Many thanks to all of you.
And here please let me tell you the background of this application first.
This TDOA application is a part of our rocket recovery system. Our little rocket is just like this:
The size of it is about 140cm*11cm(a cylinder). After the ignition it can finally reach the target about 5km away and our next plan will make it to 10/15km. We need a system to find it after the launch and the best result is that we can record flight trajectory. But for recovery system a tens of meters error is just ok for the moment. And we have a GPS(signal can be lost if the landing place is not perfect or the parachute failed) on it and Yagi antenna already in use. But we still want to have a better way to locate it. Furthermore if TDOA works, the heavy GPS module+ant can be removed. And a data transmitter will have two roles.
So the problem as ccsh mentioned, we may move the SDRs to another place as if we have 3 or more receivers when tracking the fixed target at first(okay, no rocket this time ). Just make it work will be enough at first. Even for this situation, move to another place will be ok.
Thanks for modimo I will read more about superresolution TDOA and others.
Oh, and does anyone have idea about roccket(but not a SpaceX Falcon like ) recovery system hahaha