Some echolocation signal parameters can be studied using a single receiver. However, studying parameters such as source level, directionality, and direction of signal emission require the use of multi-receiver arrays. Acoustic localization allows for determination of the position of echolocators at the time of signal emission, and when multiple animals are present, calls can be assigned to individuals based on their location. This combination makes large multi-receiver arrays a powerful tool. Here we present an overview of different array configurations used to study both toothed whales and bats, using a suite of systems ranging from semi-3D-minimum receiver number-number-arrays (3D-MINNAs), linear-2-D-over determined arrays (2D-ODAs), to 3-D-over-determined-arrays (3D-ODAs). We discuss approaches to process and summarize the usually large amounts of data. In some studies, the absolute position of an echolocator and not only relative to the array is crucial. Combining acoustic localizations from a source ...