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