The way of getting the altitude of xmax is not accurate, and its dangerous.

[mjtueros]

grand/lib/python/grand/radio/modules.py

Line 153 in 1567c06

def _dist_decay_Xmax(zen_inj, injh, xmax):

Getting the position of xmax using a function with hard-wired numbers is not optimal at all. We will be simulating with different atmospheric profiles eventually.

More importantly, the numbers used here dont correspond to the actual atmosphere that is usually used in ZHAireS simulations (the Linsley standard atmosphere, a multilayer atmospheric model).

Doing the integral from the top of the atmosphere, where the atmosphere is very thin, is also not ideal, since this is where the atmospheric models have the greatest relative diferences....and this will translate to bigger errors in position (since smaller densities require larger distances to make the same mass path)

I belive the position of xmax is an important parameter, that should be part of the event structure and should be provided by the shower simulator, either as an output of the simulation or as a responsibility of the routine that reads the simulation output to build the event (that can try to calculate it from the information available from the simulation, or the simulation input file, or if it is not available make any desired aproximation).

By the way, ZHAireS already outputs the exact position of Xmax (and it will be correct regardless of the atmospheric model used during the simulation).

Cheers!
Matias