🔍 Key Concepts
• Zone of Confidence (ZOC) categories and what each letter (A1, A2, B, C, D, U) tells you about chart accuracy
• Difference between position accuracy radius and depth accuracy range on the ZOC table
• What the table specifically states for ZOC U in both position and depth columns
💭 Think About
• Look at the row labeled ZOC U on Illustration D055NG and compare it with the rows for ZOC C and D. What is written under position and depth accuracy for U?
• Ask yourself: does ZOC U give any numerical values for position or depth accuracy the way A1–C do, or does it describe something more general about the data quality?
• For each choice, decide whether it assumes a specific accuracy range for both position and depth, or whether it reflects the way ZOC U is described on the chart
✅ Before You Answer
• Confirm exact wording in the ZOC U row, especially under depth accuracy — are any feet, meters, or percentage errors listed?
• Check whether ZOC U implies the data have been fully surveyed, partially surveyed, or not assessed at all.
• Eliminate any answer choices that state a precise depth range and radius if the ZOC U description does not provide corresponding numeric tolerances.