encountered when setting a monument, it is impossible to address them all. The ultimate selection of the
site is at the discretion of the monument setter.
(2) Temporary monumenters are the same as permanent monuments except that the required
preservation time is less. Temporary monumenters consist of a 1-by 2-inch wooden hub (or larger) with
adjacent guard stakes, a copper nail and washer, or a temporary spike that is set in relatively stable
material.
b. Monument's are susceptible to damage or destruction. It is necessary to anticipate any
construction that might occur in the area. Frequently, monuments that are set in asphalt surfaces are
paved over. Monuments placed off the edge of an asphalt surface stand a better chance of survival.
c. Monuments should be accessable. If the monument cannot be found or conveniently occupied,
its worth is questionable. Determine if there are nearby objects that can be used as references.
Distances and directions from prominent reference objects should be used to locate a monument. These
distances and directions are referred to as lines of position (LOPs). The prominent objects are referred
to as origins. At least two LOPs are required to describe a point. The closer to perpendicular the angle
at which the LOPs intersect, the more accurate a position can be described.
d. All monuments are subject to the effects of geologic and soil activity. Vertical-control
monuments and BMs are particularly vulnerable because this activity results in vertical movements
much more than horizontal motion. Selecting advantageous topographic features, such as on the crests
of hills where the soil consistency tends to be firm, increases soil stability and decreases frost heave.
When possible, choose a site with coarse-grained soils. Fined-grained soils (such as clays) are
susceptible to high moisture content.
e. If a monument extends below the ground, there is a chance of encountering underground cables
or pipes during installation. Evidence of underground utility lines can often be observed at the surface.
Waterlines are marked by valve boxes, and in structures newer than 1960, the utilities are likely to be
buried. Avoid digging near light poles, phone lines, or electric and gas junction boxes.
f. The ideal site provides maximum visibility above the horizon, plus 15,. Any obstruction above
15, could block satellite signals. The ideal site should have visibility in all directions above 15,;
however, an obstruction in one or two directions may not affect the ability to use the site for GPS
surveying. Existing BMs should be used as GPS monuments as often as possible. New monuments
should be located as close as possible to a known vertical control. Maximum effort should be made to
locate all GPS-type monuments within 100 feet of easy access to ground transportation.
2-50. Station Names. The customer normally assigns the station names. An example of a station name
would be the project name or number followed by the sequence number of that station in the scheme-of-
control extension. Names should
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EN0593
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