Reconnaissance Survey Methods for Highway Route Selection

What is Reconnaissance Survey?

Reconnaissance survey is a process of examining the general character of an area in order to determine the most suitable route for further investigations. It is mainly used for the purpose of feasibility study, preparation of approximate estimates of quantities and costs, and selection of the most appropriate alternatives for the highway facility.

Benefits of Reconnaissance Survey

Reconnaissance survey offers numerous benefits for highways and other roadways. It helps to identify the most feasible route for further investigations and determine any deviations from the basic geometric standards. Additionally, it enables the preparation of approximate estimates of quantities and costs, which in turn helps to select the most suitable alternatives.

When to Conduct a Reconnaissance Survey

Reconnaissance survey is generally necessary for any new road construction or bypass roads. However, it may not be required for the work consisting of improvements to existing roads.

Conclusion

Reconnaissance survey is an important process for determining the most suitable route for further investigations. It helps to identify any deviations from the basic geometric standards, prepare approximate estimates of quantities and costs, and select the most appropriate alternatives for the highway facility.

Reconnaissance Survey Methods:

The reconnaissance survey methods may be conducted in the following sequence:

a) Study of topographical survey sheets, agricultural, soil, geological and meteorological maps and aerial photography.

b) Aerial photography wherever necessary and feasible, and

c) Ground reconnaissance including another round of serial reconnaissance for inaccessible and difficult stretches, where required.

Study of Survey Sheets and Maps:

Reconnaissance Survey: An Overview

Reconnaissance survey is a preliminary study of the existing topographical features of a particular area. Maps, aerial photographs and stereoscopic techniques are used to identify the best route for a new construction project, such as a road or railway. The survey starts with a study of the maps, then a number of economical alignments are selected based on the criteria such as gradient and curvature of the route, shape of the alignment, avoidance of marshy ground, steep terrains and unstable hill features, connection of important villages and towns, bridging problems, and preservation of the environment. Aerial photographs are taken at a scale of 1:20000 to 1:50000 to supplement the information from topographic maps, and stereoscopic techniques can provide quantitative data and soil and subsoil information.

Selecting the Best Route: Factors to Consider

When selecting the best route for a new construction project, there are several factors to consider. Firstly, the alignment should take into account all the control points and be shortened and more economical compatible with requirements of gradients and curvature. Secondly, the shape of the alignment should be taken into account. Thirdly, the route should avoid marshy ground, steep terrains, unstable hill features and areas subject to severe climatic conditions, flooding and inundation. Fourthly, the route should connect important villages and towns. Fifthly, bridge problems should be taken into account. Finally, ecological balance and preservation of the environment should be a priority.

Aerial Reconnaissance Survey:

Aerial Reconnaissance: A Bird’s Eye View
Aerial reconnaissance is a valuable tool for surveyors, planners, and engineers to gain an overall understanding of the alignments they are considering and the surrounding area. It allows them to quickly identify any potential problems or conflicts, and to make decisions about which alignments should be studied in more detail on the ground. By providing a bird’s eye view of the area, it enables them to make more informed decisions about the best course of action.

Ground Reconnaissance Survey:

What is Ground Reconnaissance?

Ground reconnaissance is the process of exploring an area and collecting detailed information on its terrain by walking, riding or using aerial methods. This information is used to evaluate the area and determine the best possible routes. Instruments such as a compass, Abney level/altimeter, pedometer, aneroid barometer, clinometer, ghat tracer and walkie-talkie sets are used to collect data on ground slopes, maximum gradients, elevation of critical summits or stream crossings, and to locate obligatory points. Additionally, reference pegs can be left to facilitate further survey operations.

How Can Instruments Be Used for Ground Reconnaissance?

Instruments such as a compass, Abney level/altimeter, pedometer, aneroid barometer, clinometer, and ghat tracer can be used to collect data on ground slopes, maximum gradients, elevation of critical summits or stream crossings, and to locate obligatory points. Additionally, reference pegs can be left to facilitate further survey operations. Walkie-talkie sets are also used for communication, particularly in difficult terrain.

What Are the Advantages of Ground Reconnaissance?

Ground reconnaissance provides detailed information on the terrain and can be used to evaluate the area and determine the best possible routes. This type of reconnaissance can also be used to check the accuracy of maps. Additionally, instruments such as a compass, Abney level/altimeter, pedometer, aneroid barometer, clinometer, and ghat tracer can be used to collect data on ground slopes, maximum gradients, elevation of critical summits or stream crossings, and to locate obligatory points.

What Are the Benefits of Using Reference Pegs?

Reference pegs can be left in an area to facilitate further survey operations. This can help to quickly locate points of interest and provide a better understanding of the terrain. Additionally, reference pegs can be used to check the accuracy of maps.

Reconnaissance Survey Reports:

Overview of Reconnaissance Survey

A reconnaissance survey is an initial exploration of an area that is used to collect data and assess the suitability of the area for a specific purpose. The purpose of the survey is to collect information on the area and identify potential alignments that could be used for a project. During the reconnaissance survey, data is collected on the topography, hydrology, soils, land use, and other features of the area.

Preparing a Report

Based on the information collected during the reconnaissance survey, a report should be prepared. The report should include all relevant information collected during the survey and a plan to the scale of 1:50000 showing the alternative alignments studied along with their general profile and rough cost estimate. It should also discuss the merits and demerits of the different alternatives to help the selection of one or more alignments for detailed survey and investigation.

Analyzing Data Collected

The data collected during the reconnaissance survey must then be analyzed to identify potential alignments for the project. The data should be used to create a plan to the scale of 1:50000 showing the alternative alignments studied along with their general profile and rough cost estimate. This plan should include the general profile of the various alignments studied and provide rough cost estimates of each option.

Discussing Merits and Demerits of Alternatives

The report should also include a discussion of the merits and demerits of the different alternatives. This discussion should help in the selection of one or more alignments for detailed survey and investigation. The merits and demerits should be discussed in regards to the general profile of the alignments, the rough cost estimate, and how the alignments fit into the overall project.