Civil Engineering Reference
In-Depth Information
surveyors as evidence of the surveys that were performed by the original surveyor.
When performing surveys of the public lands, ield topics of the original surveys
are an integral part of these surveys and the surveyor must obtain copies of the rel-
evant ield topics when performing a survey.
Many private land survey ofices have collections of ield topics going back
many years. Because these ield topics represent valuable and irreplaceable evi-
dence of old surveys, the collections are often purchased from a retired surveyor
by other land surveyors who may be called upon to perform retracement surveys
of the original parcels, or nearby properties. Field topics also contain evidence of
boundary marker locations and ties to monuments which may help in recovering
these monuments many years later. Sometimes, a retiring surveyor or his estate
will donate or sell ield topics to a recorder's ofices or a historical society for
safekeeping and to be made available to current and future surveyors.
Digital data collection poses a potential problem for future boundary survey-
ors, and the public, because the records are, in some ways, less permanent and
more likely to be lost than ield topics. The data iles may be in a format only
readable by certain software programs which may not be available twenty years
or more later. Files may be stored on Compact Disks (CD) or Digital Video Disks
(DVD). CDs and DVDs have uncertain life expectancies, which are dependent on
factors such as type, manufacturing quality, quality of recording, handling meth-
ods and environmental conditions. Life estimates vary between 25 to 200 years.
Unfortunately, there is often no easy way to tell if a particular disk has deterio-
rated because error detection capability built into the system will correct a certain
number of errors until the point is reached when the disk is no longer readable.
Digital data collection poses a potential problem for future boundary survey-
ors, and the public, because the records are, in some ways, less permanent
and more likely to be lost than ield topics.
Even though it is time consuming, surveyors using data collection should try to
make it a habit of keeping written or printed records of all important field work. If
no permanent written and bound written records of field work are kept, there is a
likelihood that important records will disappear and not be available to future gen-
erations of boundary surveyors.
5.13 Some Common Terms Relating to Using a Surveying
Instrument
Before we discuss how angles and distances are measured we need to learn a few
terms used by surveyors which relate to the use of an instrument. The
Instrument
