Updated dispersion check for better handling of 'sine' and 'contsine' waveforms.

gprMax/grid.py

@@ -125,6 +125,10 @@ def dispersion_check(G):
                 waveformvalues[timeiter.index] = waveform.calculate_value(timeiter[0], G.dt)
                 timeiter.iternext()
 
+        if waveform.type == 'sine' or waveform.type == 'contsine':
+            maxfreqs.append(4 * waveform.freq)
+        
+        else:
             # Calculate magnitude of frequency spectra of waveform
             power = 20 * np.log10(np.abs(np.fft.fft(waveformvalues))**2)
             freqs = np.fft.fftfreq(power.size, d=G.dt)