Cyton impedance calculations

Hi all,
I have a question regarding calculating the impedance on the Cyton board. To my understanding, the ADS1299 uses a current source, that in this case produces 6nA and the voltage is measured. In the OpenBCI_GUI software, the data is buffered and then filtered. First with a notch and afterwards with a bandpass filter ( dataBuffY_filtY_uV). Out of this data, the standard deviation is calculated data_std_uV[Ichan]=std(fooData_filt);
To calculate the impedance for each channel this is done:
float impedance = (sqrt(2.0)dataProcessing.data_std_uV[Ichan]1.0e-6) / cyton.get_leadOffDrive_amps();

I have two things I don't understand:

• Why is the STD used instead of the RMS as described in the comment?
  If the RMS is used it would make sense to calculate the peak value by multiplying with (sqrt(2.0) but this would only be an approximation.

• Which bandpass filter is used to filter the signal?
  30Hz is used as a frequency for the current, so it should be a bandpass at 30hz, right?

Thanks for your help,
David