Geomatics: Longitudinal and Cross-Sections
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Questions and Answers

What is the purpose of plotting the formation levels?

  • To mark the boundaries of the project site
  • To form a natural profile of the ground (correct)
  • To determine the total length of the project
  • To evaluate the initial costs of construction

What does a positive RL difference indicate during the calculation of cut and fill?

  • Excess of material requiring removal (correct)
  • No change in ground level
  • Sufficient material available on site
  • Shortage of material for excavation

At what points are levels typically observed for cross-section fieldwork?

  • At regular intervals and changes of slope (correct)
  • At random locations across the site
  • Only at the end of the project
  • Only at the centre-line

How is the RL difference calculated?

<p>Existing RL – Proposed RL (B)</p> Signup and view all the answers

What does the finished level represent in the context of construction?

<p>The level to which the work must be completed (C)</p> Signup and view all the answers

What is the primary purpose of creating longitudinal and cross-sections in construction?

<p>To prepare a survey for planned construction works (B)</p> Signup and view all the answers

What does a longitudinal section represent in surveying?

<p>A vertical section along the centre line of the work (A)</p> Signup and view all the answers

Which instrument is commonly set to establish elevations along a longitudinal section?

<p>Level instrument (A)</p> Signup and view all the answers

How are distances measured in the process of creating longitudinal sections?

<p>Sequentially from the first point to each observed point (B)</p> Signup and view all the answers

What is the relationship between horizontal and vertical scales in plotting a longitudinal section?

<p>The horizontal and vertical scales must be the same (B)</p> Signup and view all the answers

What is one of the first steps in setting out design or proposed levels for a project?

<p>To establish a benchmark from known points (A)</p> Signup and view all the answers

Which of the following is NOT an observed element in longitudinal sections?

<p>Design aesthetics (C)</p> Signup and view all the answers

Why is it important to close levelling work to known benchmarks?

<p>To ensure accuracy and reliability in measurements (A)</p> Signup and view all the answers

What is the purpose of exaggerating the vertical scale in construction designs?

<p>To enable height variations to be readily seen. (A)</p> Signup and view all the answers

When plotting cross-sections, the scales used are typically:

<p>Natural scale, where horizontal and vertical scales are the same. (D)</p> Signup and view all the answers

Which of the following steps is NOT part of preparing a Longitudinal Section?

<p>Joining chainage points with curves. (D)</p> Signup and view all the answers

What should be done to ensure sufficient data is collected for chainage points?

<p>Ensure enough levels are taken slightly more than the total width of the work. (D)</p> Signup and view all the answers

What is meant by 'perpendicular lines' in the context of Longitudinal Sectioning?

<p>Lines drawn at right angles to the datum line at each chainage point. (A)</p> Signup and view all the answers

What is the first step in plotting a Longitudinal Section?

<p>Draw a horizontal line to represent an arbitrary datum. (A)</p> Signup and view all the answers

How should the proposed work be represented on the drawing?

<p>Using exaggerated proportions. (D)</p> Signup and view all the answers

What is an important note regarding the lines in cross-sections?

<p>They should not be drawn as curves since levels are taken at gradual slopes. (D)</p> Signup and view all the answers

Flashcards

Longitudinal Section

A vertical section along the center line of a work, like a road or bridge.

Cross Section

A vertical section taken at right angles to the center line of a work.

Topographical Plan

A plan showing the different heights of the earth's surface in the work area.

TBMs

Known benchmarks used to establish precise elevations.

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Running Chainage

Accumulated horizontal distances from a starting point.

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Setting out formation level

Determining and marking the desired level of a construction element (like a foundation).

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Fieldwork for Levels

The process of observing levels along the longitudinal and cross-sections at regular intervals.

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Level Instrument

Equipment used to measure vertical distances (elevation) during a survey.

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Formation Level

The level at which the construction work is to be excavated or filled to.

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Finished Level

The final level of the completed construction work.

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Cut vs. Fill

The difference between the existing and proposed levels at a given point, determining if material needs to be removed (cut) or added (fill).

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Calculating Cut and Fill

The difference between the existing and proposed levels is calculated to determine the amount of material needed to be removed (cut) or added (fill).

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Fieldwork for Cross-Section

A surveying process similar to longitudinal section, but measuring levels perpendicular to the centerline at regular intervals and changes of slope.

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Vertical Exaggeration

Enlarging the vertical scale of a drawing to emphasize height differences, typically by 10 times the horizontal scale.

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Lowest Value RL

The smallest reduced level (elevation) among the surveyed points along a section.

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Datum Line

A horizontal reference line chosen arbitrarily below the lowest point on the section, used for plotting levels.

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Chainage Points

Locations along a line where levels are taken, marked by distances from a starting point.

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Plotting Longitudinal Section

Drawing the vertical profile of a construction project using levels taken along the center line.

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Plotting Cross Sections

Drawing the vertical profile of a construction project perpendicular to its centerline, using levels taken at specific points.

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Natural Scale

Using equal scales for horizontal and vertical dimensions in a drawing.

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Gradient

The slope or incline of a line connecting two points on a section.

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Study Notes

Geomatrics: Longitudinal and Cross-Sections

  • Types of Plans: Topographical plans, longitudinal sections, cross-sections, and contour maps are used for design and construction.

  • Setting Out Design Levels: Establish benchmarks, position instruments for observations along the section, and record levels at regular intervals.

  • Sectioning: Surveying is needed for road, sewer, drain, and bridge construction, which requires longitudinal and cross-sections.

  • Longitudinal Section: A vertical section along the project's central line, showing its full length.

  • Cross-Section: A vertical section perpendicular to the project's central line at a specific point, showing the section.

  • Data Provided: Gradients for design, quantities for excavation/filling (volumes are calculated), and earthwork depths.

  • Fieldwork for Longitudinal Sections: Establish the center line, measure horizontal distances between level points, record chainages, and ensure consistency with benchmark data.

  • Plotting Longitudinal Sections: Maintain a consistent horizontal scale from site plans, exaggerate the vertical scale (often 10x), establish a datum line below the lowest ground level, plot horizontal chainages, erect perpendiculars, and mark the points.

  • Plotting Cross-Sections: Use a natural scale (horizontal and vertical are equal), plot chainages and levels, join the points to create a section profile, include formation levels, and side slopes.

  • Calculating Cut and Fill: Determine the difference between existing and proposed ground levels; positive values represent 'fill,' and negative values represent 'cut.'

  • Fieldwork for Cross-Sections: Observe the project's centre-line at regular intervals, measure distances corresponding to the different slopes.

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Singapore Polytechnic BE8133 Geomatics PDF

Description

Explore the essential aspects of geomatics focusing on longitudinal and cross-sections. Understand the types of plans used in construction, learn how to set design levels, and familiarize yourself with the fieldwork necessary for effective surveying. This quiz covers critical concepts that are vital in designing infrastructures such as roads and bridges.

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