A method for applying water levels away from a gauge. The area is split into polygons, each assigned a time offset and a range ratio relative to a reference station, derived from tide models or short-term gauges. Soundings inside each zone take the adjusted water level for that zone. Crude zoning shows as steps at zone boundaries; good zoning keeps tide error inside the budget for the survey order.
Tide zoning has the inner bay lagging the gauge by 20 minutes with a range ratio of 1.08.
Also heard as
- tidal zoning
- zoning
- zoned tides
Related terms
Tide correction
The adjustment that removes the height of the tide from measured depths so they refer to chart datum.
Chart datum
The low-water level from which charted depths are measured, set so actual depth is seldom much less than shown.
Bust
A vertical or horizontal mismatch between overlapping lines or surveys that exposes an error somewhere.
ERS
Ellipsoidally referenced survey: depths taken from GNSS ellipsoid heights and converted to chart datum with a separation model.