Route surveys – appropriate contouring method for a long linear project For preparing a contour plan along a proposed route (such as a road, canal, or pipeline), which method is most appropriately used?

Introduction / Context:
Route surveys extend along a narrow corridor for long distances. The objective is to understand the ground profile and lateral variation of levels to design grades, cut-and-fill, and drainage. Choosing the right contouring approach ensures efficient data collection and reliable longitudinal and transverse information. This question asks for the most suitable method for such linear projects.

Given Data / Assumptions:

• The alignment is known or roughly staked on ground.
• We need elevations along the centerline and at offsets to a certain width.
• Speed and economy are important over large lengths.

Concept / Approach:

The method of cross profiles involves running a longitudinal profile along the route and taking regular cross-sections (at fixed intervals and at critical points) out to the required offset distance. Levels from these profiles are then used to draw contours for the corridor. This method concentrates effort where it matters most—the linear strip—rather than gridding a large area as in the indirect/grid method. Method of squares suits compact sites; trace contour is used to locate a particular contour line rather than mapping a corridor comprehensively.

Step-by-Step Solution:

Verification / Alternative check:

Design workflows for roads and canals universally rely on cross-sections for earthwork computation and drainage design, confirming the suitability of cross profiles for contouring a route.

Why Other Options Are Wrong:

Method of squares: efficient for compact areas, not long corridors.

Trace contour: finds a single contour, not a full contour plan.

Indirect grid method: wastes effort far from the route; not optimized for linear projects.

Common Pitfalls:

Spacing cross-sections too widely; missing critical points like culverts and intersections; neglecting lateral drainage considerations.

Final Answer:

Method of cross profiles