Fundamentals of Surveying (FS) Practice Exam

The scale factor in a transverse Mercator projection mainly varies with which of the following?

1. Longitude

2. Latitude

3. Both latitude and longitude

4. Meridional arcs

The correct answer is: Longitude

In a transverse Mercator projection, the scale factor is primarily affected by longitude, specifically due to the way the projection is designed to minimize distortion along the central meridian. The transverse Mercator projection displays the Earth’s surface on a two-dimensional plane where the central meridian appears as a straight line. As you move away from this central meridian, the scale factor begins to increase or decrease, leading to distortion in the dimensions of the features on the map. The scale factor reaches its minimum value exactly on the central meridian and increases as you move east or west from this line. In other words, the scale remains true along the meridian but varies as you travel towards the edges of the mapped area. Although latitude also plays a role in determining the projection's properties, the most significant variations in scale occur with changes in longitude. This principle is critical for cartographers and surveyors who must account for accuracy in distance calculations on maps made using the transverse Mercator projection. Understanding how scale factors vary with longitudinal position helps ensure more accurate representations of geographic data.