 It is easy to see immediately that a right-angled triangle "ABC" has been created.The length "BC" is the "alargar" (distance from intended course), which can be measured as 46 miles (this can be visually seen as two grid squares plus a bit, that is 20m + 20m and a little bit which can be assessed as 6m by using the dividers and the 20m bar scale).The length "AC" is the "avanzar" (distance made good), which is 111 miles – visually, five grid squares and a bit, or (20 × 5) + 11, measured by dividers and scale again.