The tracking cloud is an additional feature of DOUAR that can be used to calculate thermochron ages and estimate metamorphic grades for rocks.
### Setup
#### Activation and Saving
In the input file, set `ptracking = T`. The tracking cloud will be activated at timestep `tr_activation` (larger than nstep_spinup is recommended)
#### Injection Box
#### Reference
### Post-Processing
### Internals
The tracking cloud is a derived type that is activated at a user-specified timestep. The particles are injected in a box, either randomly or in a spaced grid and advected through the domain according to osolve velocities. Every n'th timestep, the position, temperature and (smoothed) pressure for these particles is written to a tracking output file (in separate subdirectory). If a particle hits the surface, its track extent is saved in a log array and the particle reinjected. If a particle exits through the side of the domain, the track is discarded and the particle reinjected. Reinjection happens in those elements that have the largest decrease in tracking particle density compared to the initial distribution.
In post-processing, either the entire path of all particles or only the surfaced tracks saved in the log array can be converted to vtk-files. Multiple output files regularly spaced in step number can be created at once. Input files can be regularly spaced as well. Usually only tracks that surfaced at the output timestep are written to the vtk file, but for an increase in density, surfaced tracks can be 'accumulated' over several timesteps.
Output variables for the tracks are: Speed, vertical speed, temperature, pressure, time, step number and particle/track ID. Variables and positions are written either in DOUAR units or natural units.
