- What is Surveying?
Surveying is the process of measuring, mapping and analyzing physical features on the Earth’s surface. It involves taking precise measurements of angles, distances and elevations in order to create plans, maps and diagrams which accurately depict the physical features of an area.
- Steps Involved in Making Plans
Surveying involves several steps in order to make a plan or map. These include the selection of a suitable scale, the collection of data from the field, the plotting of the data onto a map or plan, and the preparation of a report of the survey.
- Selecting a Suitable Scale
The scale of a map or plan is an important factor when surveying an area. The scale should be determined based on the size of the area to be surveyed and the level of detail required in the plan. It should also be taken into consideration the size of the area and the size of the objects that need to be measured.
- Collecting Data from the Field
The surveyor will then collect data from the field using the appropriate tools and equipment. This may include various types of instruments such as total stations, theodolites, GPS receivers, and even drones. The surveyor will measure angles, distances and elevations of various points in the area.
- Plotting the Data onto a Plan
Once the data has been collected from the field, it must then be plotted onto a map or plan. This involves transferring the data from the field onto a two-dimensional representation of the area. The surveyor must take into consideration the scale of the area, the size of the objects being measured, and the accuracy of the data being plotted.
- Preparing a Report of the Survey
Finally, the surveyor must prepare a report of the survey. This report should include a summary of the survey, a description of the area surveyed, and a detailed analysis of the data collected. The report should also include any recommendations or conclusions that have been made based on the survey.
Mapping Methods in surveying:
Applying Necessary Corrections to Measurements
After completing the field work in chain and compass surveying, the office work begins with applying the necessary corrections to the measurements taken. This includes corrections for the curvature of the earth, atmospheric refraction, and any errors that may have been made during the survey.
Drawing Index Plan
The next step is to draw an index plan. This plan shows the overall layout of the survey and identifies the measurements taken. It also serves as a reference for the other steps in the office work.
Selecting Scale
The third step is to select a suitable scale for the plan. The scale should be chosen depending on the purpose of the survey and the accuracy required. It should also be large enough to show all the features in the survey area.
Selecting Orientation
The fourth step is to select an orientation for the plan. This will determine the direction the survey lines will run in. The orientation should be chosen to best suit the purpose of the survey.
Drawing Network of Survey Lines
The fifth step is to draw a network of survey lines. This will connect the measurements taken in the field, and form the basis of the plan. The lines should be as accurate as possible, as any errors will be propagated throughout the plan.
Distributing Closing Error
The sixth step is to distribute the closing error. This is the difference between the starting and ending points of the survey. The error should be distributed throughout the plan, so that the final plan is as accurate as possible.
Filling in the Details
The seventh step is to fill in the details of the plan. This includes adding symbols for buildings, roads, rivers, etc. Any measurements taken in the field should also be marked on the plan.
Colouring the Map
The eighth step is to colour the map. This is done to make the plan easier to read and interpret. Different colours can be used to indicate different features, such as roads and rivers.
Drawing Graphical Scale
The ninth step is to draw a graphical scale. This is used to measure distances on the plan, and should be as accurate as possible. The scale should be chosen to best suit the purpose of the survey.
Writing Index
The final step is to write an index. This is a list of the features shown on the plan, and should include their locations. It should also include any measurements taken in the field.
1. Applying Necessary Corrections to Measurements
Compass Survey Corrections
Compass survey is an important survey technique which is used to measure angles between lines. However, this method is susceptible to various errors caused by external factors, such as the attraction of local magnetic fields, and the effects of tapes and chains. To ensure accurate results, it is essential to apply the necessary corrections to the survey lines measured.
Tape and Chain Corrections
Tape and chain corrections are necessary to account for variations in the length of the measuring tape or chain used in compass survey. These corrections are applied to compensate for the slight variations in the length of the measuring device due to temperature, humidity and other factors.
Corrections for Local Attraction
The measurement of angles in compass survey is also affected by the local attraction of magnetic fields, which can cause the compass needle to deviate from the true north. To compensate for this effect, corrections for local attraction must be applied to the survey lines measured. This correction is determined by taking readings from a base line and using the differences in the readings to calculate the amount of local attraction.
2. Drawing Index Plan
What is a Rough Sheet Index Plan?
