I'm trying to compare wrfout file with observations in some locations. I'm pretty sure that all the locations are in the wrf-domain. But when I use wrf_user_ll_to_xy in NCL and wrf.ll_to_xy in wrf-python to get the index of these locations, most of the x values I get are negative. I don't understand why. Is that caused by the projection? I used 'lat-lon' projection.