Instruction Manual for HGC-1 and HGC-2 Geological Compasses

HGC-1 type, HGC-2 type Instruction Manual for the Geological Compass

Product Implementation Standard: Q/HGY06-2020

I. Purpose >>

The primary applications of the HGC geological compass include:

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

2. Topographic surveying: includes determining orientation (i.e., intersection positioning), measuring slope angles, and establishing horizontal levels;

3. Measure the vertical angle.

II. Main Performance >>

1. 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 30–60 seconds.

2 Reading error: a. The difference between the degree 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°.

3. Level sensitivity: a. Long level: 15′ ± 3′ per 2 mm

b. Circular level: 30′±5′/2mm

4. Instrument external dimensions (length × width × height): 85 × 73 × 35 mm (HGC-1 model), 73 × 73 × 35 mm (HGC-2 model).

5. Instrument weight: 0.26 kg (HGC-1 model), 0.20 kg (HGC-2 model)

III. Principles and Structure >>

1 Principle: This instrument exploits the property of magnetic objects (i.e., a magnetic needle) to align themselves in a specific direction along the magnetic meridian. By reading the scale on the graduated ring, the direction of a 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 schematic diagram): The instrument consists of an upper cover 6 and a housing 13 joined by a hinge 8, forming the main body of the instrument. The upper cover houses a reflecting mirror 7, which enables the target to be reflected in the mirror. On the exterior of the housing 13 is mounted a long sighting device 1; in conjunction with the small sighting device 5, it allows for accurate aiming at the target. Inside the housing are a graduated dial 2 and a magnetic needle 3, enabling direct reading of the target’s azimuth. A circular level 10 indicates the instrument’s horizontal position. A long spirit level 4 and an indicator dial 11 are provided for measuring slope angles, with readings taken directly from the inclination scale on the adjustment knob 12. Switch 9 serves as the magnetic needle braking mechanism. An adjustment shaft for magnetic declination is located on the outer side of the housing. This instrument features a compact structure, small size, and light weight; its housing is manufactured by die-casting and coated with wrinkle-textured paint, providing resistance to peeling, corrosion, and impact, while also ensuring portability, reliable accuracy, and stable performance. The instrument’s magnetic needle and spirit levels are durable and of high quality.

1 Long sighting telescope 2 Graduated dial 3 Magnetic needle 4 Long spirit level 5 Small sighting telescope 6 Top cover 7 Reflecting mirror 8 Connecting hinge 9 Switch 10 Circular spirit level 11 Indicator dial 12 Steering wheel 13 Housing

IV. Instructions for Use >>

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

1. Determining the strike: The strike is the direction of the rock vein’s horizontal projection.

Open the instrument’s top cover 6 to its full extent, set the local magnetic declination, and then place the instrument’s two long sides against a characteristic (representative) surface of the rock layer. Keep the circular bubble level centered, and read the value indicated by the north pole of the magnetic needle (note that the end wrapped with copper wire is the south pole of the needle); this reading represents the strike of the rock layer.

2. Dip direction: the direction perpendicular to the plane indicated by the strike.

Place the short side of the base plate beneath the connecting hinge 8, or the back of the top cover, against the characteristic surface of the rock layer, ensuring that the circular spirit level remains centered. The reading indicated by the north pole of the magnetic needle at this point represents 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 6 to its limit position, ensuring that the instrument’s side is perpendicular to the strike and tightly aligned with the characteristic surface of the rock layer. Adjust the bubble level until it is centered, then read the degree indicated on the dial; this value represents the dip angle of the rock layer.

In practical measurements, it is sufficient to determine only one of the two factors—strike or dip—since strike and dip are perpendicular to each other, differing by 90°.

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

1. Determining Position: The direction and location of the target; this process 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 line of sight. Keep the circular bubble level centered, and read the degree indicated by the north pole of the magnetic needle—this 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 different points, the two lines corresponding to the measured angles will intersect at the target, thereby determining its position.

(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 measuring the target from two points and determining the intersection of the two lines at the measured angles, the target’s position can be established.

2. Slope angle: the angle between the line of sight from the observer 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 slope’s dip angle (which is identical to the dip angle in structural analysis).

3. Establish the horizontal line

Turn the long collimator until it lies in the same plane as the box face, tilt the top cover to 45°, and ensure that the collimation point is vertically parallel to the top cover. Align the indicator with “0”, then adjust the instrument so that the long bubble is centered. At this point, the line of sight passing through the eyepiece on the collimation point 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. When adjusting for magnetic declination, first align the compass needle with any whole-degree mark on the scale, keep the instrument stationary, and then rotate the graduated dial until the angle of rotation relative to the needle exactly equals 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 The action of the lever 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 magnetic needles 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 and direct sunlight to prevent air leakage and malfunction.

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

Electricity   Words: 400-030-0319         0451-84286338      

network   Address: www.hrboptical.com           

E-mail： hopt@hopt.cn