Two Way Ranging is a Time of Flight (TOF) method. With this method, positions will be calculated using trilateration. The time of the propagation of the signal is measured between the transmitter and the receiver. A signal is send from a tag to an anchor and back (hence the ‘two way’). It needs to be sent back because the clocks of the anchors and tags are not synchronized. This means that the timestamps taken at the tag are on a different timebase than those taken on the anchor.
With the 4 timestamps (2x transmission and 2x reception) we can accurately calculate how long the signal has traveled back and forth between the nodes. Dividing that time by two yields the TOF and thus the distance.
The airtime of the nodes is higher than for TDOA, so less positions can be calculated.

Time differences yield hyperbolas. The position of the tag is calculated by calculating the intersection of the hyperbolas. This technique is also called multilateration. Two anchors yield one TD (as opposed to only one anchor for one distance). This means a minimum of 3 anchors are necessary to calculate one 2D position and 4 anchors for a 3D position. The clocks of the nodes need to be synchronized. The better the synchronization, the higher the accuracy of the positions. Tags don’t need to be active very often so this method is power consumption friendly. We differentiate between 2 schemes (TDOA1 and TDOA2) based on where the time differences are measured.

Angle of Arrival is a method in which the direction of the propagation of the RF-signal is calculated on the receiving node, for example based on the phase difference measured on 2 different antennas. A 2D position can be derived from 2 angles with some simple triangulation.