ADSBExchange is an aircraft tracking website service which aggregates ADS-B data from contributors running RTL-SDR's or similar receivers worldwide.
However, unlike other flight tracking sites such as flightaware and flightradar24, ADSBExchange sets themselves apart by proudly refusing to censor the tracking of military and private jets that have requested privacy. One area where this refusal to self-censor helps is with the "Dictator Alert" service. This is a service that automatically tracks the movements of private aircraft owned by authoritarian regimes via the ADS-B data collected and shared by ADSBExchange.
Recently ADSBExchange upgraded their web interface moving from the old Virtual Radar Server system to tar1090 which is a more fully featured open source display for dump1090. This new interface has some great features, like the ability to view the complete flight track history of any aircraft on a particular day, the ability to display only military aircraft and the ability to filter by altitude and aircraft type.
For ADS-B decoding, dump1090 is an RTL-SDR compatible program that is commonly used. In order to provide information about the aircraft being detected (e.g. icao24 hex address, registration/tail number and sometimes the type of aircraft like A380), dump1090 uses an offline database. Unfortunately this database has not been maintained in a very long time, so it is now out of date, and so cannot display information about many aircraft.
Contained within the data is the icao24 hex address and registration/tail number. By collecting this VDL2 data over a number of days, a new database can be generated which can then be imported into the dump1090 database. It however, doesn't seem to acquire aircraft type data.
SonicGoose writes that the reason that many PlanePlotter users are moving away from the simpler GUI based RTL1090 ADS-B decoder is because dump1090 provides better raw data to use for multilateration. Multilateration is a technique supported by PlanePlotter which used data shared from multiple receivers to determine the location of an aircraft, even if that aircraft is not transmitting location information.
Dump1090 is a popular command line ADS-B decoder which many people believe has superior decoding performance compared to other decoding software. Previously it has only been available for Linux and Mac operating systems, however recently it has been updated with a Windows command line version. The most up to date branch of dump1090 can be downloaded from GitHub here.
To install dump1090 on Windows follow these steps:
Download the dump1090 zip file from the GitHub download link.
Copy the libusb-1.0.dll, rtlsdr.dll and pthreadVC2-w32.dll files from the official RTL-SDR Windows release zip file to the dump1090 folder. Rename pthreadVC2-w32.dll to pthreadVC2.dll.
Double click on dump1090.bat.
The batch file starts a dump1090 webserver which can be viewed in any browser by going to http://localhost:8080. You may wish to edit the batch file and add extra flags such as –aggressive and/or –fix to improve decoding.
YouTube user 907h9879070g9790 has posted a video showing Virtual Radar Server running on a Raspberry Pi with the Raspian hardfloat image OS installed. He used Mono to allow the .NET based Virtual Radar Server to run on the Raspberry Pi. Instructions for using Virtual Radar Server with Mono can be found here.
Combined with an rtl-sdr and dump1090, ADS-B packets can be sent to Virtual Radar Server, and then the aircraft radar map can be viewed on a PC or internet enabled device via a network connection. This can allow a small self contained remote ADS-B monitoring system to be set up.
EDIT: Unfortunately the video owner has taken down the video.
The RTL-SDR can be used as a super cheap real time air radar. Modern planes use something called an ADS-B (Automatic Dependent Surveillance-Broadcast) Mode-S transponder, which periodically broadcasts location and altitude information to air traffic controllers. The RTL-SDR can be used to listen to these ADS-B signals, which can then be used to create your very own home aircraft radar system. Compared to dedicatedcommercialADS-Breceivers which can go for between $200 - $1000, the $20 RTL-SDR is very attractive for the hobbyist in terms of price. However, note that the RTL-SDR probably shouldn't be used for ADS-B navigation in a real aircraft for safety reasons.
ADS-B broadcasts at a frequency of 1090 MHz. It has been discovered by the RTL-SDR community, that the RTL-SDR with R820T tuner has the best sensitivity at this frequency. The E4000 and other tuners perform poorly in comparison. So it is recommended that you obtain an R820T tuner if you want to set up ADS-B decoding with the RTL-SDR. Recently there has also been talk about the R820T2 tuner, which seems to have slightly better performance too. See the Buy RTL-SDR dongles page for more information on where to purchase.
We also now note that recently new higher end SDR's like the $199 Airspy have developed very good ADS-B receivers that are several times more sensitive that the RTL-SDR.
Examples of RTL-SDR used as an ADS-B air radar
In this video, YouTube user Superphish shows a timelapse of air traffic over New Zealand using RTL-SDR, ADSB# and Virtual Radar Server.
ADSB Virtual Air RADAR with RTL SDR (RTL2832), ADSB Sharp and Virtual Radar Server