- History of Prismatic Compass Survey
- Components of Prismatic Compass Survey
- Working Principle of Prismatic Compass Survey
- Types of Prismatic Compass Survey
- Field Procedure for Prismatic Compass Survey
- Recording and Plotting Bearings of Prismatic Compass Survey
- Sources of Errors in Prismatic Compass Survey
- Methods to Reduce Errors in Prismatic Compass Survey
- Frequently Asked Question (FAQs)
History of Prismatic Compass Survey
Ancient Origins: The use of magnetic compasses dates back to ancient China, across the 4th century BC, where they have been to start with hired for navigation and divination.
European Adoption: By the 12th century, magnetic compasses had made their manner to Europe, turning into critical gear for maritime navigation in the course of the Age of Exploration.
Introduction of Surveying: In the sixteenth century, the concepts of compass surveying started out to take form as land surveying received significance in Europe for assets delineation and useful resource management.
Development of the Magnetic Compass: Early compasses have been rudimentary and regularly inaccurate; upgrades in substances and layout caused the introduction of greater dependable magnetic compasses.
Invention of the Prismatic Compass: The prismatic compass became invented withinside the nineteenth century, improving the conventional compass with a prism that allowed for clearer sighting and greater correct readings.
Standardization of Design: By the late 1800s, the layout of the prismatic compass became standardized, making it simpler for surveyors to undertake and use withinside the field.
Influence of Surveying Schools: The status quo of surveying faculties and expert groups withinside the nineteenth century helped popularize the usage of the prismatic compass amongst aspiring surveyors.
Integration with Advanced Techniques: Throughout the 20th century, the prismatic compass have become a foundational device along with different surveying strategies like triangulation and leveling.
Resilience withinside the Digital Era: Despite the arrival of digital devices and GPS technology, the prismatic compass stays applicable because of its simplicity, portability, and effectiveness in diverse environments.
Components of Prismatic Compass Survey
Compass Box: The main housing of the compass that holds all other components together and affords a strong platform for correct readings.
Magnetic Needle: A lightweight magnetized needle that aligns itself with the Earth`s magnetic discipline, indicating magnetic north.
Graduated Circle: A round scale, typically marked in degrees, that permits surveyors to examine the perspective or bearing being measured relative to magnetic north.
Prism: A glass prism located above the compass needle, which permits the observer to view the analyzing of the graduated circle genuinely whilst sighting an object.
Sighting Vanes: Two adjustable arms or vanes that resource in appropriately sighting a target object. One vane is typically fixed, whilst the alternative is movable for specific alignment.
Leveling Device: A bubble stage connected to the compass field to make certain that the device is stage earlier than taking measurements, which complements accuracy.
Clamp and Tangent Screw: A mechanism that allows the compass to be locked in role and fine-tuned for specific changes all through measurement.
Focusing Lens: Some fashions encompass a lens that enables the surveyor cognizance on remote objects, enhancing the readability of sighting and decreasing parallax errors.
Compass Cover: A protective cover that shields the compass from environmental factors and stops harm all through transportation.
Field Book: While now no longer a bodily a part of the compass itself, a discipline ee-e book is crucial for recording measurements and observations taken all through the survey, making sure correct facts series and analysis.
Working Principle of Prismatic Compass Survey
Magnetic Orientation: The prismatic compass operates primarily based totally at the precept that a magnetic needle aligns itself with the Earth`s magnetic discipline, pointing closer to magnetic north.
Placement of the Compass: The compass is located on a stable, stage surface, making sure that it isn’t motivated via way of means of close by magnetic gadgets that may have an effect on the accuracy of the readings.
Sighting the Target: The surveyor makes use of the sighting vanes to align the compass with the goal item. The constant vane facilitates function the compass, whilst the movable vane aids in specific alignment.
Reflection through the Prism: The mild from the goal item passes via the prism, which displays the photograph to the surveyor`s eye, taking into account correct sighting whilst analyzing the compass scale.
Reading the Graduated Circle: As the surveyor aligns the sighting vanes with the goal, they have a look at the placement of the magnetic needle towards the graduated circle, which presentations the attitude or bearing relative to magnetic north.
Taking the Measurement: The attitude study from the graduated circle represents the magnetic bearing of the road from the tool to the goal item.
Magnetic Declination Adjustment: If necessary, the surveyor can also additionally regulate the analyzing to account for the distinction among magnetic north and authentic north (magnetic declination), making sure greater correct positioning.
