Attribute: Vertical datum

Acronym: VERDAT

Code: 185

Attribute Type: E

Expected input:

ID Meaning INT 1 S-4
1 Mean low water springs
2 Mean lower low water springs
3 Mean sea level
4 Lowest low water
5 Mean low water
6 Lowest low water springs
7 Approximate mean low water springs
8 Indian spring low water
9 Low water springs
10 Approximate lowest astronomical tide
11 Nearly lowest low water
12 Mean lower low water
13 Low water
14 Approximate mean low water
15 Approximate mean lower low water
16 Mean high water
17 Mean high water springs
18 High water
19 Approximate mean sea level
20 High water springs
21 Mean higher high water
22 Equinoctial spring low water
23 Lowest astronomical tide
24 Local datum
25 International Great Lakes Datum 1985
26 Mean water level
27 Lower low water large tide
28 Higher high water large tide
29 Nearly highest high water
30 highest astronomical tide (HAT) NEW in S-57 Edition 3.1

Remarks: This attribute is used to specify the datum to which both heights (vertical datum, see S- 57 Part 3) and soundings (sounding datum, see S-57 Part 3) are referred.
When the vertical datum is unknown, such as water areas above locks, the value ‘local datum’ is to be used, and further details may be encoded using ‘INFORM’.
The 0.3m approximation quoted in the “approximate” levels is somehow arbitrary and follows the British example of their definition for “approximate LAT”.

Object Classes that use VERDAT