What is the extent of zone I in the Philippine Plane Coordinate System, given its central meridian of 117°?

• A. 114°00' to 116°30'
• B. 116°00' to 118°30'
• C. 117°30' to 120°30'
• D. 118°00' to 120°30'

Answer: (B)

In the Philippine Plane Coordinate System, each zone is defined by a fixed longitudinal extent around its central meridian, so maps within a zone share a common projection reference. For Zone I, the central meridian is 117°. The standard boundaries for this zone are set so the zone spans a specific width around that meridian, giving a practical, consistent area for projection. The extent from 116°00' to 118°30' encompasses 2°30' of longitude and places 117° squarely within the zone, which aligns with how Zone I is defined in the PCS.

Other extents would shift the boundaries enough that either the central meridian would be at a different position relative to the zone or the zone would cover a different region, which doesn't match Zone I's established definition. So the correct extent is 116°00' to 118°30'.