To setup a cluser of capture devices (Raspberry Pi + SDR) across the city recording IQ values. Then have a public facing website radio-mapper.org that aggregates processed IQ data to give you a google map location of radio sources and filters.
Stefan Scholl presented this Experiments on Transmitter Localization with TDOA. You can see in the slide a link to async_rearrangements branch of librtlsdr. This is a good starting point for this project.
Radio Machine Learning Dataset Generation with GNU Radio
Time Difference of Arrival for Positioning
Signal Positioning using RTLSDR
Database of Signals
Detecting/Locating Unintended Radio Transmissions
Creating VHF heatmap with RTLSDR