Heterodyne mapping is done by offset pointing the telescope. Especially for larger maps, OTF mapping is more efficient for larger maps because a common reference position is used for all the cells in each row.
uip>  for i 1 to 3   uip>    rao /map (i-2)*15   uip>    for j 1 to 3   uip>     deco /map (j-2)*15   uip>     oo_scan N /designated_off  uip>    next   uip>  next  OFF ONuip>  rao /map -15   uip>  deco /map -15   uip>  oo_scan N /designated_off  uip>  deco /map 0   uip>  oo_scan N /designated_off  uip>  deco /map +15   uip>  oo_scan N /designated_off