Elevation-Derived Hydrography READ Rules: Additional Elevation-Derived Hydrography Treatments and Elevation Specific Features
The following describes treatments and additional features that should be applied during the acquisition of sea/ocean, and other waterbody features and should be taken into consideration as treatments for the depiction of waterbodies. The treatments and additional features can also be used to convey additional information about the level of confidence for elevation data in certain acquisition area.
Island
A permanent island is an area of exposed land, surrounded by water. These are features to be collected in and of themselves but also are a treatment. Islands need to be erased from lake/pond features.
Delineation
Lake/Pond
The minimum size for islands within lake/pond is 0.12 acres (500 square meters).
For lidar base specification hydroflattening, permanent islands 1 acre (4,000 square meters) or larger shall be delineated within all waterbodies and excluded from hydroflattening.
Sea/Ocean
The minimum size for islands within sea/ocean is 1 acre (4,000 square meters).
For lidar base specification hydroflattening, permanent islands 1 acre (4,000 square meters) or larger shall be delineated within all waterbodies.
Stream/River
The minimum size for islands within stream/river is 0.12 acres (500 square meters).
For lidar base specification hydrographic breakline, permanent islands 1 acre (4,000 square meters) or larger shall be delineated within all waterbodies.
Island/Sandbar
Intermittently/partially submerged islands or parts of islands are submerged at the time of collection (figure 35). These are most often found in coastal areas because of tidal variations during the collection, or in rivers collected while at a high flow. If island/sandbar is disconnected from the shore or is visible at the time of collection, then treat as an island (remove from lake/pond or sea/ocean feature). Otherwise, treat as shoreline.
