Longitude profiles of the 511 keV emission from ²⁶Al, ⁴⁴Ti, and ⁵⁶Ni positrons (top, middle, and bottom panel respectively). Black, blue, and green curves correspond to transport configuration A, B, and C respectively. The red curves are the profile of a 511 keV sky model obtained from model-fitting to the INTEGRAL/SPI observations (the dashed part representing the longitude range over which the intensity is poorly constrained). The given intensities correspond to parapositronium annihilation only and were normalised to a positron injection rate of 10⁴³ e⁺/s, with a positronium fraction of 0.95. The profiles were integrated over a π/9 rad latitude band centred on the Galactic plane.