Furthermore, observed depth = height of tide - drying height.Ĭharted depths or soundings are indicated on the charts by contour depths (areas with different colour denoting a certain depth level), contour lines and spot depths. The image above also shows that observed depth = charted depth + height of tide, and note that observed depth is synonymous with depth of water. Check for possible notes under the Chart Title. Note, planes of reference are not exactly as shown above for all charts. ![]() The term clearance height is synonymous with vertical clearance. ![]() The depths and heights in the chart need a plane of reference: the chart datum (CD).ĭepths are usually described with respect to low water reference planes (yielding lower charted depths, which are safer), and heights are shown with respect to high water reference planes (again, yielding lower vertical clearances on the chart, which are safer).Īs such, the chance that the observed depth or vertical clearance beneath a bridge is smaller than the charted depth or height is rather small.
0 Comments
Leave a Reply. |