What is meant by highway survey?

Surveying is an operation in the civil engineering domain that requires collecting and identifying data regarding an area of land and topography. The data that is collected can be helped to plan and undertake the construction process. Civil engineers perform surveys to gather three-dimensional information regarding a particular area. Engineers specify several points on the surface of the earth and relationship between points, and the distance and angles between the points are evaluated. The data from this evaluation guides in drawing plans regarding buildings and structures.

Highway surveys are a specific part of the traditional civil survey that uses the same concepts and techniques. Highway survey is a professional way of land survey, which are usually undertaken by civil engineers and professional authorities in various parts of countries, which forms the basic phase in planning a highway or a road project for transportation purpose. The objective of highway survey is to locate a perfect alignment of roadways that serves as a primary source of maximum transportation facilities. Besides this, a proper highway survey provides an accurate location and contour layout data of road, utilities, drainages, overhead wires, near by structures, buildings, and other features.

Technology used in highway surveying

With the rise of power of technology, it serves as a boon in performing surveying. Some of the technological advancements which are used in surveying are:

Computer aided design (CAD)

After gathering information by engineers regarding the terrain or land details, and area topology, the CAD turns these data into visual representation like a three-dimension model, or a map. Unlike sketching and engineering drawing, CAD models provide precise visual representations.

Global positioning system (GPS)

The gaps serves as a virtual map and pin points exact location of points regarding land and topology details. The GPS not only shows the information regarding the present survey area but provides a over all domain map of near by areas.

Aerial photogrammetry

Aerial photogrammetry refers to the use of drones to perform aerial photography regarding a particular geographical location from multiple angles and combining these images to form a 3d image.

Point cloud modeling

This method uses laser technology to place multiple points in the area or land surface that engineers need to collect information of. Once the data points are marked they are brought together using the point cloud modeling to generate accurate 3d models.

Phases of highway surveys

There are basically fives phases that are followed while performing a highway survey. They are outlined below.

Map study

This is the primary step before carrying out the actual surveying process. A preliminary study of the geographical area and land topography is done by analyzing maps in detail. Map study provides engineers with the various artificial and natural features regarding a particular location. Different routes and nearby roadways can be well analyzed by map study. The data collected by such analysis leads to the proper decision regarding highway layout and construction, which will aid in maximum transportation.

Reconnaissance survey

In this phase, a team of professionals heads towards the area with specific surveying instruments like tangent clinometer, Abney level, compass, etc. They perform a rough survey regarding the area to be used. This study is performed as an intersection based on the map study. The routes analyzed through surveying, if found impossible, are excluded from the map plan. In the end, engineers are left with information and routes which can be analyzed and carried forward in the next phase.

Preliminary survey

In this phase of the survey, the data and the routes which are acquired through the rough survey are further processed and surveyed in depth. in this phase, advanced surveying instruments are used like chains, theodolite, levels for performing leveling, etc. Advanced technologies like photogrammetry and GPS data collections are used in the process. All the data are collected and analyzed in detail, A best alignment and construction plan is finally decided.

In this stage, different kinds of information are obtained using various studies like soil investigation, cross-sectioning, profiling, etc.

Location survey

In this phase, all the data collected in the previous phases, are assembled in the form of a construction project document. This documents the precise data points, images, 3d models, drawings, and sketches of the geographical area which will initiate the start of construction project.

Concept of highway alignment and survey

Highway alignment is the position of the centerline of the highway on the land surface. The highway alignment surveys usually include horizontal alignment, cross-section angle, and vertical alignments. Highway alignment is usually provided for the safety and protection of highways. Once the alignment is completed and the construction project is initiated, the alignment cannot be changed. Hence, it is crucial for the engineers to carry on the highway alignment in a proper manner. Else, it leads to one or more of the following disadvantages:

• Increase in labor and construction cost
• High maintenance costs
• Repeated frequency of maintenance and repairs
• increased vehicle operation cost
• High accident probability

Context and Applications

This topic is widely taught in various undergraduate and postgraduate degree courses of:

• Bachelors of Technology in Civil engineering
• Masters of Technology in Civil engineering
• Masters of Science in Highway technology
• Masters of Science in Construction of building

Practice problems

Q1) Which of the following instrument is used in preliminary survey?

1. Theodolite
2. Tangent clinometers
3. Counties
4. None of these

Answer: Option a

Explanation: In the preliminary survey, advanced surveying instruments are used like theodolite, chains and levels.

Q2) Which of the following surveying, professionals perform a rough survey?

1. Plane survey
2. Reconnaissance survey
3. Location survey
4. Geodetic survey

Answer: Option b

Explanation: In the reconnaissance survey, professionals and engineers perform a rough survey and estimation.

Q3) Which of the following is a surveying instrument?

1. Counties
2. Level
3. Compass
4. Both b and c

Answer: Option d

Explanation: Both compass and level are surveying instruments.

Q4) What is photogrammetry?

1. Take visual pictures of federal areas
2. Takes photos from multiple angles and combine it to form a 3d image
3. Placing data points on the surface of earth and create a 3d visual rerpresentation
4. None of these

Answer: Option b

Explanation: Photogrammetry refers to taking multiple photographic shots from different angles and combining the photos to form a single 3d model.

Q5) What is the final phase of a highway survey?

1. Geodetic survey
2. Location survey
3. Reconnaissance survey
4. Both a and b

Answer: Option b

Explanation: Location survey is the final phase of a highway survey.