Maps and plans of all land surveys in the Philippines are plotted on standard base maps projected upon spheroidal quadrangles of which spheroid?

• A. Clarke's spheroid of 1866
• B. GRS 80
• C. WGS 84
• D. Airy 1830

Answer: (A)

In surveying, the reference ellipsoid defines the shape of the Earth that coordinates are based on, so the base map grid for plotting surveys is tied to a specific spheroid. For the Philippines, the standard base maps and cadastral plans were established using Clarke's spheroid of 1866, meaning the spheroidal quadrangles are defined on that ellipsoid. This choice reflects historical practice from the American-era mapping, providing a consistent framework for all land surveys; modern ellipsoids like GRS80 or WGS84 are used in GPS and newer systems, but the traditional Philippine base maps remain tied to Clarke 1866.