INSTALLATION OF MONITORING STATIONS - Wind Resource Assessment: A Practical Guide to Developing a Wind Project - page 65

guy anchor at each corner may be 50 m (164 ft) from the base. Thus, in this example,
the four anchor points form a square of roughly 71 m (233 ft) on a side. When the
tower is lying flat, it extends about 10 m (33 ft)—plus the length of any lightning
mast or vertical sensor boom—beyond one of the outermost anchors. This creates a
kite-shaped footprint, with two sides of 71 m and two sides of at least 80 m (Fig. 5-2).
It is recommended that the guy anchors be located at four of the eight primary
directions with respect to true north (i.e., N, S, E, W or NE, SE, SW, NW), as
indicated by bearing reference stakes, and that one of these directions be aligned as
closely as possible with the prevailing wind direction. The advantages of this strategy
are, first, it is easy to verify the orientations of the sensor booms by taking a bearing
from the prone mast, and second, raising the tower into (or lowering it away from)
the prevailing wind direction offers a welcome degree of stability by maintaining the
lifting guy wires in constant tension. Raising or lowering the tower during periods of
high winds or gusts should not be attempted under any circumstances.
The tower is normally raised using a gin pole and winch-and-pulley system (Fig.
5-3). The choice of anchor for both the lifting/lowering station (where the gin pole
is attached to the ground) and guy wires is critical. Anchors are most often driven
into the soil (Fig. 5-4), but whether this is feasible and the type of anchor that should

~80 m

Tower height 60 m
(when laid down)

Cleared area
(minimum, shaded)

50 m

To w e r

Gin pole

Lifting
station
anchors

Outer anchor
radius is 50 m

~71 m

Figure 5-2. The diagram illustrates the footprint of a tilt-up tower. In this example, the prevail-
ing wind direction is assumed to be from the southwest. The “X” marks indicate anchor points.
The orange dashes represent the guy wires as the tower is being raised, and the black lines
indicate the path of the guy wires when the tower is fully erected. Source: AWS Truepower.