Summary of Iho Minimum Standards for Hydrographic Surveys

SUMMARY OF IHO MINIMUM STANDARDS FOR HYDROGRAPHIC SURVEYS

ORDER Special 1 2 3 Examples of Typical Harbors, berthing areas, Harbors, harbor Areas not described in Offshore areas not Areas and associated critical approach channels, Special Order and described in Special channels with minimum recommended tracks Order 1, or areas up to Order, and Orders 1 and underkeel clearances and some coastal areas 200 m water depth 2 with depths up to 100 m Horizontal Accuracy 2 m 5 m + 5% of depth 20 m + 5% of depth 150 m + 5% of depth (95% Confidence Level) Depth accuracy for a = 0.25 m a = 0.5 m a = 1.0 m Same as Order 2 Reduced Depths (95% b = 0.0075 b = 0.013 b = 0.023 Confidence Level) (1) 100 % Bottom Search Compulsory Required in selected May be required in Not applicable areas selected areas System Detection Cubic features > 1 m Cubic features > 2 m in Same as Order 1 Not applicable Capability depths up to 40 m; 10% of depth beyond 40 m Maximum Line Not applicable, as 3 x average depth or 25 3-4 x average depth or 4 x average depth Spacing 100% search m, whichever is greater 200 m, whichever is compulsory greater Horizontal control Primary control: 1 Same as Special Same as Special Same as Special part in 100,00 for ground survey methods; 10 cm at 95% confidence level for geodetic satellite methods. Secondary control: 1 part in 10,000 for ground survey methods; 50 cm for geodetic satellite methods. Position of fixed aids 2 m at 95% confidence Same as Special 5 m at 95% confidence Same as Order 2 to navigation and level level features significant to navigation Position of Natural 10 m at 95% 20 m at 95% Same as Order 1 Same as Order 1 Coastline confidence level confidence level Mean position of 10 m at 95% Same as Special 20 m at 95% Same as Order 2 floating aids to confidence level confidence level navigation Position of 10 m at 95% 20 m at 95% Same as Order 1 Same as Order 1 Topographical confidence level confidence level Features Tidal Observations Error not to exceed ± 5 Error not to exceed ± Same as Order 1 Same as Order 1; no cm at 95% confidence 10 cm at 95% tides applied in depths level confidence level > 200 m Bottom Sampling 10 times line spacing; 10 times line spacing Same as Order 1 Same as Order 1; not denser in anchorages required in depths > 200 m Tidal Stream Measure at 3 and 10 m Same as Special Done only if they are of Same as Order 2 Observations below the surface. sufficient strength to Observations at hourly affect surface intervals for not less navigation. than 15 days; 29 days or more preferred. Measure to nearest 0.1 knot and 10 degrees at 95% confidence level. (1) To calculate the error limits for depth accuracy the corresponding values of a and b listed above have to be introduced into the formula ±√(a squared + (b *d) squared) with: a constant depth error, i.e. the sum of all constant errors b*d depth dependent error, i.e. the sum of all depth dependent errors b factor of depth dependent error d depth