use of dogs 4. Secure handwheel 14 of the stopper of the limb of the traversing angles. Release
handwheel 11 of the device brake.
6.3 Operation with Device
The device is employed in the working position by two persons; an observer and a reader. When the
object is detected with an unaided eye, the observer aims the device at the object by using an
approximate sight and then observing through the binocular telescope brings the cross-hairs centre and
the object image in coincidence and keeps the object image at the cross-hairs centre by rotation of the
device using the handles. At the same time the reader takes readings of the values of the traversing
angles and angles of elevation from the scales. Viewing through the tell-tale pipe the reader also sees to
it whether the device is aimed at the object correctly if necessary.
Take readings of the scale of the horizontal limb by the scale of the limb and nonius (Figure 7).
If the zero line of the nonius is precisely aligned with any line of the limb scale one takes reading using
only the zero line of the nonius and limb scale, because one knows a division value of the small division
of the limb scale equal to ten divisions of the deflection as well as a division value of the large division
equal to one hundred divisions of the deflection. One takes reading of hundreds of divisions of the
deflection by the nearest figure of the limb scale positioned on the left side of the zero line of the nonius.
Then one takes reading of the small divisions of the limb scale positioned between the line designated
with this figure and the line coincident with the zero line of the nonius, thus determining the tens of
divisions. After doing so the results are to be added. To facilitate taking reading every fifth line of the limb
scale is elongated.
Example.
The line of the scale limb positioned closely to the left side of the zero line of the nonius is
designated with 59. The nineth line of the limb scale is aligned with the zero line of the nonius (if counting
from the line designated with 59).
After addition of readings (59-00 + 0-90) one obtains 59-90 (Figure 8).
If the zero line of the nonius is not aligned with any limb line one takes reading to the nearest line of
the limb scale on the left of the zero line of the nonius in the way mentioned above and determines the
units of the deflection divisions by the nonius (with accuracy of the nearest even figure). To perform this
one takes reading of the divisions from the zero line of the nonius to the nonius line which is aligned with
any line of the limb scale and multiplies the read number of the divisions by two, as the division value of
the nonius scale is equal to two divisions of the deflection (0-02). The obtained value is the value of
correction in divisions of the deflection which is added to the result obtained before.
Example.
It is required to take readings from the scale of the horizontal limb in compliance with figure
9. In the given case the large line of the limb scale nearest to the left of the zero line of the nonius is
designated with 39. Prom this line one reads small divisions (seven) of the scale up to the zero line of the
nonius. Add readings (39-00 + 0-70), obtain as a result 39-70. Then read the divisions from the zero line
of the nonius to the nonius line coincident with the line of the limb scale (the third line). Multiply the result
by 2, obtain 0-06. Add this result to readings (39-70 +0-06) obtained before and obtain the value of
reading of the horizontal limb scale equal to 39-76 read with accuracy up to two deflection divisions.
The readings of the vertical limb scale (Figure 10) are taken from the scale and by the nonius like the
readings of the horizontal limb and with the like accuracy. The positive angles are read by the scale lines
and nonius painted white and the negative ones are read by the lines painted red. Besides, when taking
readings of the positive angles one takes reading up to the line of the limb scale nearest to the right of
the zero line of the nonius, and when taking readings of the negative angles one takes readings up to the
limb scale line nearest to the left of the zero line of the nonius.
Example.
It is required to determine the scale reading of the vertical limb in compliance with figure 11.
As the lines of the positive angles are positioned against the nonius the reading is taken up to the line
of the limb scale nearest to the right of the zero line of the nonius. In the given case such line is the line of
the limb scale designated with figure 2.
There are-no small divisions between the line designated with figure 2 and the zero line of the nonius,
therefore the reading is +2-00. Take reading of the number of divisions from the zero line of the nonius up
to the line of the positive nonius (painted white) coincident with any line of the limb scale. In the given
case this in the first line, i.e. 0-02. Add the readings (2-00+0-02) and obtain the reading value of the
vertical limb equal to 2-02 read with accuracy up to two divisions of the deflection.
The angles in the horizontal and vertical planes are measured by the subsequent aiming of the device
at two points, the angular distance between them is determined by two readings of the aimed device.
When measuring angles of elevation one should take into consideration that in obtaining two readings
of the similar signs the true value of the angle to be measured is equal to the difference in the largest and
smallest readings, and when obtaining the readings of different signs the angle value is equal to the sum
of their absolute values.
Determination of the range to the object by its angular value should be carried out in the following way:
