1000 aiming circle c2

8/8/2019 1000 Aiming Circle C2

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INFANTRY SCHOOL

HANDOUT #1000

OPI: MOR AIMING CIRCLE C-2 REVISED: SEPT 00

GENERAL

1. Introduction. The Aiming Circle C-2 is a precision instrument for measuring horizontal and verticalangles. It is used as an aid to survey and is called a "director" by the artillery. To avoid damage to gears andthreads, it must be carried or transported in the case and held in an upright position to prevent damage to thecompass or the levelling screws.

RADIATION WARNING

1. The C-2 Aiming Circle uses Tritium as a light source to illuminate the scales, levels, compass and reticle.

The Tritium is in a gaseous state, sealed in zinc coated glass containers. There is no hazard to the user unless the sealed containers are broken, then there are two hazards:

a. The hazard from the released gas is negligible unless it is inhaled. The gas disperses quickly however,should a container break in a confined space such as a vehicle, should be immediately evacuated by

personnel and aired.

b. The glass splinters pose a hazard and the following action should be taken when disposing of it:

(1) Gloves should be worn to prevent toxic chemicals from entering into the blood system;

(2) The contaminated area should be wiped off with a damp cloth;

(3) The fragments and cloth should be placed in a suitable container like a plastic bag, empty metalcan or heavy waxed paper and disposed of as normal waste;

(4) Hands should be thoroughly washed with soap and water; and

(5) Any cuts or abrasions caused by the breakage, or received during the cleaning up must be dealtwith as follows:

(a) the injured area shall be exposed and washed with soap under running water to washout any foreign matter, and

(b) the casualty must be sent as quickly as possible to the nearest medical officer, even if the injuries would normally be regarded as trivial.

DESCRIPTION

2. Main Components

a. Levelling Base. The levelling base consists of the following parts:

(1) Base. The Aiming Circle is permanently attached to the base by means of three adjustablescrews which are secured by a spring locking plate. The base, which also acts as thecontainer base, is circular in shape and has a rubber gasket. Together with the instrumentcover, it makes the instrument water and dust proof. On the bottom, a spring-loaded dust

cover protects the threaded boring which is used when fixing the Aiming Circle to theinstrument stand C2. On top of the base, receptables are provided for a light-colouredfilter, a dark filter and a parallax shield. Three wells are provided for the bottom ends of the levelling screws.

(2) Locking Plate. The locking plate is secured to the base by means of the three adjustablescrews. This in turn secures the bottom of the levelling screws and thus the director to the

base.

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(3) Supporting Base. The supporting base is located between the locking plate and thehorizontal scale. It supports the horizontal scale and the body of the director. The ends of the arms are bored and threaded to accommodate the tops of the levelling screws. Capstanscrews are provided for each levelling screw so that tension may be adjusted. A circular spirit level is attached to the side of one of the legs and is used when levelling the director

for normal use. A lower gear is fitted on the opposite side of the supporting base. Alocking cover is provided to prevent accidental use of the lower gear.

b. Lower Gear. This consists of a worm and spindle with a fluted knob and a quick-release lever atone end. The worm engages the lower worm gear of the horizontal scale and is disengaged whenthe quick-release lever is raised.

c. Horizontal Scale. This consists of a horizontal scale with an upper and lower worm gear. The scaleis graduated every 100 mils and labelled every 200 mils. It is pivoted on the base and is rotated(traversed) by means of the lower gear, or it can be swung freely when the quick-release lever os thelower gear is raised. When the horizontal scale is rotated, the body and telescope also rotate withoutchanging the reading of the scale.

d. Body. The body is pivoted on the horizontal scale and is rotated (traversed) upon it by means of theupper gear mounted on the side, or it can be swung freely when the quick-release lever of the upper gear is raised. A black arrow is marked on the body under the eyepiece of the telescope and a redarrow under the object glass; both are used to read the horizontal scale. On the side of the body is atubular spirit level for accurate levelling. The compass needle release is also located on the body.

e. Upper Gear. This consists of a worm and spindle with a knurled knob on one end, a micrometer scale on the other end, and a quick release lever. The worm engages the upper worm gear of thehorizontal scale and is disengaged when the quick-release lever is raised. One turn of the knobrotates the body and scale through 100 mils. The scale is graduated every mil, accentuated every 5mils, and labelled every 10 mils. The micrometer scale is read against an arrow fitted to the spindlecase and is used in conjunction with the horizontal scale.

f. Quick and Slow Gears

(1) The quick motions of the upper and lower gears should be employed freely, and should beused for all movements exceeding 200 mils.

(2) To avoid disturbing the aiming circle, the operator should avoid walking around it. Heshould place himself at the position from which he is going to observe, depress theappropriate quick release lever, and bring the eyepiece into line.

(3) Correct use of the quick and slow gears will largely eliminate backlash, a certain amount of which is present in any combination of gears.

(4) When the director is swung right, the last motion must be traverse left. When it is swungleft, the last motion must be traverse right. The telescope is swung at least 100 mils past

the object to be laid upon, then traverse back to it.

(5) For simplicity, swing right-traverse left (SRTL), should be used for all operations exceptwhen centering the compass needle. In this case, traverse left and traverse right are used.

(6) When SRTL is detailed, it is understood that traverse left (TL) may be employed withoutthe initial swing right (SR) only if a small movement to the left is required. Moreover, if alarge movement to the left is required when SRTL is detailed, it is permissible to carry outthe movement by using swing left (SL) followed by SRTL.

g. Elevation Drum. The elevation gear and telescope are fitted to the elevation drum. The drum issupported by two supports. The manufacturer's name, the model number and serial number arelocated on one of the supports. A bracket is also provided for retaining the brass screwdriver:

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(1) Telescope. The eyepiece is provided with a bakelite eyeguard. The object glass oppositethe eyepiece is protected by a rain shade. The telescope has a view of approximately 160mils with a magnification of 5 power. The reticle pattern (Fig 3) can be focussed byrotating the eyepiece (+6 to -6 diopters). A glass diaphragm is fitted inside the telescope; itis engraved with horizontal and vertical lines with graduations every 5 mils, accentuated

every 10 mils, and labelled every 20 mils. A standard 1/100 verticle stadia intercept isengraved on the diaphragm. The stadia intercept consists of three horizontal graduationswhich provide means of measuring distance.

(2) Elevation Gear. This is mounted on the drum to the right of the telescope. It consists of aworm and spindle with a micrometer on one end, and quick-release and knurled knob onthe other. The worm engages the vertical worm gear, which is fixed to the right support,and is disengaged when the quick-release lever is raised. One turn of the knob rotates thedrum and scale 100 mils about the vertical gear. The elevating scale is scribed every 100mils from -650 to +1600 mils.

h. Record Plate. The record plate is fitted to the side of the instrument cover and is used for recordingthe difference between magnetic and grid bearings, bubble correction, compass error and the dateand place at which these corrections were determined.

i. Vernier and Magnetic Variation Scales

(1) The sealed compass is located on top of the body.

(2) The compass needle is kept clear of its pivot and clamped by a compass needle releasespring. Two metal weights are fitted to the compass needle to adjust for dip. When thecompass is to be used, the compass needle release, under the object glass, is raised; thislowers the compass needle to its pivot and allows it to swing free. The needle is painted

black with the north tip painted red. The needle is marked "N" for north. The needle isviewed correctly when the black tip shows above the red tip.

(3) The vernier and magnetic scale (Fig 1) is located under the object glass. The vernier isadjusted with a small brass screwdriver and an adjusting screw located directly under thevariation scale.

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Figure 1 Vernier and Magnetic scale

j. Case. The padded case is made of a heavy plastic fitted with moulded high-density foam. There aretwo slots cut into the mould for the carrying straps of the instrument cover. There is a radiationwarning decal on the outside of the case.

k. Tripod Instrument, C2. The platform is supported by three telescopic legs which are secured byclamping screws. The legs are attached to the platform with three tension clamps. A securing strapis fixed to one leg and is used for holding the legs together for carrying. An adjustable shoulder strap is fixed to another leg. A tool case with a 6mm hexagonal wrench and plumb-bob assembly issecured to the inner side of one of the legs. The platform has a large central opening. inside thisopening is the securing screw to hold the director to the tripod. The securing screw moves in aslotted hinged arm so that the instrument can be moved on the platform to centre over a survey

point. A plastic cover is fitted to the platform when the director is not in use.

l. Lighting System. The director is fitted with a nuclear lighting system, which illuminates all thescales, spirit bubbles, compass and the reticle pattern of the telescope. When the telescope is

elevated to 1600 mils, the light on the elevation cylinder opposite the telescope provides a laying point for night use.

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SET UP

3. Instrument Tripod, C2

a. Loosen the clamping screw and extend each leg in turn, leaving at least six inches of the lower portion engaged with the upper portion, and tighten the clamping screw. The top of the stand must

not rest on the ground during this operation. b. Release the strap, open the legs and set the stand on the ground.

c. Press each leg firmly into the ground, supporting the inside of the leg with the knee.

d. Roughly level the head of the stand by lengthening or shortening the legs as necessary.

4. Placing Aiming Circle on Stand

a. Remove the protective cover from the head of the stand and fix it to the bracket of the leg.

b. Fit the Aiming Circle to the stand ensuring that the securing screw is central in the opening; this isnecessary when setting up over a survey point.

c. Tighten the securing screw.

d. Remove the protective cover from the aiming circle.

5. To Level the Aiming Circle

a. The circular level is used to level the aiming circle for normal use. The tubular level is used as acheck if needed.

b. The following drill is used for levelling the aiming circle for normal use:

(1) the stand is roughly levelled by adjusting the legs,

(2) turning levelling screws A and B opposite to one another, bring the circular level bubble tothe centre of its run. The bubble will follow the direction of the left thumb,

(3) turning levelling screw C, bring the bubble to the centre of the scribe circle,

(4) further adjustments, if required, are made by following steps in sub-paras 2 and 3 until the bubble is in the centre of the scribed circle. The aiming circle is now ready for normal use.

PACK UP

6. Although speed will be important care must be taken to prevent damage to the screws and gears.

a. Roughly centre all levelling screws and set all scales, except the magnetic variation scale, to zero.Ensure the bearing "0" is below the black marker.

b. Replace the metal cover and engage the clamps.

c. Unscrew the securing screw, at the same time placing the other hand on top of the metal cover.

d. Set the aiming circle into the container and close the lock.

e. Replace the protective cover on the tripod platform.

f. Lift up the tripod and close the legs.

g. Close the legs, tighten the clamping screws on each leg and strap the legs together.

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MAINTENANCE

7. The Aiming Circle C-2 is an instrument and it should be handled accordingly. When not in use, itmust be placed in its case to prevent accidental damage. The following points must be strictly followed:

a. DO NOT turn the scales by the micrometer. The knob in front is to be used to prevent unnecessary

wear of the scales. b. Normal maintenance is keeping the aiming circle clean and dry. The telescope lenses are cleaned in

the same manner as binoculars.

c. DO NOT cover the aiming circle with oil or other substances.

d. If the eyepiece or adjusting screws bind or have seized, the aiming circle must be turned in for repair.

e. The tripod requires the same maintenance as the aiming circle. Ensure that the accessories arecomplete and in good repair. It is important that the tripod remain clean.

TECHNICAL SPECIFICATIONS

8. Physical Data:

a. Manufacturer Wild Heerbrugg Ltd.Model G10 Goniometer.

b. Main Equipment Operating Configuration:

Length 14.0 cmWidth 14.0 cmHeight 22.9 cmWeight 3.4 Kg

c. Main Equipment Cased Configuration:


d. Main Equipment Stowed for Shipping:


e. Shipping Case:


f. Tripod:

Length 110.5 cm (closed)Width 19.1 cmWeight 6.4 Kg

9. Optical Data:

a. Telescope:

Magnification 5xField View 160 milsEyepiece Adjustable +6 to -6

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b. Reticle:

Type EtchedAlignment Reference Cross-line patternGraduation Range Cross-line centre dot 50 mils vertical and horizontal all directions from

centre doton cross lines.

Graduation Interval 5 mils Numbering Interval 20 mils.

