Error in ps_plot(v) that interferogram(1) has no reference area. Also how to add GNSS velocity in Stamps

Hi Everyone, I’m new to PS InSAR. I have following results and faced a problem when executing command
ps_plot(v) but it gave me an error which is


`Could not check if this is Envisat
360482 ref PS selected
Interferogram (1) does not have a reference area
Array indices must be positive integers or logical values.

Error in ps_plot (line 1963)
maxph=phsort(round(length(phsort)*.999));
…`…

how to solve this and also if let’s say i have the GNSS station in my study area and since it has 3 velocity component ‘NS’, ‘EW’ and ‘UD’ in unit mm/year. which one should i use and do i need to convert the velocity from mm/year to any other unit such as cm or meter?

ref_velocity: 3

do i need to convert this mm to any other units let’s say in m and submit it like

ref_velocity:0.03

please find my parameters and errors in screenshot.