118 U. S. COAST AND GEODETIC SURVEY 
Los Angeles La Jolla Factors for correction La Jolla 
Date LW LW MLW Veg | MEN 
below DLQ below DLQ LW DLQ below DLQ below 
HTL HTL HTL HTL 
1946 Feet Feet Feet Feet Feet Feet Feet 
January _-_--- 1. 84 1.11 1. 76 1. 08 1. 022 0. 856 1, 80 0. 92 Pe, 1? 
Marc haere 1. 91 0. 83 1. 85 0. 79 0. 984 1. 145 1. 82 0. 90 PA UP 
Mayas sso 22 1. 90 1. 03 1. 87 1. 00 0. 989 0. 922 1. 85 0. 92 2.70 
July ese Ss 1. 88 1.16 1.79 1. 13 1. 000 0. 819 1. 79 0. 93 2. 72 
September - - - 1, 0. 81 io 7 0. 76 1. 016 iL 17} 1. 80 0. 89 2. 69 - 
November _ - - 1. 88 ie ii 1. 83 1. 09 1. 000 0. 856 1. 83 0. 93 2. 76 
The procedure is exactly similar to that used in deriving mean lower low water from 
a year of observations. In connection with that example it was found that for epoch 
1928-1946 low water below half-tide level at Los Angeles is 1.88 feet and DLQ is 0.95 
foot. The primary determination of mean lower low water below half-tide level at 
La Jolla was found to be 2.73 feet. The values derived for the six months in the last 
column of the table above thus differ from the primary value by not more than 0.04 
foot. The example for Neah Bay and Seattle follows. 
Seattle Neah Bay Factors for correction Neah Bay 
Date LW Liw MLW MLLW 
below DLQ below DLQ LW DLQ below DLQ below 
HTL HTL ATL HTL 
1946 Feet Feet Feet Feet Feet Feet Feet 
January ——-_-- 3. 81 3. 65 2. 74 1. 1. 003 0. 778 2 1. 54 4. 29 
Miarchis=2522 3. 74 2. 46 2. 72 1. 35 1.019 1. 150 4, 0 1755 4, 32 
IMiaiyn ees 3. 91 2.92 2. 84 Ie 7a 0. 977 0. 973 Deus 1. 66 4. 43 
Duly Ae 3. 90 3. 33 2. 84 1. 82 0. 979 0. 853 2.78 155 4. 33 
September _ - - 3. 79 2. 42 2.02 133 1. 008 1. 174 2: 1. 56 4. 30 
November __ - 3. 81 3. 04 2. 70 1. 84 1. 003 0. 934 Dini 1. 72 4. 43 
The best determined value for mean lower low water below half-tide level at Neah 
Bay for the epoch 1930-1948 is 4.40 feet. The six values determined in the last 
column of the table above, on the average differ by 0.07 foot from the best determined 
value, with 0.11 foot the greatest difference. It may therefore be taken that in general 
a month of observations will determine the value of mean lower low water below 
half-tide level within 0.1 foot when compared with a suitable primary tide station. 
Day.—In determining mean lower low water from one day of observations, one 
observed value of lower low water at the secondary station is compared with one 
observed value at the primary station. Disturbances in regularity of rise and fall 
by meteorological conditions will therefore be less likely to balance out than in periods 
of several days. The accuracy attainable is illustrated below for every fifth day of 
the month of July 1946 for La Jolla using Los Angeles as primary station. 
a 
