I'm trying to simulate a satellite tracker. With ode45 I have de state of the satellite for each time and then convert position to Azimuth-Elevation local coordinates. If the object enters in the field of view (expressed as a mask of Az-El), the integration stops and changes the step to a smaller one in order to obtain more points inside. I'm trying to use an 'Events' function, which compares de Az-El of the satellite with the radar's mask. The problem is ode45 detects an event when it's not supposed to, and vice versa.

I discarded the transformation to angular coordinates as the origin of the problem, and i tried to reduce the step size.Az-El plot

load("maskmin.mat")
load("maskmax.mat")
Azmaskmin = maskmin(:,1);
Elmaskmin = maskmin(:,2);
Azmaskmax = maskmax(:,1);
Elmaskmax = maskmax(:,2);
t_total = [];    y_total = [];
az_total = [];   el_total = [];
t_actual = t0;   y_actual = y0;
options = odeset('RelTol',3e-14,'AbsTol',3e-14,'Refine',10,'NormControl','on',...
    'Events', @(t,y) eventos_radar(t, y, lat_radar,...
                lon_radar, alt_radar,Azmaskmin,Azmaskmax,Elmaskmax,Elmaskmin));
aze = [];
ele = [];
yee = [];
tee = [];
% Principal loop
r1 = 100; % Big step
rt = 10; % Small step
dt = r1; % Initial condition isn't inside FOV
while t_actual < tf - dt
     [t, y, te, ye] = ode45(@(t,y)ecuacion_movimiento(t, y, mu),...
            [t_actual:dt:tf], y_actual, options);
     t_total = [t_total; t];
     y_total = [y_total; y];
     % Update next integration
     t_actual = t(end);
     y_actual = y(end,:)';
     % Event check
     if ~isempty(ie)
         if dt == r1
             dt = rt;
             fprintf('Entrance in t = %.2f segundos\n', t_actual);
         elseif dt == rt
             dt = r1;
             fprintf('Exit in t = %.2f segundos\n', t_actual);
         end
         t_actual = te(end);
         y_actual = ye(end, :)';
     end
end
% Procesing results
procesar_resultados(t_total, y_total, lat_radar, lon_radar, alt_radar,...
        Azmaskmin,Azmaskmax,Elmaskmax,Elmaskmin);
function [value, isterminal, direction] = eventos_radar(t, y, lat_radar,...
    lon_radar, alt_radar,Azmaskmin,Azmaskmax,Elmaskmax,Elmaskmin)
[az, el] = calcular_az_el(y(1:3)', lat_radar, lon_radar, alt_radar, t);
if az>=Azmaskmax(1) && az<=Azmaskmax(end)
     el_min = interp1(Azmaskmin, Elmaskmin, az);
     el_max = interp1(Azmaskmax, Elmaskmax, az);
     value = [el_max - el, el - el_min];
     isterminal = [1 1]; % Detect changes of sign
else
     value = [Elmaskmax(1) - el, el - Elmaskmax(1)];
     % Elmaskmax(1) is the El value from the FOV corner in order to get continuous values of 'value' when the object is             % outside
     isterminal = [0 0]; % Ignores changes of sign
end
direction = [0 0];

'Value'-time: The left plot is using the y_total values once the simulation stops, and the rigth plot is using the values of the y that the event function receives from the ode 45.

Anyone knows what is going on? Any help is welcome!!