Best practice with a plane table: how should rays be drawn from stations? When plotting on a plane table from an instrument station, which practice yields the most reliable intersections and clean plotting?

Difficulty: Easy

Correct Answer: Draw only short rays sufficient to contain the required points

Explanation:


Introduction / Context:
Plane tabling integrates observation and plotting. Ray drawing from stations must be disciplined to keep the sheet legible and to maintain accuracy in intersections, resections, and radiations. Excessively long rays clutter the sheet and complicate later work.


Given Data / Assumptions:

  • Proper orientation, levelling, and centering of the plane table are performed.
  • Lines (rays) are drawn to represent directions to detail points.
  • Good drafting hygiene is required for clarity and precision.


Concept / Approach:

The recommended practice is to draw only short rays just long enough to mark the required point. This limits overlapping, maintains readability, and focuses attention on the usable segment of each ray near the plotted point. Continuous full-length rays from multiple stations create dense linework and can cause confusion or misidentification during intersection and checking.


Step-by-Step Solution:

Sight the detail with the alidade and mark a short ray in the correct direction.Plot the point where the short rays intersect (intersection method) or at a scaled distance (radiation method).Repeat only as necessary, avoiding unnecessary extensions across the sheet.


Verification / Alternative check:

Standard plane table manuals explicitly advise short rays to reduce clutter and avoid masking of subsequent work.


Why Other Options Are Wrong:

Long continuous rays (A) clutter the drawing; avoiding second rays (C) defeats intersection accuracy; indiscriminate distant sights (D) can degrade precision due to atmospheric and plotting limits; constant redrawing (E) is inefficient and risks wear on the sheet.


Common Pitfalls:

Forgetting to re-orient between stations; failing to label rays lightly to keep the sheet tidy.


Final Answer:

Draw only short rays sufficient to contain the required points

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