10. Mechanical Data:

a. Elevation Scale:

(1) Coarse Reader

- Range -650 mils depression to 1600 milselevation

- Graduation Interval 100 mils- Numbering Interval 200 mils

(2) Fine Reader

- Range 0 to 100 mils- Graduation Interval 1 mil- Numbering Interval 10 mils in bothelevation anddepression.

b. Upper Azimuth Scale:

(1) Coarse Reader

- Range 6400 mils- Graduation Interval 100 mils- Numbering Interval 200 mils

(2) Fine Reader

- Range 0 to 100 mils- Graduation Interval 1 mil- Numbering Interval 10 mils increasingazimuth

c. Lower Azimuth Gear Mechanism: No scales, worm gear mechanism range 6400 mils for orientation.

d. Compass Declination Scale:

(1) Main Scale

- Range 0 to 600 mils East and West- Graduation Interval 50 mils- Numbering Interval 200 and 400 mils East and West

(2) Vernier Scale

- Range 0 to 10 mils East and West- Graduation Interval 1 mil- Number Interval Nil

11. Illumination

Type Tritium Light Sources

12. Working Accuracy

The working accuracy is as follows:

Elevation Measurements 1 milAzimuth Measurements 1 milAzimuth Error using Compass 5 milsAngle Measurements using Reticle 2 mils

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READING SCALES

13. Elevation Scale. The elevation scale is read against a black arrow on the right support. Themicrometer scale is graduated every mil, accentuated every 5 mils, and labelled every 10 mils. Angles of depression are read using the red-coloured figures. The micrometer scale is read against an arrow fitted to thespindle case and is used in conjunction with the elevation scales.

14. Horizontal (Bearing) Scale

a. Use the pointer under the telescope eyepiece (black) unless instructed to use the object glass pointer (red).

b. Note the values of the 100-mil graduations on each side of the pointer, then read the 100-mil mark on the right.

c. Read the micrometer scale. Note the value of the 10-mil graduation on each side of the pointer.Read this pointer to the nearest mil.

15. Vernier and Magnetic Variation Scale. The vernier has ten graduations east and west of centre.Each graduation is 5 mils. The variation scale is graduated every 50 mils and labelled every 200 mils from 0 to 600mils east and west.

CALIBRATION

16. Definitions

a. Swing. To "swing" the aiming circle, the telescope is rotated with one of the quick-release leversraised. An aiming circle is said to "swing right" when rotating clockwise and "swing left" whenrotating counterclockwise.

b. Traverse. To "traverse" the aiming circle, the telescope is rotated by one of the slow motionspindles. An aiming circle is said to "traverse right" when rotating clockwise and "traverse left"when rotating counterclockwise.

c. Closing. At the completion of every operation, the aiming circle should be relaid on the point firstobserved, and the reading noted and compared with the original reading. This check known asclosing ensures that an unintended movement of the aiming circle is detected. The second readingshould agree with the first reading within one mil.

d. Reference Object (RO) - It may be:

(1) a point to which a bearing is determined,

(2) a selected point to measure angles to other points in a round of angles, and

(3) a point to which the bearing is known. A Regimental Survey Control Point (RSCP) may

show as many as five such points.

17. Magnetic Variation Scale. The aiming circle compass is susceptible to local magnetic fields.Compass error can be minimized by observing the suggestions in Chapter 5, Sect 5, para 60 of the CFPB-GL-306-008/FP-001:

a. The magnetic variation scale permits direct reading of grid bearings.

b. Once the magnetic variation scale is set, the line of sight through the director telescope is in thedirection of grid north when the compass needle is on its laying mark.

c. Determine the magnetic variation and check the record plate on the cover for the compass error, if recorded. Combine this as described in Chapter 5, Section 5 of the CFP B-GL-306-008/FP-001,

d. Before beginning any observations which involve the use of the director compass, the observer reads the magnetic variation scale. If the scale is not set at the recorded variation, carry out thefollowing drill:

(1) insert the small screwdriver into the adjusting screw-head,

(2) turn the screw until the centre line of the vernier is set against the nearest 50-mil graduation below the variation required, using east or west readings as applicable,

