Final answer:
In the absence of DTED, MSA and Night/NVG altitudes can be determined through alternative elevation data sources like topographic maps, aeronautical charts, or satellite imagery, coupled with a safety buffer dependent on terrain type.
Step-by-step explanation:
When DTED (Digital Terrain Elevation Data) is not available, MSA (Minimum Sector Altitude) and Night/NVG (Night Vision Goggle) altitudes can be determined using other sources of data such as sectional charts and airport publications. MSA is the lowest altitude at which an aircraft can safely fly within a specific sector or area without hitting any obstacles on the ground. It is typically specified for different phases of flight and is based on navigational aids, obstacles, and terrain features.
Night/NVG altitudes are determined based on a variety of factors such as the type of airspace, terrain, obstructions, and navigation aids. Specific altitudes or heights may be published for certain areas to ensure safe operations during night flying or when using Night Vision Goggles (NVGs).