(a) For example, in cross-sectional work, terrain irregularities may cause elevations to go
beyond the automatic level's range from a setup. A hand level is useful for extending approximate
elevations off the control-survey line beyond the limits of the automatic level. For greater stability, the
hand level may be rested against a tree, a Philadelphia rod, or a range pole.
(b) On a hand level, a level vial is mounted atop a slot in the sight tube in which a
reflector is set on a 45€ mirror. This allows the observer, while sighting through the tube, to see the
landscape or object, the position of the bubble in the vial, and the index line at the same time. The hand
level has no magnification capabilities, therefore, the distances sighted are relatively short.
(c) In Figure 5-5, view A shows a Locke hand level that is very simplistic in design and
view B shows an Abney hand level (or clinometer) which has a reversible, graduated arc assembly
mounted on one side and may be used for measuring vertical angles and percent of slope. The lower
side of the arc is graduated in degrees, and the upper side is graduated in percent of slope. The level vial
of the Abney hand level is attached at the axis of rotation of the index arm. When the index arm is set to
zero, the instrument is used like a Locke hand level. When it is used as a clinometer, the object is
sighted and the level tube is rotated about the axis of rotation until the bubble is centered. The
difference between the line of sight and the level-bubble axis can be read in degrees or percent of slope
from the position of the index arm.
Figure 5-5. Hand levels
PART B - FIELD EQUIPMENT
5-2. Hand Tools. The term field equipment, as used in this lesson, includes all devices, tools, and
instrument accessories used in connection with field measurements.
a. When conducting a survey across rough terrain, various types of tools will be needed to clear
the line, that is, cut down brush and other natural growth as needed (see Figure 5-6). Surveying
procedures usually permit the bypassing of large trees. However, it may be necessary to fell a tree. If
heavy equipment is working in the area, it may be used to fell the tree; if not, a chain saw may be used.
If a chain saw is not available, use an ax.