A method for measuring a fluid flow, the method comprising - providing a plurality of transceivers (10a-10f) disposed at predetermined locations distributed along a perimeter around the fluid flow and using the transceivers (10a-10f) to transmit and receive acoustic signals (Sda,Sad,Saf,Sfa) through the fluid flow there between; wherein the transceivers (10a-10f) comprise a plurality of transceiver pairs (10a,10d; 10a,10f); wherein a respective transceiver pair (10a,10d) forms a respective acoustic path (Lad) through the fluid flow there between; wherein a plurality of different acoustic paths (Lad,Laf) through the fluid flow is formed between different transceiver pairs (10a,10d; 10,10f); - measuring different time intervals (Tad,Tda,Taf,Tfa) between respective times of transmitting and receiving the acoustic signals (Sad,Sda,Saf,Sfa) along the plurality of different acoustic paths (Lad,Laf); - calculating a velocity map of the fluid flow by using the measured different time intervals (Tad,Tda,Taf,Tfa) with a model of the fluid flow, wherein the model of the fluid flow defines the velocity map with different flow velocities (V1,V2,V3) in a cross-section plane transverse to the fluid flow; wherein the velocity map is mapped onto respective lengths of each of the plurality of different acoustic paths (Lad,Laf) to determine the different flow velocities (V1,V2,V3) along said lengths of the different acoustic paths (Lad,Laf) in accordance with the velocity map; wherein the flow velocities (V1,V2,V3) along the lengths of the respective acoustic paths (Lad,Laf) are used to calculate modeled different time intervals between the respective times of transmitting and receiving the acoustic signals along the plurality of acoustic paths; wherein the modeled different time intervals are fitted to the measured different time intervals (Tad,Tda,Taf,Tfa) in accordance with the velocity map. - providing a plurality of transceivers (10a-10f) disposed at predetermined locations distributed along a perimeter around the fluid flow and using the transceivers (10a-10f) to transmit and receive acoustic signals (Sda,Sad,Saf,Sfa) through the fluid flow there between; wherein the transceivers (10a-10f) comprise a plurality of transceiver pairs (10a,10d; 10a,10f); wherein a respective transceiver pair (10a,10d) forms a respective acoustic path (Lad) through the fluid flow there between; wherein a plurality of different acoustic paths (Lad,Laf) through the fluid flow is formed between different transceiver pairs (10a,10d; 10,10f); - measuring different time intervals (Tad,Tda,Taf,Tfa) between respective times of transmitting and receiving the acoustic signals (Sad,Sda,Saf,Sfa) along the plurality of different acoustic paths (Lad,Laf); - calculating a velocity map of the fluid flow by using the measured different time intervals (Tad,Tda,Taf,Tfa) with a model of the fluid flow, wherein the model of the fluid flow defines the velocity map with different flow velocities (V1,V2,V3) in a cross-section plane transverse to the fluid flow; wherein the velocity map is mapped onto respective lengths of each of the plurality of different acoustic paths (Lad,Laf) to determine the different flow velocities (V1,V2,V3) along said lengths of the different acoustic paths (Lad,Laf) in accordance with the velocity map; wherein the flow velocities (V1,V2,V3) along the lengths of the respective acoustic paths (Lad,Laf) are used to calculate modeled different time intervals between the respective times of transmitting and receiving the acoustic signals along the plurality of acoustic paths; wherein the modeled different time intervals are fitted to the measured different time intervals (Tad,Tda,Taf,Tfa) in accordance with the velocity map.