All data are in 75th Meridian Time. The hours on the day are numbered consecutively from 0 hour (midnight) to 23 hour (11 p.m.); 12 hour is Noon and all hours greater than 12 are in the afternoon.
Predicted tidal elevation are reckoned from the same datum plane as used for the nautical charts of the locality. To find the actual depth of water at any time, the height of the tide as shown in the tide table should be added to the depth of water as shown on the chart. If the height of the tide is preceded by a minus sign it should be subtracted from the chart depth.
The datum for tidal elevations at Balboa (Pacific) is MEAN LOW WATER SPRINGS, which has been determined by the U.S. Coast & Geodetic Survey as being 8.4 feet below Mean Sea Level at Balboa. Based on the mean elevations for tidal planes for the 19 year period, 1916-1934 , MEAN LOW WATER SPRINGS at Balboa is equivalent to -7.617 feet Panama Canal Precise Level Datum.
The datum for tidal elevations at Cristobal (Atlantic) is MEAN LOW WATER which has been determined by the U.S. Coast & Geodetic Survey as being 0.4 foot below Mean Sea Level at Cristobal. Based on the mean elevations of tidal planes for the 19 year period, 1916-1934, MEAN LOW WATER at Cristobal is equivalent to -0.384 foot Panama Canal Precise Level Datum.