5 ms·
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
by SamBam 7y ago
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 7y agoCan 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 7y agoFrom 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.