Triangulate after just do the linear. Try to put the receiver as close in line with the rocket path.
Triangulate for real will need spread-out receivers and maths that will require fast high precision floating point more suited to a PC. The programming would be pretty heavy with changing rates in 3D.
Just the linear case to approximate position will take more than it first seems and won't tell about side motion. But the doppler of acceleration will be simple. Make the pulses at high note audible frequency and hook up a speaker to the receiver output, you will hear the doppler shift.