It is the wish of experimental fluid dynamicists is to be able to measure complex, three-dimensional turbulent flow fields globally with very high spatial and temporal resolution. Towards this goal, several volumetric velocimetry methods have been developed that are worth noting for allowing for 3D measurements: defocusing PIV, holographic PIV, tomographic PIV, synthetic aperture PIV, and plenoptics PIV. In this presentation, we introduce a volumetric PTV methodology that can be used for either a single camera or multi-camera system. The single camera hardware setup is based upon that developed by Willert & Gharib. Here we are able to identify larger number of particles by color-coding the pinholes in order to separate particle exposures from different pinholes, though this step is clearly not needed for the multi-camera system, as each camera images obtains separate exposures of the particle field. In addition, an algorithm is developed that can identify overlapped particles, thereby allowing for identification of larger number of particles. A calibration-based triangulation method is used to identify triplets. A vision-based algorithm is developed to pair particles. Finally, a PTV outlier detection method is developed based on the universal PIV outlier detection method by Westerweel and Scarano. These developed algorithms, though developed for the DDPIV setup, can easily be used for other multi-camera configurations. To test the ability of our methodology, we implemented this methodology to a micro-scale 3D-PTV system, and used it to image flow behind a micro-scale backward-facing step, and within a micro-channel flow. In addition, we also implemented this methodology to a macro-scale 3D-PTV system and used it to image flow behind a backward-facing step. Details of our work can be found in Tien et al., Grothe et al., Duncan et al., Lei et al., and Tien and Dabiri.