(3) continue to turn the screw slowly in the direction of increasing variation until the required5-mil graduation of the vernier comes into coincidence with a 50-mil graduation of thevariation scale (eg, if the magnetic variation is west, count the 5-mil graduations startingfrom the left end of the vernier, and vice versa if the magnetic variation is east),

(4) check against gross error by reading the variation scale at the position of the centre line of the vernier,

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(5) remove the screwdriver from the adjusting screw and replace it in the socket provided. TheC2 aiming circle can only be set to the nearest 5 mils,

(6) again check the reading of the magnetic variation scale,

(7) figure 2 illustrates the magnetic variation scale set at 285 mils west. The drill would have been carried out as follows:

(a) the magnetic variation is rounded off to the nearest 5 mils (ie, 283 rounded tonearest 5 mils = 285 mils),

(b) the first setting is made by setting the centre line of the vernier at 250 mils west,

(c) the seventh graduation from the left end of the vernier is brought into coincidencewith the next 50-mil graduation of the variation scale. Seven graduations of thevernier is equal to 35 mils; total variation set equals 285 mils.

NOTEA second method, which requires a survey point and known grid bearings to RO's,is quicker and just as accurate. It also can be used to determine the compass error of an aiming circle.

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Figure 2Magnetic variation at 285 mils W

18. Calibration

a. Set up aiming circle over the survey point:

(1) set up the instrument stand ensuring that the head of the stand is directly over the survey point,

(2) fit the aiming circle to the tripod,

(3) fit the plumb-bob assembly to the aiming circle securing screw by forcing the tube adapter into the bottom of the securing screw,

(4) loosen the securing screw slightly and move the aiming circle about the tripod head untilthe plumb-bob is accurately centred over the survey point,

(5) tighten the securing screw,

(6) replace the plumb-bob assembly in its case on the leg of the director stand.

b. Level the aiming circle and set the bearing of the RO on the bearing scales.

c. Lay on the RO using the lower bearing gear quick release so the pre-set bearing is not disturbed andclose the hinged cover over the lower gear using the upper gear. Set 0 on the horizontal scale.

d. Insert the tip of the attached screwdriver into the adjusting screw for the magnetic variation scaleand lift the compass release.

e. Look into the compass viewing magnetics by turning the screw driver, align the two tips of thecompass needle. Ensure that the red tip appears at the bottom then lock the compass needle.

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f. Record the vernier scale setting.

g. Calculate the difference between the vernier scale reading and the local map variation. Thisdifference is the compass variation for that aiming circle. Knowing this built-in error, you can nowapply it to a map variation when a survey point is not available to calibrate your aiming circle.

h. Mark this on the record plate on the cover including date and place.19. Test. To carry out this test, the grid bearings to a reference object must be known.

a. Using the upper bearing gear, set the scale to 0;

b. Using the lower gear, and with the compass needle released, bring the tips of the compass needleinto alignment, ensure that the red tip of the needle appears at the bottom;

c. swing right, traverse left using the upper gear, lay on the reference object. Reading to the referenceobject must agree with the known bearing to within 5 mils. If it differs by more than 5 mils, thevariation must be set again.

ORIENT TO GRID NORTH

20. Orient to Grid North is as follows:

a. Set up and level the aiming circle.

b. Set the horizontal scale and micrometer to zero (black on red).

c. Using the lower gear quick release swing the instrument to approximately north.

d. Lift the compass release, look into the magnifier and turning the lower gear align the two tips of thecompass needle. Ensure that the red tip is at the bottom.

e. Lock the compass and close the hinged cover over the lower gear.

f. Turn the upper gear at least 50 mils away from zero.

g. Lift the compass release again, look into the magnifier and by turning the upper gear align the twotips of the compass needle again. Ensuring that the red tip of needle appears at the bottom.

h. As soon as alignment is complete, remove both hands from the instrument.

i. Check the horizontal scale micrometer, it should be within 5 mils either side of zero. If so, theaiming circle is now oriented on grid North to an accuracy of +5 mils.

j. If the reading on the horizontal scale micrometer is greater than 5 mils left or right of zero, repeatsteps b to i.

k. All horizontal readings taken with the aiming circle after completion of the drill are grid bearings.

l. Choose an RO and record the reading to it.

m. Quick Check with Prismatic Compass:

(1) From a point at least 50 meters from the director, and in line with the aiming circle and thereference object, determine the grid bearing to the reference object using the prismaticcompass;

(2) If the grid bearing agrees to within 20 mils of the bearing obtained with the aiming circlethen the aiming circle is accepted as correct;

(3) If the grid bearing does not agree to within 20 mils, it must be assumed that local magneticattraction is present and a new site must be chosen for the aiming circle.