Recording the Bearing: The measured bearing is recorded in a discipline ee-e book along side different applicable records including distance and different angles, that’s essential for in addition calculations and mapping.
Repeatability: To beautify accuracy, surveyors can also additionally take more than one readings from extraordinary places or repeat measurements from the identical point, averaging the consequences if necessary.
Types of Prismatic Compass Survey
| Type of Survey | Description | Key Features |
|---|---|---|
| 1. Traversing Method | A method of surveying where a series of connected lines are measured in succession. | – Measures angles and distances between points |
| – Can be either open or closed traverse | ||
| – Used for mapping and property boundary delineation | ||
| 2. Open Traverse | A type of traversing method that does not return to the starting point. | – Forms a linear path without closing the loop |
| – Useful for long-distance surveys | ||
| – Requires additional data for accuracy | ||
| 3. Closed Traverse | A method where the survey starts and ends at the same point, creating a closed loop. | – Helps check for errors in measurements |
| – Ensures that the sum of angles equals the expected total | ||
| – Often used for boundary surveys | ||
| 4. Radial Survey | Involves taking bearings and measurements from a central point to various surrounding points. | – Useful for mapping circular areas or features |
| – Allows for efficient data collection | ||
| 5. Level Survey | Focuses on determining the elevations of various points relative to a baseline. | – Combines compass bearings with leveling instruments |
| – Essential for construction and drainage projects | ||
| 6. Reconnaissance Survey | A preliminary survey to assess an area before detailed surveying work is conducted. | – Aims to gather initial data and identify key features |
| – Helps in planning the detailed surveying approach | ||
| 7. Preliminary Survey | Conducted to collect baseline data for further detailed studies. | – Involves measuring angles and distances |
| – Forms the groundwork for comprehensive surveys | ||
| 8. Control Survey | A detailed survey that establishes control points for further measurements and surveys. | – Provides a framework for other surveying techniques |
| – Ensures the accuracy and reliability of results |
Field Procedure for Prismatic Compass Survey
Preparation: Before heading to the field, collect all important equipment, which include the prismatic compass, discipline book, measuring tape, and any extra gear required for the survey.
Site Selection: Choose a suitable location for the survey that offers a clean line of sight to the goal objects. Ensure the vicinity is unfastened from magnetic interference, which includes massive metal structures.
Setting Up the Compass: Place the prismatic compass on a stable, stage surface. Use the leveling device (bubble level) to make sure that the compass is flawlessly horizontal for correct readings.
Finding Magnetic North: Allow the magnetic needle to settle. Note the placement of the needle whilst it factors in the direction of magnetic north, which serves as a reference for all subsequent measurements.
Sighting the First Point: Use the sighting vanes to intention at the primary goal point. Align the constant vane with the goal and alter the movable vane till it traces up flawlessly.
Taking Measurements: Read the perspective or bearing indicated through the magnetic needle in opposition to the graduated circle. Record the bearing withinside the discipline book, noting the corresponding goal object.
Measuring Distance: If required, use a measuring tape to decide the space to the goal point. Record this records along the bearing withinside the discipline book.
Repeating for Additional Points: Move to the subsequent goal point, re-organising the compass position, and repeat the sighting and size method for every goal object.
Error Checking: After finishing measurements for all factors, behavior assessments through measuring again to formerly hooked up factors. This facilitates perceive any mistakes in readings.
Recording and Plotting Bearings of Prismatic Compass Survey
Field Book Preparation: Use a well-organized area book with columns categorised for the factor variety, bearings, distances, and any extra notes required for clarity.
Consistent Notation: Establish a clear notation machine for recording bearings (e.g., the usage of degrees, minutes, and seconds or decimal degrees). Consistency is important for correct plotting.
Recording Bearings: As you take every bearing with the prismatic compass, immediately report it withinside the area ee-e book. Include the corresponding factor call or variety for clean reference.
Noting Distances: Along with the bearings, report the gap to every goal factor. This information is crucial for accurate plotting and subsequent calculations.
Including Additional Observations: Make notes of any significant observations or situations that may have an effect on the survey, together with weather, terrain, or magnetic interference.
Converting Bearings to Azimuths: If necessary, convert recorded bearings to azimuths (a complete 360-degree system) for plotting. For example, North (0°) may be recorded as 0°, East as 90°, South as 180°, and West as 270°.
Drawing the Base Line: On graph paper or a plotting software, draw a baseline (reference line) that represents a known direction, typically magnetic north or true north, at the bottom of the plot.
