Depth clearances (Tidal height)
If an area's minimum depth is less than the configured Minimum safe depth, it is considered unsafe. The Auto-route feature will attempt to avoid the area. If avoidance is not possible, the area is marked with a caution symbol.
Auto-routeDepth clearancesThe configured Minimum safe depth is compared with the area's minimum charted depth, based on the depth datum used by the cartography.
Navionics® Autorouting and Dock-to-dock uses the lowest tide level, normally Lowest Astronomical Tide (LAT), plus a preset safety margin.
C-MAP® Easy Routing uses Lowest Astronomical Tide (LAT), or the Mean Lower Low Water (MLLW), depending on region.
Due to atmospheric effects such as high air pressure, wind direction, etc. the tide can be lower than LAT and MLLW. Therefore, it is important that users add a safety margin to their Minimum safe depth and adjust the setting as necessary to allow for current conditions.
For information about configuring the Minimum safe depth setting refer to: Minimum safe depth