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TABLE OF CONTENTS PM-5/1520 ................................................................................................................ 4 OPTICAL HEIGHT METER ................................................................................ 4 INSTRUCTIONS FOR USE ............................................................................... 4 MEASUREMENT OF HEIGHT ........................................................................... 5 INSTRUCTIONS FOR USE OF NOMOGRAM .............................
PM-5/1520 OPTICAL HEIGHT METER Suunto Height Meter PM-5/1520 is an instrument for measuring heights, especially heights of trees, with great accuracy and speed. The body of the instrument is corrosion-resistant anodized aluminium-alloy. The scale card runs on a special bearing in a hermetically sealed plastic container filled with a liquid which guarantees that it runs freely and stops quickly.
MEASUREMENT OF HEIGHT The actual measurement of the height of the tree should be done from the distance measured in the following way: the observer sights the top of the tree with both eyes open. The object sighted, the hair line and the scale will all be simultaneously visible in the instrument`s field of vision. As soon as the hairline coincides with the top of the tree, the tree height can be read off (in this example, from the 20 m scale on the left of the instrument).
exactly correct result you have to proceed as stated below. On level ground, the tree top readings is usually sufficient: one only has to add the height of the observer`s eye level (1,60 m in this case), which is already known.
INSTRUCTIONS FOR USE OF NOMOGRAM If the distance, because of very uneven ground, cannot de determined horizontally as stated above, the nomogram supplied with the instrument should be used. ESTABLISHING THE BASIC DISTANCE Because this instrument does not incorporate a prism, the basic distance e.g. 15 m has to be determined using a tape measure along the ground. Take the top and base readings and add or subtract them to get the apparent height.
L-20 2 4 5 6 m m 20 20 19 18 19 3 17 18 4 16 m 0 1 2 Downhill Fallendes Gelände Terrain déclinant Medlut Maasto laskee 7 8 5 9 10 11 12 13 17 15 14 6 7 8 16 13 15 Uphill Ansteigendes Gelände Terrain mountant Motlut Maasto nousee 12 14 11 10 13 9 12 9 14 11 16 18 12 13 Corrected height Wahre Höhe 17 19 14 20 15 21 16 8 Base reading Ablesung beim Anvisieren d.
PM-5 OPTICAL READING CLINOMETER The sturdy pocket-size construction renders the SUUNTO CLINOMETER most suitable for every type of work. Easy for rapid reading through a parallax-free lens is incorporated into the design. Sighting and scale reading are done simultaneously. There are no screws to turn, no bubbles to center, and nothing to adjust.
10 + and – ft.
Specifications Weight: 120g/4,2 oz. Dimensions: 74 x 52 x 15 mm / 2 3/4" x 2" x 5/8". The optical scales are graduated in degrees from 0° to +/-90°, and 0% to +/-150 %. A table of cosines is imprinted on the back of the instrument. Accuracy Can be read directly to one degree or one per cent. Can be estimated to 10 minutes or 1/5 of 1 per cent, the latter naturally applying to readings around the zero level.
INSTRUCTIONS FOR USE Readings are usually taken with the right eye as shown on the title page. Owing to differences in the keenness of the sight of the eyes and because of personal preferences the use of the left eye is sometimes easier. It is of prime importance that both eyes are kept open. The supporting hand must not obstruct the vision of the other eye. The instrument is held before the reading eye so that the scale can be read through the optics, and the round side-window faces to the left.
The task is to measure the height of a tree at a distance of 25 m/82 ft. on level ground. The instrument is tilted so that 12 m / 32 ft. the hair line is seen against the tree-top (apex). The reading 48 % obtained will be 48 per cent (ca 25,5° 25 1/2°). As the distance is 1,6 m / 5.5 ft 25 m/82 ft. the height of the tree is 48/100 x 25 m = ca. 25 m / 66 ft. 12 m or equally 48/100 x 82 ft. = ca. 39 ft. To this must be added the eye’s height from the 10,25 m 27 ft. ground, e.g. 1,6 m or 5 1/2 ft.
When the trunk base is above eye level, the base reading is subtracted from the apex reading, and the total height is the difference percentage of the horizontal distance. For example, if the apex reading is 65 % and the base reading 14 %, the total height is (64-14)/100 x 25 m = 50/100 x 25 m = 12,5 m or equally in feet (64-14)/100 x 82 ft = 50/100 x 82 ft = 41 ft. When calculations are made mentally it is advisable to use measuring distance of 50, 100 or 200 m/ft. for the sake of simplicity.
The trigonometrical correlation is H = h x cos α Where H is the true or corrected height, h is the observed height and α (alpha) is the ground slope angle. With the aid of the above equation the correction can also be made in the distance. In this case h means the distance measured along the ground and H is the horizontal distance sought. If the corrected distance is used no correction in the height observed is needed.
Calculate: 29- 52 23- + --------------= --------100 100 100 Take 52 per cent of 25 m/82 ft. This is 13 m/42,6 ft. Multiply this by the cosine of 9 degrees. 0,987 x 13 m = 12,8 m or equally in feet 0,987 x 42,6 ft. = 42 ft. Method 2. Multiply the ground distance by the slope angle cosine. 0,987 x 25 m = 24,6 m or equally in feet 0,987 x 82 ft. = 80,9 ft. Add percentage readings as above and take the sum percentage of the corrected distance.
NOMOGRAPHIC HEIGHT CORRECTION When the accompanying nomograph is used, all correction calculation becomes unnecessary. Only a ruler or some other convenient object with a straight edge is needed to obtain the nomographical solution. The nomograph is used by placing the ruler so that its edge intersects the angle scale on the left at the slope angle point and the observed height scale (on the right) at the pertinent point.