Plotting Points: Using a protractor, degree the recorded bearings from the baseline to devise every factor as it should be at the graph. Ensure to degree angles successfully to keep the integrity of the survey information.
Measuring Distances: Use the size of the graph to degree and plot the distances similar to every bearing as it should be. This step includes changing the gap from the sphere book to the plotting scale used at the graph.
Sources of Errors in Prismatic Compass Survey
Instrumental Errors: Inaccuracies springing up from the prismatic compass itself, consisting of misalignment of the magnetic needle, defects withinside the prism, or tired graduations at the compass box.
Magnetic Declination: The distinction among magnetic north and genuine north can result in mistakes if now no longer accounted for, affecting the accuracy of the bearings recorded for the duration of the survey.
Local Magnetic Interference: Nearby steel objects, magnetic fields, or electric installations can distort the magnetic field, inflicting the compass needle to deviate from genuine magnetic north.
Parallax Error: This happens while the surveyor does now no longer align their line of sight efficaciously with the analyzing at the graduated circle, main to faulty perspective measurements.
Improper Leveling: If the compass isn’t always flawlessly degree while taking measurements, it is able to motive full-size mistakes withinside the readings. A bubble degree ought to continually be used to test for leveling.
Human Error: Mistakes made through the surveyor, including misreading the compass scale, wrong recording of data, or misalignment of sighting vanes, can result in inaccuracies in measurements.
Environmental Conditions: Factors including temperature, humidity, and atmospheric strain can have an effect on the overall performance of the compass and the steadiness of the magnetic needle.
Inconsistent Sighting: Failing to continuously use the equal method for sighting can introduce variability withinside the measurements. It`s critical to preserve a standardized method.
Geometric Errors: Errors can rise up from wrong triangulation or plotting methods, consisting of the miscalculation of angles and distances for the duration of the plotting process.
End-Point Errors: Errors can arise while measuring distances among points, particularly if the measuring tape isn’t always held taut or if the terrain is uneven, main to discrepancies withinside the plotted positions.
Methods to Reduce Errors in Prismatic Compass Survey
Regular Calibration: Ensure the prismatic compass is regularly calibrated and serviced to hold accuracy. Check for any defects or put on and tear earlier than every survey.
Magnetic Declination Adjustment: Always account for magnetic declination via way of means of adjusting readings to transform magnetic bearings to genuine bearings, the use of nearby declination values acquired from dependable reassets.
Avoid Magnetic Interference: Conduct surveys farfar from big metal structures, electric equipment, or any magnetic reassets that could intervene with the compass needle.
Leveling the Compass: Use the built-in leveling tool to make certain the compass is perfectly stage earlier than taking measurements. This is important for acquiring correct perspective readings.
Consistent Sighting Technique: Maintain a standardized technique for sighting and aligning the goal objects. Practice top behavior to lessen the probabilities of parallax mistakes.
Multiple Readings: Take a couple of readings for every bearing and distance, then common them to reduce the effect of random mistakes and enhance ordinary accuracy.
Environmental Considerations: Be aware of environmental situations along with wind and sunlight, that could have an effect on visibility and stability. Choose calm, clean days for surveying every time possible.
Thorough Training: Ensure that every one employees worried withinside the surveying manner are well-trained and acquainted with the operation of the prismatic compass, in addition to blunders detection and correction techniques.
Careful Data Recording: Immediately document measurements withinside the area ee-e book to reduce the chance of forgetting or misinterpreting facts. Double-test entries for accuracy.
Error Analysis and Adjustment: After completing the survey, conduct a thorough blunders analysis via way of means of evaluating the outcomes with acknowledged benchmarks or manipulate points. Make vital changes to the recorded facts earlier than finalizing the survey outcomes.
Freqently Asked Questions (FAQs)
1. What is a prismatic compass?
A prismatic compass is a surveying device used to degree horizontal angles and bearings with excessive accuracy, using a magnetic needle and a prism for sighting.
2. How does a prismatic compass work?
It works by aligning the magnetic needle with magnetic north even as the surveyor attractions a goal via a prism, making an allowance for correct studying of angles towards a graduated scale.
3. What are the main components of a prismatic compass?
Key additives encompass the magnetic needle, compass box, prism, sighting vanes, and graduated circle for studying angles.
4. What forms of surveys may be conducted the use of a prismatic compass?
It is usually utilized in traversing, leveling, reconnaissance surveys, and boundary surveys.
5. How do you record bearings in a prismatic compass survey?
Bearings are recorded in a area ee-e book together with corresponding distances and any applicable observations, the use of a constant notation system.
