Zones of Confidence

HSA Systems has recently been awarded a contract to provide Zone of Confidence (ZOC) assessments for all of the hydrographic surveys used in the compilation of New Zealand’s nautical charts from Land Information New Zealand (LINZ). The 18 month contract will include hydrographic survey personnel from Discovery Marine Limited who will undertake a review of 134 nautical charts and approximately 2,000 hydrographic surveys.
Zones of Confidence (ZOC) are quality values applied to hydrographic survey data. Each hydrographic survey used in the production of a nautical chart will be assessed and assigned a value from A to D with a further provision for Un-assessed data. The assessment will take into account positional accuracy, depth accuracy, seafloor coverage and the typical survey characteristics for each survey. The ZOC assessment process is based upon the International Hydrographic Organisations (IHO) S57 CATZOC criteria.
When complete the project will be the first in the world to assign ZOC values to all of its hydrographic surveys used on nautical charts. New Zealand is one of the few countries in the world to provide mariners with depth data quality indicators on all of its charts.