- Principle of Prismatic Compass
- Components of a Prismatic Compass
- Types of Prismatic Compasses
- Specifications of a Prismatic Compass
- Prismatic Compass Survey
- Prismatic Compass Parts
- Errors in Compass Surveying
- Difference Between the Prismatic Compass and Surveyor Compass
- Frequently Asked Question (FAQs)
Principle of Prismatic Compass
The working of a prismatic compass is primarily based totally at the precept of magnetic bearings and the alignment of the magnetic needle with the Earth`s magnetic field. Below are 10 easy factors explaining its precept:
Magnetic Needle Alignment
The magnetic needle in the compass aligns itself with the Earth`s magnetic field, pointing toward the magnetic north.
Graduated Circle
The compass has a round scale graduated in degrees, permitting unique dimension of angles and bearings.
Sighting Mechanism
The prism and sighting vane assist in as it should be sighting gadgets and analyzing the bearing simultaneously.
Prism Functionality
The prism magnifies the graduated scale, allowing the consumer to examine values with readability and precision.
Pivoted Magnetic Needle
The needle is pivoted on the center, permitting it to transport freely and align with the magnetic meridian.
Line of Sight
The compass measures the attitude among the road of sight to an item and the magnetic meridian.
Magnetic Bearings
Bearings are measured in degrees, with 0° pointing to the magnetic north and 360° finishing the circle.
Relative Directions
The compass permits measurements relative to each the magnetic north and a designated reference direction.
Friction-Free Movement
The magnetic needle is housed in a friction-unfastened casing to make sure easy and correct movement.
Use of Damping
Some prismatic compasses use damping to lessen needle oscillation, stabilizing it fast for readings.
Components of a Prismatic Compass
The working of a prismatic compass is primarily based totally at the precept of magnetic bearings and the alignment of the magnetic needle with the Earth`s magnetic field. Below are 10 easy factors explaining its precept:
Magnetic Needle Alignment
The magnetic needle in the compass aligns itself with the Earth`s magnetic field, pointing toward the magnetic north.
Graduated Circle
The compass has a round scale graduated in degrees, permitting unique dimension of angles and bearings.
Sighting Mechanism
The prism and sighting vane assist in as it should be sighting gadgets and analyzing the bearing simultaneously.
Prism Functionality
The prism magnifies the graduated scale, allowing the consumer to examine values with readability and precision.
Pivoted Magnetic Needle
The needle is pivoted on the center, permitting it to transport freely and align with the magnetic meridian.
Line of Sight
The compass measures the attitude among the road of sight to an item and the magnetic meridian.
Magnetic Bearings
Bearings are measured in degrees, with 0° pointing to the magnetic north and 360° completing the circle.
Relative Directions
The compass allows measurements relative to each the magnetic north and a designated reference direction.
Friction-Free Movement
The magnetic needle is housed in a friction-unfastened casing to make sure easy and correct movement.
Use of Damping
Some prismatic compasses use damping to lessen needle oscillation, stabilizing it fast for readings.
Types of Prismatic Compasses
| Type | Description | Applications |
|---|---|---|
| Dry Prismatic Compass | The magnetic needle moves freely in a dry environment without liquid damping. | Used in standard surveying and navigation tasks. |
| Liquid Prismatic Compass | The magnetic needle is immersed in a damping liquid, reducing oscillations for faster stabilization. | Ideal for use in windy or unstable conditions. |
| Military Prismatic Compass | A rugged and durable compass designed for military use, often equipped with night vision features. | Used for tactical navigation and field operations. |
| Engineer’s Prismatic Compass | A larger and more precise version, often used for professional engineering surveys. | Suitable for detailed topographical and civil engineering work. |
| Mirror Prismatic Compass | Equipped with an additional mirror for enhanced accuracy in sighting and reading. | Used in advanced surveying and triangulation tasks. |
| Global Prismatic Compass | Designed to function accurately in both the northern and southern hemispheres. | Ideal for international travel and navigation. |
Specifications of a Prismatic Compass
Graduated Circle
The graduated circle is marked in tiers from 0° to 360°, enabling precise measurement of bearings. It is generally fabricated from aluminum or brass to make certain sturdiness and accuracy.
Magnetic Needle
The magnetic needle is light-weight and quite touchy, crafted from magnetized metal or alloy. It is balanced to reduce mistakes as a result of nearby attraction.
Size and Dimensions
A standard prismatic compass generally has a diameter starting from seventy five mm to a hundred mm, making it compact and transportable for subject use.
Material Construction
The compass is fabricated from corrosion-resistant substances like brass or aluminum alloy, making sure sturdiness in harsh environmental conditions.
