What is the primary focus of the National Geodetic Survey (NGS)?

The primary focus of the National Geodetic Survey (NGS) is vertical control surveying, which involves the precise measurement of elevation and the establishment of benchmarks for altitude reference. This is essential for a wide range of applications, including engineering, floodplain management, and various scientific research efforts.

Vertical control is crucial for creating accurate topographic maps and aids in understanding the Earth's surface changes due to natural events, such as erosion or tectonic movements. The NGS provides the necessary data and reference points that help various fields utilize elevation information effectively, ensuring consistency in measurements across different geographical areas.

The other options, while important in their respective fields, do not align with the NGS's primary mission. Marine navigation, satellite communication, and weather forecasting involve different aspects of geospatial science and technology, but they do not focus specifically on vertical control surveying. Thus, the NGS's commitment to establishing a reliable vertical datum makes it a cornerstone of modern surveying practices.