Instruction Manual for HGC-4 and HGC-6 Geological Compasses

HGC-4 type, HGC-6 type Instruction Manual for the Geological Compass

Product Implementation Standard: Q/HGY06-2020

I. Uses

HGC The primary applications of the geological compass include:

1 , Measurement of structural attitudes: including strike, dip direction, and dip angle;

2 1. Topographic surveying: includes determining orientation (i.e., intersection positioning), measuring slope angle and gradient, and establishing horizontal datum;

3 , Measure the vertical angle.

II. Main Performance

1 , dial: 0 °-360 °, Graduation: 1°. Steering wheel: the outer ring scale indicates slope (the tangent of a 45° slope in both directions), with a graduation of 0.05; the inner ring scale indicates a slope angle of ±90°, in degrees, with a graduation of 1°.

2. The damping time of the magnetic needle (the time it takes for the needle to deflect by 90° and then come to rest in its original position) is less than 15 seconds.

3. Reading error:

a. The angular error between the readings before and after the magnetic needle rotates shall not exceed 0.5°;

b. At 0°–180° and 90°–270°, the error caused by eccentricity in the magnetic needle shall not exceed 0.5°;

c. The reading error of the protractor shall not exceed 0.5°.

4. Spirit level sensitivity:

a. Long spirit level: 15 minutes ±3 ′/2mm

b . Circular level: 30′ ±5 ′/2mm

5. Instrument external dimensions (length × width × height): 80 ×70×35 (mm)

6. Instrument weight: 0.24 kg

III. Principles and Structure

1. Principle: This instrument utilizes a magnetic object—a magnetic needle (which features a special design to shorten the needle’s stabilization time and enhance measurement efficiency)—that is capable of indicating a specific direction along the magnetic meridian. By reading the scale on the graduated ring, the direction of the target relative to the magnetic meridian can be determined. Based on two selected measurement points (or known reference points), the position of another unknown target can be calculated.

2. Structure (refer to the structural schematic diagram) : The instrument consists of an upper cover. 2 With the shell 9 Through the connecting hinge 4 Forms the main body of the instrument. The upper cover houses a reflecting mirror. 3 , which allows the target to be reflected in the mirror. Housing 9 It is equipped with a long front sight on the exterior. 10 , in conjunction with the small sight 1 , capable of aiming at the target. The housing contains a dial. 11 and magnetic needle 8 , the azimuth of the target can be read directly, circular level 13 It can indicate the instrument’s horizontal position. Long spirit level 12 and indicator panel 6 For measuring the slope angle, it can be placed on the steering wheel. 7 Read the inclination angle directly from the scale. Switch 5 It is a magnetic needle braking mechanism. A magnetic declination adjustment shaft is provided on the exterior of the housing. This instrument features a compact structure, small size, and light weight. The instrument housing is manufactured by die-casting and coated with a sand-textured paint on the exterior, offering excellent adhesion, a high-end appearance, corrosion resistance, impact resistance, portability, reliable accuracy, and stable performance. The magnetic needle and spirit level are durable and of superior quality.

IV. Instructions for Use

(1) Measurement of structural attitudes (including strike, dip direction, and dip angle)

1 1. Determining the strike: The strike is the direction of the horizontal projection of the dyke.

Place the instrument's top cover 2 Open the instrument to its full extent, set the local magnetic declination, and place the two long sides of the instrument against a characteristic (representative) surface of the rock layer. Keep the circular bubble level centered, then read the degree indicated by the north pole of the magnetic needle (the end of the copper wire coil serves as the south pole of the magnetic needle); this reading represents the strike of the rock layer.

2 , Measure the dip: the direction perpendicular to the plane indicated by the strike.

Use a connecting hinge. 4 Place the short side of the base or the back of the top cover against the characteristic surface of the rock layer, ensuring that the circular bubble level is centered; the reading indicated by the north pole of the magnetic needle is the dip direction of the rock layer.

3 , Dip angle: the angle between the vertical and the horizontal plane perpendicular to the strike.

Open the top cover 2 When the instrument is positioned at the limit, its side should be perpendicular to the strike and closely aligned with the characteristic plane of the rock layer. Adjust the bubble level until it is centered, then read the degree indicated on the compass dial; this value represents the dip angle of the rock layer.

     In practical measurements, only one of the two factors—strike and dip—needs to be measured, because strike and dip are mutually 90 The relationship of °.

(2) Topographic Surveying (including azimuth determination, slope angle measurement, and horizontal line identification)

1 1. Determining the azimuth: the direction and location of the target. Azimuth determination is also known as intersection positioning.

（ 1 ) Measurement method when the target is above the line of sight (horizontal line).

Hold the instrument firmly in your right hand, with the back of the upper cover facing the observer and your arm close to your body to minimize shaking. Use your left hand to adjust the long sighting tube and the reflecting mirror, then turn your body until the image of the target and the tip of the long sighting tube are simultaneously reflected in the mirror and bisected by the mirror’s center line. Keep the circular bubble level centered, and the reading indicated by the north pole of the magnetic needle is the direction to the target.