Prism Magnification
The prism magnifies the graduated scale, permitting clean and correct readings even for minute measurements.
Accuracy and Sensitivity
The compass gives an accuracy stage of ±0.5° to ±1°, relying at the first-rate and form of the instrument. It is quite touchy to adjustments in magnetic direction.
Damping Mechanism
Some prismatic compasses consist of a damping liquid or mechanism to lessen oscillations of the magnetic needle, supplying faster stabilization.
Weight
Lightweight designs, generally among a hundred and fifty to 250 grams, make certain ease of use and portability with out compromising on functionality.
Protective Features
Equipped with a tumbler cowl to shield the needle and graduated circle, and a locking mechanism to steady the needle whilst now no longer in use.
Operational Range
The compass operates successfully inside a temperature variety of -10°C to 50°C, making it appropriate for various climatic conditions.
Prismatic Compass Survey
1. Purpose of Prismatic Compass Survey
To measure horizontal angles and bearings of lines.
To establish the direction and orientation of diverse survey lines.
2. Equipment Used
Prismatic Compass: The number one tool for measuring bearings.
Tripod: Used to stabilize the compass for the duration of measurements.
Ranging Rods: To mark factors withinside the subject.
Field Book: To report observations and bearings.
3. Surveying Procedure
Setup: Mount the prismatic compass on a tripod and stage it the use of the adjustable screws.
Orientation: Align the compass to the magnetic north the use of the magnetic needle.
Sighting: Use the sighting vane to consciousness at the item or point.
Reading Bearings: Read the bearing at the graduated circle thru the prism.
Recording Data: Note the bearings and different information withinside the subject book.
4. Types of Bearings Measured
Whole Circle Bearing (WCB): Bearings measured clockwise from the magnetic north (0° to 360°).
Reduced Bearing (RB): Bearings measured inside a quadrant (N-S, E-W).
5. Applications of Prismatic Compass Survey
Topographical Surveys: Mapping herbal and man-made features.
Route Surveys: Determining alignments for roads, pipelines, and canals.
Boundary Surveys: Establishing belongings limitations and demarcations.
6. Advantages of Prismatic Compass Survey
Portable and clean to apply withinside the subject.
Provides brief measurements of bearings.
Suitable for hard terrain and remote locations.
7. Limitations of Prismatic Compass Survey
Affected by magnetic interferences from close by items.
Accuracy decreases in areas with excessive magnetic anomalies.
8. Precautions During Survey
Avoid using the compass close to steel items or electric equipment.
Ensure the compass is stage and stabilized for the duration of measurements.
Recheck readings to decrease errors.
Prismatic compass surveys are a essential method in surveying, imparting a stability of simplicity and performance for small-scale projects. Proper coping with and know-how of the tool make sure dependable and correct results.
Prismatic Compass Parts
1. Magnetic Needle
Function: The magnetic needle is the number one thing that aligns with the Earth`s magnetic field, indicating the course of magnetic north. It is hooked up on a pivot factor and is unfastened to rotate.
Material: Typically fabricated from magnetized metal or alloy.
2. Graduated Circle
Function: This is a round scale marked in stages from 0° to 360°, used to degree bearings and angles.
Material: Usually crafted from long lasting metals like aluminum or brass for accuracy and longevity.
3. Prism
Function: The prism magnifies the graduated circle and lets in the consumer to peer the bearing studying thru an immediate line of sight. It facilitates in studying the bearing with out parallax errors.
Material: Typically fabricated from clean glass or optical substances for precision.
4. Sighting Vane
Function: A vertical slit or cord used to align the tool with the item being sighted. The sighting vane facilitates in directing the compass to the goal.
Material: Often fabricated from metallic or skinny cord.
5. Base Plate
Function: The flat floor on which the compass additives are hooked up. It gives balance to the compass in the course of use.
Material: Usually fabricated from metallic or plastic for durability.
6. Pivot Point
Function: A significant factor round which the magnetic needle pivots. This lets in the needle to rotate freely and align with the Earth`s magnetic field.
Material: Often fabricated from a metallic or top notch bearing fabric to lessen friction.
7. Glass Cover
Function: Protects the magnetic needle, graduated circle, and prism from dust, dirt, and bodily damage.
Material: Made of clean, long lasting glass.
8. Lifting Pin and Brake
Function: A mechanism that lifts the magnetic needle off the pivot factor to save you it from transferring in the course of shipping or storage. It additionally locks the needle in region whilst now no longer in use.
Material: Typically fabricated from metallic.
