How to reach: To reach the tidal bench marks which are accessible only by boat, from the nearest boat launch facilities in Anacortes, Washington, proceed through town on the Highway 20 Spur to the light at Sunset Avenue. Go straight on Sunset Avenue to its terminus in Washington Park. From the boat launch, Armitage Island is approximately 8.5 km (5.3 mi) to the NW across Rosario Strait along the southeastern side of Blakely Island. The bench marks are located along the shore on the southwestern side of the Island. The tide gauge is on a private pier on the west side of the Island.