National Digital Elevation and Depth Model
The one arc second (~30m) DEMs provide a nationally consistent, medium resolution dataset essential for national and regional scale analysis using the best available source data. It comprises data derived from the Shuttle Radar Topography Mission (SRTM) and LiDAR where available.
Bathymetry is the study and mapping of sea floor topography. It involves obtaining measurements of the depth of the ocean and is equivalent to mapping the topography on land.
Such measurements can be made using:
-Multibeam (swath) echosounders
-Airborne laser measurements (LADS)
-Derived depths from satellite remote sensing