I have noted many times in past articles, the advantages of using machine control on a project over traditional survey and construction layout methods for grading a project site.  I don’t believe you can reasonably argue the fact that machine control, when properly utilized, will make the construction process quicker, more efficient, more accurate and more cost effective.

Many contractors are making the switch to machine control because they understand they can bring their site to grade faster and more efficiently than they could with traditional methods.  They also believe there will be a cost savings since they won’t need surveying or construction layout for the majority of their project.  Hopefully, by now contractors realize they should still rely on land surveyors to at least set project control and perform their site calibrations to ensure the project is correctly tied into the project datums. 

But once a contractor has made the switch to machine control they should realize that there are other advantages to having machine control technology on a project site.  One of the areas where contractors will most likely see improvement is grade control or grade management.  Obviously they should see improvement in the amount of time it takes to bring a site to grade, but along with that comes better management tools.  How can machine control not only bring a site to grade quicker, but also make grade management more efficient?

One of the most important facts that land surveyors may not realize about contractors is the fact that contractors want to know exactly where they stand on a project at all times.  This means they want to know how much dirt was excavated and how much embankment was placed on a project each day.  Since many contractors use a daily quantities to bid projects, they want to know if the are meeting that quantity each and every day.  If they are coming up short, they need to know so they can add additional equipment or get different equipment and personnel in place to meet their daily quantities.  If they are moving more than they expected, they want to know so they can adjust their schedules to account for the decrease in their scheduled time.  They continually monitor their quantities to ensure they meeting their goals and also to help keep track of their production for future bidding. 

In the past, contractors primarily monitored their progress with load counts.  They continually monitor how much each piece of equipment is supposed to carry and how many trips are made each day.  However, this is only a rough estimate.  This does not account for the fact that some loads are heavy and others are light.  Many times it does not account for the dirt that is cut or pushed by a dozer, since push dirt is difficult to monitor.  It does not account for compaction of material when the embankment is place and it certainly does not account for the fact that people make mistakes when counting loads.

When a contractor sets up a project for machine control, they almost always have a surveyor, or grade checker that walks around with a rover and monitors the grade.  At the end of the day, this person can usually do a quick topo of the area that was worked on each day and run a simple volume calculation routine in the data collector software and come up with a quantity of material that was excavated or placed each day that is quite accurate.  With this system, the contractor knows almost exactly how much material was moved and where they stand on their overall quantities at the end of each day. 

The use of machine control and its related tools will allow a contractor to be more accurate with their quantities.  I have found that when contractors have more accurate information to work with, they become more particular about their quantities and more concerned about making sure they stay on track of their quantities.  This in turn requires the contractor to start off a project with the most accurate information possible. 

Most of the projects I am involved with, either I do a topo verification of project site to ensure the existing ground design surface is accurate, or in some cases we do a complete independent topographic survey of the site before construction begins.  Obviously when you are trying to maintain accurate quantities throughout a project, you need to start with accurate information.  In the past, many contractors would check benchmarks and various structures and assume that if there was no issue with those items, the rest of the site is fine. 

Now, with the technology that is available, may contactors will take the extra time to do a preconstruction topographic survey to make sure they are working with accurate information. This step is sometimes referred to as “bid verification.”  On some projects, I personally perform  the topo verification.  On other projects, the contractor does the field work and sends the data to me, and I do the office work and calculations to verify the existing surface is accurate or if there is a difference exactly what that difference is. 

I have worked on many projects where the existing ground surface in the design plans was not accurate.  As land surveyors know, these are typical issues we deal with when starting a project.  In many cases, a portion of the site was accurate, but other areas were not.  Often, it is when the existing ground information was taken from aerial photography and there was significant tree cover or tall grass that made the extraction of the true ground elevations difficult.  In other situations, the existing ground was information was just inaccurate. 

However, this is where taking the time and spending the money to do a preconstruction topographic survey of the site and acquiring accurate base information can pay dividends for a contractor.  In most cases the contractor was already awarded the project so they have already submitted their price to complete the project.  If the contractor can show that their bid was based on inaccurate quantities due to an inaccurate existing ground surface in the design plans, they can usually get a change order or a contract modification for the difference in volumes.  This is where tracking accurate volumes is crucial to prove there was a greater volume of dirt moved and more work was completed than was shown in the design plans. 

Fortunately for land surveyors, in many cases, the contractor will need an independent land surveyor to monitor and certify the quantities.  This is just one more way for land surveyors to stay involved with machine control construction projects and show that our expertise is an added value to a project and not just an additional cost. 

Machine control is typical to any piece of equipment that a contractor or a land survey may own.  Once it is in the tool box, you will find many uses for that tool besides its original intended use.  Machine control will allow you to work faster, but when used properly, it can help you manage your project better and it also allows you to work smarter. 

Grade Management Systems to consider:

Trimble Site Positioning Systems

Carlson Grade Supervisor

Topcon Pocket 3D

Leica Site Foreman