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MEASURE BEARINGS

21. The Procedure to Measure Bearings is as follows:

a. Set up and level the aiming circle. Confirm the magnetic variation, orient it to grid North and selecta RO. Lay the vertical line of the reticle is laid on the object and focused. To counteract any effect

of the reticle not being truly vertical, the object should be brought into the centre of the telescopefield with the elevating gear.

Note the bearing for later reference.

b. Check for Location Magnetic Attraction. A check for local magnetic attraction is conductedwhenever time permits. A quick check, described at Sect 5, para 70, Chap 5 of B-GL-306-008/FP-001, may be conducted with a prismatic compass when time is very limited:

(1) Set up the director afresh, in a position at least 50 metres away from and in line with itsoriginal position and the reference object;

(2) Determine the grid bearing to the reference object using the aiming circle compass:

(a) if the new bearing does not differ from the old by more than 10 mils, the mean isaccepted,

(b) if the new bearing does differ from the old by more than 10 mils, the procedure isrepeated from a third position in the same line and at least 50 metres from either of the other two positions;

(3) After having determined three bearings to the same reference object, the following procedure is adopted:

(a) if the third bearing does not differ from either of the previous bearings by morethan 10 mils, the mean of the three bearings is accepted,

(b) if any two of the three bearings agree to within 10 mils, while the third differs bymore than 10 mils from either, the mean of the two is accepted,

(c) if no two bearings agree to within 10 mils, it is assumed that local magneticattraction is affecting the compass and a new site is chosen for the aiming circle.

c. Measure the bearings for the task. The black indicator will give a bearing while the red indicator infront will give a back bearing. After noting the bearings lay back on the RO and check the bearing.If it is greater than + 5 mils, all work must be done again.

22. MEASURE DISTANCES AND ANGLES

a. Description. The stadia rod is a rigid pole which can be fixed in the vertical position. It is clearly

marked with divisions of different colour, in 10 cm lengths (21 divisions) and two end divisions of 22cm which also serve as spikes for implantation into the ground. Some versions may have theupper section (1 meter) as a solid colour and the lower section marked in 5 divisions (20 cm).

(1) this method utilizes the Mil Formula. The stadia intercept of the reticle pattern (Fig 3) isused to measure the vertical angle. It is considered accurate to 400 metres only. This is

because the standard stadia rods are 2 meters long. if it is longer, the distance can be proportionally greater.

(2) corrections for differences in altitude are not necessary unless it is greater than 5 meters andthe angle of sight is 150 mils or more (as indicated on the elevation gear).

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.

20

40

40

20

20 2040 40

Stadia intercept

}

Figure 3 Stadia intercept

b. The procedure to measure distances is as follows:

(1) Set up and level the aiming circle.

(2) Look through telescope and lay top stadia intercept mark on the top of the upper division(Fig 4).

If the distance is too great and half vertical intercept must be used, the center graduation is placed on the top of the upper division (Fig 5).

(3) Count the number of divisions from the top of the rod to where the lower graduation cutsacross division:

(a) with full vertical intercept, the count is expressed as a decimal then multiplied by10 ( fig 4). The stadia rod shown in has small divisions on the lower half. Theupper half is counted as 100 meters and the lower divisions counted as 20 meterseach, subdivided by estimation,

140 Meters

10 cm20 cm

160 Meters

100 cm

120 Meters

20 cm

Figure 4 Full Vertical Intercept on Stadia Rod

(b) if half vertical intercept is used, the division count is doubled then applied as for full vertical intercept (Fig 5).

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220 Meters

10 cm

240 Meters

20 cm

100 cm

260 Meters

20 cm

Figure 5 - Half Vertical Intercept on Stadia Rod

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1000 aiming circle c2

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