Introduction
In the course of field collection of point data, there are
several codes a surveyor can use to augment his or her point
descriptions that will make life very easy on the drafter in the
office whose job it is to create the existing conditions base
map. These codes, known as “Figure Commands” in Civil 3D are a
part of the larger realm of “Field to Finish” techniques which
can single-handedly take the profitability of a survey job
through the roof.
In general, there are over 20 Figure Commands and they can be
found in the Civil 3D 2009 Help menus. A screenshot of the Help
page is found here:
In this article, we will explore three of the more popular
codes: BEG, C3, and MCS/MCE.
BEG Command
The BEG command, short for Begin, is used to begin a segment of
linework based on a description for the feature being shot. For
example, if a surveyor’s description code for the bottom of curb
is BC, the code “BEG BC” can be used to start a curb line and
have the curb line automatically drawn with a Civil 3D Figure
once the points are dumped into a Survey Database. All
subsequent points along the curb must bear the code “BC” and all
points need to be shot in order along the curb, although other
coded points may be shot intermittently between BC shots.
If another BC Figure needs to be collected, the surveyor must
either use the “END BC” command and BEGIN the new Figure or
simply use a code like BC1 or BC2. If all codes stay unique as
in the numbered BC’s, the END command need not be used. Here is
an example of the command used in an ASCII PNEZD comma-delimited
point file using the Figure code BC1:
1, (northing), (easting), (elevation), BEG BC1
2, (northing), (easting), (elevation), BC1
C3 Command
The C3 command is used to shoot a three point arc while a Figure
is being collected. The C3 code is used before the Figure’s code
and the next two similarly coded points will be the next two
points of the arc. For example, the following codes appearing in
an ASCII PNEZD point file will produce a three-point curve
within the survey Figure BC1:
1, (northing), (easting), (elevation), BEG BC1
2, (northing), (easting), (elevation), BC1
3, (northing), (easting), (elevation), C3 BC1
4, (northing), (easting), (elevation), BC1
5, (northing), (easting), (elevation), BC1
6, (northing), (easting), (elevation), BC1
More specifically, this will produce a Figure with two tangent
segments between points 1 and 3, a curve beginning at point 3
and ending at point 5, and a final tangent segment between
points 5 and 6.
MCS/MCE Command
If a three-point arc is not enough to define an arc segment or
segments in a survey Figure, then the MCS code can be used to
begin a multi-segment curve and the MCE command must be used to
end this multi-segment curve. All similarly coded points shot
between the application of these two codes will produce a series
of tangential curves within the Figure being shot.
This code may or may not be included in the description of the
actual beginning and ending points depending on the survey
equipment being used. For example, in the case of Trimble
equipment and software, the beginning and ending points are shot
with the standard code being used (such as BC1), but the
“bookend” points will have “Notes” added to them with the MCS
and MCE codes. The operations manual of each different piece of
equipment should be consulted to learn the proper use of these
codes.
Conclusion
The proper use of these codes will significantly reduce “office
time” with collected data and will help to create base maps
which are error-free and easily drawn. It will put an end to the
phone calls between office and field which serve to clarify
which points belong in the same figure and which points form
their own.
It is wrong to assume that these techniques will greatly add to
the time collecting data in the field. On the contrary, the
addition of a few letters to a point’s description will only
take an extra second or two per point but this can usually be
accomplished without additional time because the rodman is
usually walking between points for those several seconds (in a
two person system with a non-robotic gun). Even so, there is no
substitute for the accuracy and productivity gained with the
automatic creation of Figures which can then be used as
breaklines for a surface or lot lines for parcels.
Have your survey team learn the figure codes and start realizing
the huge advantage that Field to Finish codes can give your
company.
