Mile Marker and US National Grid (USNG) System signs are posted every half mile on the Sac & Fox and Cedar Valley Nature Trails. The USNG System is a grid reference system that uses alphanumeric referencing to provide universal location based services across the United States. In an emergency, the USNG system coordinates and/or mile markers can be used to notify responders of your exact location within the Grant Wood Trails System.
In addition, the signs provide phone numbers for reporting trail maintenance problems and non-emergency situations. Phone numbers may change from sign to sign to reflect changes in jurisdiction. The USNG system coordinates and/or mile markers can be used in these situations to navigate responders to the correct location.