An interesting article, of special interest on TDoA (Time difference of Arrival), a direction finding technique.
A few weeks ago we posted about some experimental work going on with Time Difference of Arrival (TDoA) direction finding techniques on KiwiSDR units. The idea is that public KiwiSDRs distributed around the world can be used to pinpoint the physical locations of any 0 - 30 MHz transmitter using the TDoA technique. This feature has recently been activated and can be accessed for free via any KiwiSDR.
The KiwiSDR is a US$299 HF SDR that can monitor the entire 0 - 30 MHz band at once. It is designed to be web-based and shared, meaning that the KiwiSDR owner, or anyone that they've given access, can tune and listen to it via a web browser over the internet. Many public KiwiSDRs can be found and browsed from the list at sdr.hu or by signal strength and location on this website.
Additinal story at: https://www.rtl-sdr.com/kiwisdr-tdoa-direction-finding-now-freely-available-for-public-use/