Δv values measured at different observation angles with a double-Gaussian fit at a redshift z = 0.05. Each individual measurement covers a solid angle of 0.013 sr and the colour code indicates the measured Δv value. We choose the Hammer-projection to represent the observation points on the surface. The longitudes represent the azimuth angle ϕ which is measuring the observation angle relative to the central bar of the galaxy. ϕ = 0° and ϕ = ±180° correspond to an observation parallel to the bar and an azimuth angle ϕ = ±90° to an observation perpendicular to the bar. The latitudes represent the inclination of the observer. At an inclination of θ = 90° the galaxy is observed edge-on whereas at θ = 0° and θ = 180° one sees the galaxy face-on.