Using the same method, measure the target at another measurement point. By taking measurements of the same target from two points and drawing two lines along the measured angles that intersect at the target, the target’s position can be determined.

（ 2 ) Measurement method when the target is below the line of sight (horizontal line).

Hold the instrument firmly in your right hand, with the reflecting mirror positioned opposite the observer; keep your arm close to your body to minimize shaking. With your left hand, adjust the long sighting tube and the upper cover, then turn your body until the target and the tip of the sighting notch are simultaneously aligned within the elliptical aperture of the reflecting mirror and bisected by the mirror’s line of sight. Keep the circular bubble level centered, and read the degree indicated by the south pole of the magnetic needle—this is the direction to the target.

Using the same method, measure the target from another measurement point. By taking measurements from two points and determining the two lines that intersect at the measured angles, the position of the target can be established.

2 , Slope angle: the angle between the line of sight to the target and the horizontal plane.

Hold the instrument’s housing and base with your right hand, with the long sighting tube on the observer’s side. Position the instrument so that its plane is perpendicular to the horizontal, with the long bubble level centered at the bottom. With your left hand, adjust the top cover and the long sighting tube until the target and the aperture of the sighting tip are both bisected by the elliptical line etched on the reflecting mirror. Then, use the middle finger of your right hand to adjust the handle, observing through the reflecting mirror to ensure that the long bubble level is centered. The reading indicated on the dial mounted on the handle at this moment represents the slope angle of the target.

To measure the dip angle of a slope, simply open the top cover to its full extent, place the instrument’s side directly against the slope, adjust the long bubble level to center, and read the angle—this will be the dip angle of the slope (which is identical to the dip angle in structural-geological measurements).

When measuring the slope angle or gradient using the two methods described above, the value indicated by the dial on the outer scale of the steering wheel represents the gradient, which is the tangent of the slope angle; for example, if the reading is 20 , which indicates a slope of 0.2 º; The value indicated by the indicator dial on the inner scale is the slope angle, in degrees; for example, if the reading is 20 , which means the slope angle is 20 °.

3 1. Establish the horizontal line:

Tilt the long-range sight so that it lies in the same plane as the box surface, and then tilt the top cover to 45 °, with the sighting point vertical and parallel to the upper cover, align the indicator with “ 0 “Adjust the instrument so that the long bubble is centered; then the line of sight passing through the sighting aperture at the sighting tip and the elliptical aperture of the reflecting mirror will coincide with the horizontal line.”

(3) Measuring the Vertical Angle of an Object

Rotate the top cover to its extreme position, then press the side of the instrument firmly against a representative flat surface of the object (such as a drill pipe). Adjust the bubble level until it is centered; the reading indicated by the dial at this point represents the vertical angle of the object.

(4) Magnetic Declination Adjustment

Magnetic declination is classified as either east or west and is measured and published by the national surveying authority. To adjust for magnetic declination, first align the compass needle with any whole-degree mark on the compass dial, keep the instrument stationary, and then rotate the dial until the angle of rotation relative to the needle exactly matches the local magnetic declination. If the declination is west, turn the dial counterclockwise; if it is east, turn the dial clockwise.

V. Precautions

1 The magnetic needle, the jewel bearing, and the agate bearing are the instrument’s principal components and must be carefully protected and kept clean to avoid compromising the magnetic needle’s sensitivity. When the instrument is not in use, it should be Lock it up . After the instrument is turned off, via the switch and the lever action Automatically lift the magnetic needle to disengage the pusher from the agate bearing, thereby preventing wear on the pusher.

2 , The varying magnetic dip angles across the globe cause the magnetic needle to tilt, necessitating adjustments to the magnetic needle's N extreme or S A highly balanced suspension wire (made of non-magnetic material) is used to keep the magnetic needle level; by adjusting the number of turns or the position of the suspension wire, the needle can remain horizontal regardless of the region.

3 Do not disassemble any hinges lightly, as this may cause them to loosen and compromise accuracy.

4 Avoid exposing the instrument to high temperatures for extended periods to prevent air leakage and malfunction of the water bladder.

5 The pivoting parts of the hinge should be regularly lubricated with watch oil to prevent dry friction and breakage.

6 The instrument should be placed in a well-ventilated, dry location, away from magnetic objects.

7 , Full-unit product warranty 12 Months; damage caused by human error or external forces is not covered under the warranty.

The data in the table are based on the latest International Geomagnetic Reference Model.

, time node: December 31, 2017

Harbin Optical Instruments Factory Co., Ltd.

HARBIN OPTICAL INSTRUMENT FACTORY LTD.

ground   Address: Jingwei Third Road, Daoli District, Harbin City 32 Number

Post   Editor: 150010

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E-mail： hopt@hopt.cn