In comparison with remote sensing techniques, the photo interpretation drainage tile lines generally showed improved accuracy with greater precipitation totals having occurred within the ten day period prior to the photo being taken. This suggests a higher rain value allows for the photo interpreted and remote-sensed tile lines to be in agreement. The photo interpretation tile lines fell within the decision tree analysis area 88.8% of the time. These findings suggest photo interpretation is a useful technique to map unknown drainage tiles. However, existing data or ground-truthing would validate these findings further.