To plan a bridge two characters are needed. One character must carry a [[range pole]], the other a [[dioptra]].
The tiles you stand on from one side to the other are the total count of the distance of the entire span of the bridge. It is not the tiles in between the person with the dioptra, and the person with the range pole.
The character with the range pole does not have to do much besides holding the range pole. To do this activate the range pole, click the ground and select ''Hold'' from the menu. When the action timer starts face the character with the dioptra.