Instruction Manual for the DQL-10A Altimeter Compass

DQL-10A Instruction Manual for the Type Altimeter Compass

The DOL-10A altimeter compass combines two functions—slope/altitude measurement and azimuth determination. It consists of a liquid-damped compass and an inclinometer, offering convenient operation. Its robust aluminum housing is impact-resistant, waterproof, and corrosion-proof. This high-quality, high-precision instrument delivers fast, accurate measurements and can be operated with one hand.

The protractor is calibrated in degrees and percentages (0–90°, 0–150%), with graduations spaced at 1°/1%, enabling convenient measurements in both horizontal and vertical directions. The compass is calibrated in azimuths (0–360°).

Feature Overview

Optical adjustment

Optically adjust the eyepieces by rotating them with your fingers until the scale lines are sharply focused; ensure that the eyepiece slit at the azimuth compass remains vertical and that the eyepiece slit at the protractor remains horizontal.

Direction compass

Structure

This compass features a precision design that ensures quick and easy operation. Its dial is supported by jewel bearings and equipped with liquid damping, allowing for smooth, vibration-free rotation.

Operation

With both eyes open, look through the eyepiece on one side of the compass and align the index line with the target. The main scale (large numerals) indicates your azimuth relative to the target, while the smaller numerals indicate the azimuth in the opposite direction—i.e., the target’s azimuth relative to you. This makes it easier to calculate an accurate azimuth.

Because viewing with only one eye can lead to latent strabismus, which may affect the accuracy of some individuals’ readings, we recommend using both eyes.

Please verify whether you have latent strabismus using the following method: Look with both eyes, then close one eye (keeping the eye that is facing the eyepiece open). If there is no difference between the two views, this confirms that the axes of the two eyes are aligned, and you may then use just one eye. If there is a difference, close the other eye and adjust your gaze so that you can still see part of the instrument; at this point, you should observe the reticle positioned above the instrument and directly aligned with the target.

This instrument can also be used for triangulation, as shown in Figure 2. Suppose that, according to the primary scale, the bearing to the small hill is 0° and the bearing to the road bend is 64°; alternatively, viewed from the opposite scale, these bearings are 180° and 244°. Your position is the intersection of these two lines. If magnetic declination is taken into account, the result will be even more accurate.

The cotangent table on the back of this instrument can be used to calculate distance, particularly for determining position when two landmarks separated by a small angle are visible. The calculation procedure is illustrated in Figure 2. Suppose the angle between the highway bend and the steel tower at the oilfield wellhead is 15°. Draw a line from the highway bend toward the oilfield wellhead steel tower that is perpendicular to the 64° bearing line; measurement on the map shows this distance to be 16 meters (1 mile). Therefore, along the 64° bearing line, your position is:

Protractor

Structure

The dial is supported by jewel bearings, and all its moving parts are immersed in a damping fluid. This damping fluid ensures that the dial returns to its zero position quickly, allowing the dial face to rotate smoothly and without vibration.

How to use

People generally prefer to read with their right eye, though some find it easier to use the left eye due to visual differences. It’s best to use both eyes simultaneously and make sure your hand doesn’t block your line of sight.

Hold the instrument in front of your eyes with your hand, orienting the circular window to the left. Adjust the instrument’s elevation to bring the target into sight until the horizontal scale line is aligned with the object being measured, then read the scale through the eyepiece. Due to an optical illusion, the horizontal scale line appears to extend continuously outward toward the object, making it easy to verify that the scale line is properly aligned with the target and enabling quick, accurate readings, as shown in Figure 3.

The left-hand scale displays the slope angle in degrees, measured from the eye level; the right-hand scale shows the height difference from the same eye level to the point being measured, expressed as a percentage of the horizontal distance. An example is provided below to illustrate the calculation process.

To measure the height of the pole at a horizontal distance of 25 m, refer to Figure 4. Tilt the instrument until the horizontal bubble level is aligned with the top of the pole, and record the reading as 48%. Since the horizontal distance is 25 m, the height of the pole is calculated as follows: 48% × 25 = 12 m. To this result, add the height of the observer’s eye above the ground—for example, 1.6 m—yielding a final total of 12 + 1.6 = 13.6 m. This is the height of the pole.

For precise measurements, especially when measuring from a slope, two readings are required: one from the eyepiece to the top of the pole and another from the eyepiece to the base of the pole. If the base of the pole lies below eye level, the percentage value obtained must be added to the reading. For example,

Figure 5: If the top reading is 41% and the bottom reading is 13%, then the height of the pole at a horizontal distance of 25 m is: (41% + 13%) × 25 m = 54% × 25 m = 13.5 m. Conversely, if the base of the pole is above the eye level, the top reading should be reduced by the bottom reading. For example, in Figure 6, if the top reading is 64% and the bottom reading is 14%, then the height of the pole is:

(64-14)%×25m=50%×25m=12.5m

If you want to estimate height by mental calculation, we recommend choosing a horizontal distance of 50, 100, or 200 meters, as this makes the calculation simpler. All percentage readings are based on horizontal distance; therefore, if you are measuring along a slope, an error will be introduced. To obtain accurate results, a correction must be applied (though this correction can be neglected for very gentle slopes).

The trigonometric relationships are:

H = h × cos a

Where: H = the true or correct height

h - observed height

a-Ground slope angle

The correct horizontal distance can also be obtained from the above equation.

Where: h – the distance measured along the ground

H-Correct horizontal distance

When calculating horizontal distance from ground-measured distances and slope angles, if the slope angle is measured from eye level to the base of the pole, an error will be introduced (because there is a certain vertical distance between the eyes and the ground). However, measuring the slope angle directly along the ground is cumbersome and inconvenient. To avoid introducing such errors when measuring the slope angle, a visible marker can be set up at eye level at the foot of the slope (or a pole can be placed to indicate the eye-level position), thereby making the two measurement lines parallel. By aligning the eyepiece with this point during measurement, the correct slope angle of 9° can be obtained, as shown in Figure 7. Figure 7 illustrates the two calculation methods.

Method 1: The horizontal distance measured along the ground is 25 m, the slope angle is 9°, and the percentage readings at the top and bottom of the pole are 29% and 23%, respectively.

Calculate 29% + 23% = 52%.

25m × 52% = 13m

13 m × cos 9° = 12.8 m

Method 2: Multiply cosa (where a is the slope angle) by the ground-measured distance of 25 m.

cos 9° × 25 m = 24.7 m

24.7 m × (23 + 29)% = 12.8 m

This example demonstrates that when the slope angle is 9°, the height error is only 2.3%, whereas at a slope angle of 35°, the error rises to 18%.

Harbin Optical Instruments Factory Co., Ltd.

HARBIN OPTICAL INSTRUMENT FACTORY LTD.

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