## Programs to Compute ROT and ROTI

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The two programs are MATLAB functions to compute 30-seconds Rate of change of TEC (ROT) and 5-minute ROT Index (ROTI) from TEC data

Updated 9 May 2023

The two programs are MATLAB functions to compute 30-seconds Rate of change of TEC (Total Electron Content) (ROT) and 5-minute ROT Index (ROTI) from TEC data, usually obtained from GPS/GNSS receivers or other instrument.
The function named 'rot30s_mean' is first used to generate the 30-seconds ROT, and then if desired, the function named 'roti5m' is used to generate the 5-minute ROTI.
%----------------------------------------------------------------------------
The syntax for rot30s is:
[nsecs_out, prn_out, el_out, lon_out, lat_out, rot30s]=rot30s_mean(nsecs, prn, el, lon, lat, el_mask, tec)
The inputs (described below) are column vectors, except for el_mask which is a scalar:
nsecs: number of seconds from midnight (can be UT or LT)
prn: satellite identifier (can be strings/characters/numeric/numbers)
el: satelite elevation angle (degrees)
lon: longitude of IPP (degrees)
lat: latitude of IPP (degrees)
tec: TEC (TECU)
The outputs (described below) are also column vectors:
nsecs_out: output number of seconds from midnight (can be UT or LT, same unit as input nsecs) at resolution of 30s
prn_out: output satellite identifier (strings)
el_out: output satelite elevation angle (degrees) computed at 30s resolution, as the midpoint of satelite elevation angles over which roti5m is computed
lon_out: longitude of IPP (degrees) computed at 30s resolution, as the midpoint of IPP longitudes over which roti5m is computed
lat_out: latitude of IPP (degrees) computed at 30s resolution, as the midpoint of IPP latitudes over which roti5m is computed
rot30s: 30s ROT (TECU/min) computed at 30s resolution
%----------------------------------------------------------------------------
The syntax for roti5m is:
[nsecs_out, prn_out, el_out, lon_out, lat_out, roti_5m]=roti5m(nsecs, prn, el, lon, lat, el_mask, rot30s)
The function computes 5-minute ROTI from 30s ROT for each reciever-satellite line of sight
The inputs (described below) are column vectors, except for el_mask which is a scalar:
nsecs: number of seconds from midnight (can be UT or LT)
prn: satellite identifier (can be strings/characters/numeric/numbers)
el: satelite elevation angle (degrees)
lon: longitude of IPP (degrees)
lat: latitude of IPP (degrees)
rot30s: 30s ROT (TECU/min)
The outputs (described below) are also column vectors:
nsecs_out: output number of seconds from midnight (can be UT or LT, same unit as input nsecs) at resolution of 30s
prn_out: output satellite identifier (strings)
el_out: output satelite elevation angle (degrees) computed at 5-minute resolution, as the midpoint of satelite elevation angles over which roti5m is computed
lon_out: longitude of IPP (degrees) computed at 5-minute resolution, as the midpoint of IPP longitudes over which roti5m is computed
lat_out: latitude of IPP (degrees) computed at 5-minute resolution, as the midpoint of IPP latitudes over which roti5m is computed
roti5m: 5-minute ROTI (TECU/min) computed at 5-minute resolution

### Cite As

Daniel Okoh (2023). Programs to Compute ROT and ROTI (https://www.mathworks.com/matlabcentral/fileexchange/129239-programs-to-compute-rot-and-roti), MATLAB Central File Exchange. Retrieved .

##### MATLAB Release Compatibility
Created with R2023a
Compatible with any release
##### Platform Compatibility
Windows macOS Linux