RLS water level install,IBYC,  9/20/2011
Hap Garritt, Sam Kelsey(MBL)
Nichole Halsey, RonanO’Maitu (Hach)

Used Growler boat at high tide to attach 2 x 6 pressure treated wood underneath pier platform between pilings. Wood will be used to attach the RLS. Wood attached with concrete adhesive and concrete screws.
RLS attached to wood with screws and leveled with shingle shims.
RLS cable attached to 2x4 wood which was secured along concrete. Cable attached to eye screws using cable ties.

Measured distances
Pier deck to sediment bottom, deck near logger down to bottom by floating dock directly downstream of logger/deck railing = 22.45 ft or 6.84 meters
RLS height above pier deck = 33 inches or 0.838 meters

IBYC NAVD88 benchmark/pier deck by datalogger = 2.78 meters, as determined by Trimble high precision GPS.

Year  NAVD88
2016  2.790, new pier joists and decking at IBYC , late spring 2015
2010  2.773
2009  2.811
2008  2.779
2007  2.780

Calculated distances
RLS to sediment bottom = 6.84 + .838 = 7.68 meters
RLS relative to NAVD88 = 3.618 meters

The OTT RLS sensor technology is based on impulse radar. Two antennas are enclosed in a compact housing and transmit pulses toward the water surface, through a Teflon face plate. The transmitting antenna transmits short radar pulses in the 24 GHz ISM band. The receiving antenna receives the pulses reflected from the water surface to determine the distance between the face plate of the radar sensor and the water surface. The time delay from transmission to receipt is proportional to the distance between sensor and water surface. Approximately 16 individual measurements are conducted per second and averaged after 20 seconds to minimize wave influences. 

During late summer and fall of 2018, there were extended periods where the datalogger battery failed and no data was logged. Battery failure seems to coincide with decreased solar  charging due to inclement weather and abnormal high frequency of battery discharge/recharge events.