Using the spline to project highway alinement on the topographic map compiled 
by photogrammetric methods. The aerial photographs of the route mapping pho- 
tography are examined under stereoscopes at the same time to ascertain valuable 
information by their interpretation which cannot be represented on the topo- 
graphic map. Several trial positions for the alinement are compared. Then 
a mathematical description of the selected alinement is computed in prepara- 
tion for staking it on the ground.