A Rough Sheet Index Plan, also known as a Key Plan, is a drawing of a network of survey lines that shows the approximate shape and distances of an area to be plotted. This plan is used to identify the shape of the area to be mapped. The plan does not need to be drawn to exact scale and measurements.
3. Selecting Scale
How to Select a Survey Scale
Selecting the right survey scale for your project is an important consideration. It can help ensure accurate data collection and reliable results. The scale should be selected based on the type of survey being conducted. For example, if a survey is measuring distances, then a larger scale would be more appropriate. Additionally, the size of the paper and the largest linear measurement in the field should also be taken into account when selecting the scale. Generally, it is recommended to choose the largest scale possible.
4. Selecting Orientation
Steps for Determining Map Orientation
- Deciding the Map Position:
When creating an index map, it is important to decide the position of the map on the drawing sheet. The map should be placed in the middle of the drawing sheet with its larger dimension running along the length of the paper. - Selecting the North Direction:
Once the map position has been determined, the orientation of the map must be decided. It is important to select north as the direction for the map. This direction should then be marked on the index map.
5. Drawing Network of Survey Lines
Examining Index Map and Orientation of Paper
The first step in surveying is to examine the index map and the orientation of the paper. This is done to determine the first station point of the survey. From this point, survey lines are drawn out to the scale in their respective directions.
Drawing Survey Lines
After the station point is selected, survey lines are drawn out one by one in their respective directions to the scale. This will help to determine whether the scale and orientation of the paper are appropriate. If necessary, the scale and orientation can be changed and the survey lines can be redrawn.
6. Distributing Closing Error
What is Closing Error in Closed Traverse?
In closed traverse, the last point may not always coincide with the plotted position of the first point. This difference is known as closing error. It is important to note that before adjusting the closing error, it is essential to check that there are no plotting errors.
How Can Closing Error Be Adjusted?
If the closing error is due to field work errors and is reasonably small, it can be adjusted in the office. However, if the error is large, one has to go back to the field and check doubtful measurements. In the office, the closing error can be adjusted by distributing it suitably to all lines graphically or by calculating the corrected coordinates of station points mathematically.
What Happens After Adjusting the Closing Error?
After adjusting the closing error, the network of survey lines is drawn as per the convention.
7. Filling in the Details
Steps of a Land Surveyor
- Understand Survey Lines:
A land surveyor has to go through details of survey lines one by one. This includes noting points of objects in the field and marking them on a drawing sheet with the help of scales. - Identify Objects:
Field books are useful in identifying the objects such as buildings, boundary lines, roads, culvert ends, trees, and electric poles. The measurements for buildings are usually taken near the survey lines and scaled down to fit on the plan. - Join Points:
The points are then joined to mark the object. Standard conventions should be used to show the objects. - Final Touches:
Attending to the field observations of each survey line, all details should be shown on the plan.
8. Colouring the Map
Making Coloured Maps
For the purpose of creating coloured maps, the Indian Standard 962-1989 recommends the use of standard light washes of shades. These shades can be applied to the map to give it a variety of colours and enhance the look of the map. The use of light washes of shades helps to make the map visually appealing, while still maintaining its accuracy and clarity.
9. Drawing Graphical Scale
Why is it necessary to draw a graphical scale?
In order to ensure accuracy when measuring distances between objects on a map, it is necessary to draw a graphical scale of 150 to 270 mm long in the lower right-hand corner of the sheet. This will prevent any inaccuracies due to the potential shrinking of the drawing sheet.
10. Writing Index
What Is a Map Index?
A map index is a set of details that provide information about an area that has been mapped or plotted. This information includes the scale used, the name of the leader of the survey party, and the person who drew the plan or map. It is usually found in the lower right-hand corner of the drawing sheet, and the north direction is indicated at the top right-hand corner.
How Is a Map Index Used?
Map indexes are used to provide additional information regarding a map, such as the scale used, the name of the surveyor, and any other details that may be relevant to the map. This information can help to determine the accuracy of the map and give additional context to its contents.
What Are the Benefits of a Map Index?
Map indexes are an important tool for providing additional information about a map, which can help to clarify what is being represented. It also allows researchers to accurately assess the quality of a map, as well as to identify who was responsible for creating it. Lastly, it is also a great reference for anyone looking to learn more about a particular area.