What is the required horizontal accuracy for a map larger than 1:20,000?

For a map scale larger than 1:20,000, the required horizontal accuracy is designed to ensure that the positional accuracy of features on the map meets user needs for reliability, especially given that larger scales represent smaller areas in greater detail.

In this case, the correct answer emphasizes the standard of achieving a horizontal accuracy of 1/30 (.033). This means that for every 30 units measured on the ground, the positional accuracy of a feature on the map can tolerate an error of 1 unit. This level of accuracy is suitable for maps used for detailed planning or analysis where precision is essential.

Maps that are larger than 1:20,000 require tighter accuracy controls because any positional errors can significantly impact the interpretation and use of the map for things such as urban planning, environmental management, or emergency response planning.

This is why 1/30 (.033) is established as the standard, as it strikes a balance between usability and realistic accuracy in a mapping context where more detailed representations of geography are needed.