Which of the following are the main charts used in producing a land/sea survey?

The main charts used in producing a land/sea survey include establishing a levelling datum, which is crucial for ensuring that all elevation data collected during a survey is referenced to a common point. This serves as a foundational reference from which measurements of height or depth are made. The levelling datum allows for the consistent comparison of elevation data across the surveyed area, enabling accurate interpretation and analysis of topographic features.

While other options pertain to important aspects of surveying—such as recording points, establishing horizontal datums, and plotting levels or contours—establishing a levelling datum is fundamental because it determines the basis for all vertical measurements, which are integral to both land and marine surveys. Without a proper levelling datum, the accuracy of all subsequent data would be compromised. Therefore, understanding how to establish this datum is essential for ensuring the reliability of the survey's elevation data.