CST Level 1 Land Surveyor Certification Practice

Which of the following governs horizontal coordinates in the United States?

1. NAD 27

2. NAVD 88

3. NAD 83

4. NGVD 29

The correct answer is: NAD 83

The governing system for horizontal coordinates in the United States is the North American Datum of 1983 (NAD 83). This geodetic datum provides a framework for consistent horizontal positioning throughout the country, utilizing a set of reference points across the continent. NAD 83 is utilized for a variety of applications, including mapping, navigation, and land surveying, ensuring that spatial data aligns correctly with geographic and physical features. NAD 83 was developed to replace its predecessor, NAD 27, which had limitations in accuracy and geographic coverage. NAD 83 incorporates advancements in satellite technology and geodesy, providing improved positional accuracy. This is crucial for the precision required in various fields such as civil engineering and land development, where accurate horizontal coordinates are essential for planning and execution. In contrast, the other datums listed serve different purposes. NAVD 88, for instance, is focused on vertical coordinates, establishing a standard reference for elevation across the United States. Similarly, NGVD 29 also pertains to vertical measurements but is replaced by NAVD 88 for accuracy. Thus, while all these datums play important roles in geography and surveying, only NAD 83 specifically governs horizontal coordinates.