Attribute: Category of zone of confidence in data

Acronym: CATZOC

Code: 72

Attribute type: E

Expected input:

ID	Meaning	INT 1	S-4
`1`	`zone of confidence A1`
`2`	`zone of confidence A2`
`3`	`zone of confidence B`
`4`	`zone of confidence C`
`5`	`zone of confidence D`
`6`	`zone of confidence U (data not assessed)`

Meaning

INT 1

S-4

1

zone of confidence A1

2

zone of confidence A2

3

zone of confidence B

4

zone of confidence C

5

zone of confidence D

6

zone of confidence U (data not assessed)

Definitions - ZOC Table:

1	2	3	4	5
ZOC	Position Accuracy	Depth Accuracy	Seafloor Coverage	Typical Survey Characteristics
`A1`	`ą 5 m + 5% depth`	`=0.50 + 1%d`	`Full area search undertaken. Significant seafloor features detected and depths measured.`	`Controlled, systematic survey high position and depth accuracy achieved using DGPS or a minimum three high quality lines of position (LOP) and a multibeam, channel or mechanical sweep system.`
`Depth (m)`	`Accuracy(m)`
10 30 100 1000	ą 0.6 ą 0.8 ą 1.5 ą 10.5
`A2`	`ą 20 m`	`= 1.00 + 2%d`	`Full area search undertaken. Significant seafloor features detected and depths measured.`	`Controlled, systematic survey achieving position and depth accuracy less than ZOC A1 and using a modern survey echosounder and a sonar or mechanical sweep system.`
`Depth (m)`	`Accuracy(m)`
10 30 100 1000	ą 1.2 ą 1.6 ą 3.0 ą 21.0
`B`	`ą 50 m`	`= 1.00 + 2%d`	`Full area search not achieved; uncharted features, hazardous to surface navigation are not expected but may exist.`	`Controlled, systematic survey achieving similar depth but lesser position accuracy less than ZOC A2 and using a modern survey echosounder, but no sonar or mechanical sweep system.`
`Depth (m)`	`Accuracy(m)`
10 30 100 1000	ą 1.2 ą 1.6 ą 3.0 ą 21.0
`C`	`ą 500 m`	`= 2.00 + 5%d`	`Full area search not achieved, depth anomalies may be expected.`	`Low accuracy survey or data collected on an opportunity basis such as soundings on passage.`
`Depth (m)`	`Accuracy(m)`
10 30 100 1000	ą 2.5 ą 3.5 ą 7.0 ą 52.0
`D`	`Worse than ZOC C`	`Worse than ZOC C`	`Full area search not achieved, large depth anomalies may be expected.`	`Poor quality data or data that cannot be quality assessed due to lack of information.`
`U`	`Unassessed - The quality of the bathymetric data has yet to be assessed.`

ZOC

Position Accuracy

Depth Accuracy

Seafloor Coverage

Typical Survey Characteristics

A1

ą 5 m + 5% depth

=0.50 + 1%d

Full area search undertaken. Significant seafloor features detected and depths measured.

Controlled, systematic survey high position and depth accuracy achieved using DGPS or a minimum three high quality lines of position (LOP) and a multibeam, channel or mechanical sweep system.

Depth (m)

Accuracy(m)

 ą 0.6
 ą 0.8
 ą 1.5
ą 10.5

A2

ą 20 m

= 1.00 + 2%d

Full area search undertaken. Significant seafloor features detected and depths measured.

Controlled, systematic survey achieving position and depth accuracy less than ZOC A1 and using a modern survey echosounder and a sonar or mechanical sweep system.

Depth (m)

Accuracy(m)

 ą 1.2
 ą 1.6
 ą 3.0
ą 21.0

B

ą 50 m

= 1.00 + 2%d

Full area search not achieved; uncharted features, hazardous to surface navigation are not expected but may exist.

Controlled, systematic survey achieving similar depth but lesser position accuracy less than ZOC A2 and using a modern survey echosounder, but no sonar or mechanical sweep system.

Depth (m)

Accuracy(m)

ą 1.2
ą 1.6
ą 3.0
ą 21.0

C

ą 500 m

= 2.00 + 5%d

Full area search not achieved, depth anomalies may be expected.

Low accuracy survey or data collected on an opportunity basis such as soundings on passage.

Depth (m)

Accuracy(m)

ą 2.5
ą 3.5
ą 7.0
ą 52.0

D

Worse than ZOC C

Full area search not achieved, large depth anomalies may be expected.

Poor quality data or data that cannot be quality assessed due to lack of information.

U

Unassessed - The quality of the bathymetric data has yet to be assessed.

Remarks:
To decide on a ZOC Category, all conditions outlined in columns 2 to 4 of the table must be met.

Explanatory notes quoted in the table:

1. ZOC
The allocation of a ZOC indicates that particular data meets minimum criteria for position and depth accuracy and seafloor coverage defined in this Table. ZOC categories reflect a charting standard and not just a hydrographic survey standard. Depth and position accuracies specified for each ZOC category refer to the errors of the final depicted soundings and include not only survey errors but also other errors introduced in the chart production process. Data may be further qualified by Object Class "Quality of Data" (M_QUAL) sub-attributes as follows:

a) Positional Accuracy (POSACC) and Sounding Accuracy (SOUACC) may be used to indicate that a higher position or depth accuracy has been achieved than defined in this Table (e.g. a survey where full seafloor coverage was not achieved could not be classified higher that ZOC B; however, if the position accuracy was, for instance, ą 15 metres, the sub-attribute POSACC could be used to indicate this).

b) Swept areas where the clearance depth is accurately known but the actual seabed depth is not accurately known may be accorded a "higher" ZOC (i.e. A1 or A2) providing positional and depth accuracies of the swept depth meets the criteria in this Table. In this instance, Depth Range Value 1 (DRVAL1) may be used to specify the swept depth. The position accuracy criteria apply to the boundaries of swept areas.

c) SURSTA, SUREND and TECSOU may be used to indicate the start and end dates of the survey and the technique of sounding measurement.

Position accuracy
Position Accuracy of depicted soundings at 95% CI (2.45 sigma) with respect to the given datum. It is the cumulative error and includes survey, transformation and digitizing errors etc. Position accuracy need not be rigorously computed for ZOCs B, C and D but may be estimated based on type of equipment, calibration regime, historical accuracy etc.

2. Position accuracy
Position Accuracy of depicted soundings at 95% CI (2.45 sigma) with respect to the given datum. It is the cumulative error and includes survey, transformation and digitizing errors etc. Position accuracy need not be rigorously computed for ZOCs B, C and D but may be estimated based on type of equipment, calibration regime, historical accuracy etc.

4. Significant seafloor features :
Significant seafloor features are defined as those rising above depicted depths by more than:

	Depth	Significant Feature
`a.`	`<40m`	`2m`
`b.`	`>40m`	`10% depth`

A full seafloor search indicates that a systematic survey was conducted using detection systems, depth measurement systems, procedures, and trained personnel designed to detect and measure depths on significant seafloor features. Significant features are included on the chart as scale allows. It is impossible to guarantee that no significant feature could remain undetected, and significant features may have become present in the area since the time of the survey.

5. Typical survey characteristics
These descriptions should be seen as indicative examples only.

6. Controlled, systematic surveys (ZOC A1, A2 and B)
Surveys comprising planned survey lines, on a geodetic datum that can be transformed to WGS 84.

7. Modern survey echosounder
A high precision single beam depth measuring equipment, generally including all survey echosounders designed post 1970.