Figure Commands

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 surveyors 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 BCs, 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 Figures 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 points 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.

This page last edited on Thursday, June 03, 2010