Civil Engineering Reference
In-Depth Information
Caution is advised when setting up a tripod on a smooth surface, such as a con-
crete sidewalk or concrete floor. If the points on the end of the legs are unable to
penetrate the surface, there is nothing to prevent one or more of the legs from skid-
ding out, causing the instrument to come crashing down onto the ground. The steel
points also become dull after use so they are less capable of gripping the surface
and more likely to slip. Frequently replacing or sharpening the points is a good
idea. On some tripods, the leg hinge pins at the top are adjustable to increase the
friction, but this should not be relied upon to prevent the legs from skidding on a
smooth surface. Having the hinges too tight makes setting up the tripod more dif-
ficult. One option is to drill small holes into the concrete for each of the leg points.
Some tripods come with adjustable straps which attach at the bottom of each leg
so that the tree legs can be tied together, preventing them from spreading.
5.7 Setting-Up a Tripod
Knowing how to set up a tripod is one of the first things a new member of a sur-
vey crew must learn. If the survey will be made using a total station and prisms,
tripods will be used to support them. If the survey is to be made using static GPS,
a tripod will be used to support the GPS antennas. If a GPS base station is to be
used, a tripod will support the base station. Even small surveys may require many
setups so the persons setting up the tripods will need to be both accurate and effi-
cient. Where many setups are required during the course of a survey, the amount
of time expended on setting up tripods can add up to many hours. Learning how to
quickly and accurately set up a tripod will save the survey crew time and the client
money. The following paragraphs are intended primarily for those who are learn-
ing to become surveyors or those who wish to know the details of setting up a tri-
pod. Readers who do not plan to ever set up a tripod may want to skip this section.
Knowing how to set up a tripod is one of the first things a new member of a
survey crew must learn.
Setting up a tripod is not difficult, at least on relatively level terrain, if the correct
procedure is followed. Experienced surveyors each have their preferred method but
there are common steps which all surveyors tend to follow. Once a person has per-
formed many setups, they will develop a technique that works best for them. For this
explanation, we will assume that the ground is relatively level. We will also assume
that a tribrach has already been installed on the tripod. Because a total station is a
very delicate piece of equipment it should remain in its case until the tripod setup is
complete.
Never attempt to set up a tripod with an instrument in the tribrach.
Often,
when the legs are stepped on in order to force them into the ground, they will glance