9. Mirror
Function: A small replicate connected to the lid of the compass, used for sighting the goal and aligning the compass with the item accurately.
Material: Usually fabricated from glass with a reflective coating.
10. Adjustable Screw
Function: A screw that lets in the compass to be adjusted and leveled, making sure correct readings whilst the tool is located on choppy surfaces.
Material: Typically fabricated from metallic for electricity and durability.
11. Circular Ring
Function: A ring connected to the compass for smooth coping with and portability, regularly used to keep the compass securely at the same time as taking readings.
Material: Made of metallic or plastic for light-weight use.
12. Damping Mechanism
Function: Some prismatic compasses encompass a damping machine, which facilitates stabilize the magnetic needle fast through decreasing oscillations.
Material: Can be a liquid or mechanical damping machine relying at the compass type.
Errors in Compass Surveying
1. Magnetic Declination Error
Cause: Magnetic declination refers back to the attitude among magnetic north (the route the compass needle points) and actual north (geographical north). This mistakess happens if the compass is utilized in regions with large magnetic declination, inflicting wrong bearings.
Correction: The magnetic declination should be accounted for through making use of the nearby version of magnetic north.
2. Local Magnetic Interference
Cause: Objects like metallic structures, vehicles, or electric system can distort the Earth`s magnetic field, inflicting the compass needle to factor withinside the incorrect route.
Correction: Ensure the compass is saved farfar from any steel or magnetic gadgets throughout measurement.
3. Instrumental Error
Cause: The compass itself might also additionally have imperfections, which includes misalignment of the needle, defects withinside the graduated circle, or harm to the prism, main to faulty readings.
Correction: Regular calibration and renovation of the compass can assist lessen instrumental errors.
4. Personal Error
Cause: Errors as a result of the surveyor`s coping with of the compass, which includes parallax in analyzing the graduated scale or wrong sighting of the target.
Correction: Careful coping with, right sighting techniques, and making sure the compass is held stage can decrease private errors.
5. Collimation Error
Cause: This error happens whilst the road of sight of the device does now no longer coincide with the axis of the magnetic needle. It consequences in moderate deviations withinside the bearing readings.
Correction: Regular assessments and modifications of the compass to make sure the sighting vane is aligned nicely with the needle.
6. Wrong Alignment of Compass
Cause: Improper leveling of the compass can result in faulty readings. If the compass isn’t aligned with the horizontal plane, the needle won’t factor correctly.
Correction: Always stage the compass the usage of the adjustable screws and take a look at the alignment earlier than taking measurements.
7. Errors Due to Wind or Vibration
Cause: Wind or vibrations withinside the environment can reason the needle to oscillate, main to faulty readings.
Correction: Using a damping mechanism withinside the compass or making sure a solid surroundings can decrease those errors.
8. Refraction Error
Cause: The environment can reason moderate refraction of light, affecting the sighting thru the prism and main to wrong bearings.
Correction: This mistakess is commonly negligible however may be minimized through carrying out surveys in solid climate conditions.
Difference Between the Prismatic Compass and Surveyor Compass
| Prismatic Compass | Surveyor Compass |
| Graduation circle is fixed to a broad type needle. Hence, it will not rotate with the line of sight. | Graduation circle is fixed to the box. Hence, it rotates with the line of sight. |
| There is a prism at the viewing end. | At the viewing end, there is no prism. There is only a slit. |
| Sighting and reading can be done simultaneously | Sighting and viewing cannot be done simultaneously. |
| The magnetic needle does not act as an index. | Magnetic needle acts as index while reading. |
| The graduations are in whole circle bearing. | The graduations are in the quadrantal system or called Reduced Bearing. |
| Graduations are marked inverted since their reflection is read through prism. | Graduations are marked directly. They are not inverted. |
| The reading is taken through a prism. | The reading is taken by directly viewing from the top glass. |
| Tripods may or may not be used. It can be held on a stretched hand also. | Tripod is essential for using it. |
Freqently Asked Questions (FAQs)
1. What is meant by prismatic compass?
2. Why prism is used in prismatic compass?
3. What is the distinction among a prismatic compass and a magnetic compass?
A prismatic compass has a prism for magnifying and appropriately studying bearings, at the same time as a magnetic compass simplest affords route with a magnetic needle.
4. What types of errors can arise in compass surveying?
Common mistakes encompass magnetic declination error, neighborhood magnetic interference, private error, and collimation error.
5. What is magnetic declination?
Magnetic declination is the perspective among magnetic north and real north, which varies through region and have to be taken into consideration whilst the usage of a prismatic compass.
