moveable floatation
device) but actually this indirect way can be done with a single GPS chip
(<$5), and remain entirely enclosed.

~~~
thatcherc
Can this Interferometric Reflectometry technique be done using just a cheap
GPS module? As I understand it you'd need to get access to something like the
raw IQ samples coming out of the GPS analog-to-digital converter in order to
determine the time difference between the true signal and the reflected one,
which I wouldn't expect to be possible with a cheap integrated GPS - I'd love
to hear it's possible though!

~~~
jhayward
From a quick look at

[https://link.springer.com/article/10.1007/s10291-018-0744-8](https://link.springer.com/article/10.1007/s10291-018-0744-8)

 _" At some level, all GNSS-IR studies are based on the analysis of SNR
patterns created by the interference of direct and reflected (or multipath)
GNSS signals."_

It appears they are using the effect that reflected signal has on the
receiver's reported SNR value to impute multipath frequencies.

