GOMACO Smoothness Indicator

GSI® GOMACO Smoothness Indicator


GOMACO Smoothness Indicator

Paver-Mounted GSI


GOMACO Smoothness Indicator

GSI Machine




GOMACO's Non-Contact Profiler
Paver-Mounted, Work Bridge-Mounted or the GSI Machine



What is the GSI?

• A non-contact surface smoothness instrument that is so versatile it provides multi-application usage.

• The GSI includes: GSI computer assembly, real-time graphic display,

media storage card, two sonic sensors, slope sensor, distance counter wheel assembly, and cables.



How is it done?

• Three different sensors, two sonic and one slope, read the smoothness data in the wheel tracks (or anywhere on the surface of the slab) on up to eight traces or four lanes in one pass. The readings are from a six inch (152 mm) footprint to simulate the true picture of the tire contact area on the pavement. The information gathered by the sensors in each trace establishes a measurement of the slab.


What can the GSI do?

• Provides immediate data to make on-the-go adjustments, if necessary, to assure maximum smoothness results.

• Gives immediate graphic display as to smoothness of the surface.

• Locates irregularities (localized roughness) in the slab that need to be corrected and records that location through the use of a distance tracking encoder.

• Concrete surface can be repaired while still in the plastic state.

• Can read multiple traces simultaneously with the addition of more instruments.

• Smoothness readings can be seen before saw cuts are made for joints and tining or the texturing of the slab.

• Data gathered is used to produce commercially known profilograph indexes.

• Printout of surface smoothness includes station or footage reference from starting station, job information, bump location, and profile index numbers.



What additional features does the GSI machine have available?

• The GSI machine can be used to check the accuracy of stringline setup before the actual paving takes place.

• Checks accuracy of the sub-grade to obtain maximum yields and determines potential smoothness of the final slab before paving (based on the sub-grade).

• Provides the ability to study the smoothness of the slab during the curing process for future research on mix designs.

• The GSI machine's automated steering capability guarantees the highest repeatability and accuracy in the industry.



Who would want to use the GSI?

• Paving contractors
• Flat floor slab contractors
• Consulting engineering firms
• DOT (Department of Transportation)
• Federal highway authorities




GOMACO GSI (GOMACO Smoothness Indicator) For On-The-Go Concrete Smoothness Information
2 minutes 6 seconds







GOMACO Smoothness Indicator graphic




In today's competitive concrete paving market, with increasingly stringent rideability requirements, GOMACO offers a tool to help you achieve maximum paving results... the GOMACO Smoothness Indicator (GSI®).


GOMACO Smoothness Indicator

GOMACO Smoothness Indicator


The GSI, operating as paver-mounted, work bridge-mounted, or the independent GSI machine, has the ability to monitor and report your smoothness readings to you instantly. It's the ultimate quality-assurance tool available on the market today.

The GSI has the ability to read up to eight traces in a single pass, directly behind the paver. The real-time information collected creates the GSI number, or an instant rolling average of the surface smoothness readings. The GSI number is relative to the IRI (International Roughnesss Index) number, but created within a much shorter paved distance. That distance can be adjusted by the operator. Along with the GSI number, two other indexes are also calculated continually, the PI or profile index, which is based on the California profilograph, and the IRI. The information can also be exported as an .erd file. The indexes are derived from the true profile of the surface, determined by the data collected. These indexes are viewed and monitored on the GSI's seven inch (178 mm) diagonal, touch-screen monitor. The touch screen, with adjustable mount, allows optimum viewing.

The on-the-go surface smoothness information includes station and footage documentation for later reference of bump and smoothness locations. The GSI's bump alarm can be set with project parameters. If a bump, localized roughness, occurs during paving that is out of parameter, a bump warning is displayed and the bump's station location is marked on the graph for exact reference.

The GSI's feedback allows on-the-go adjustments to fine-tune the paving operation. You instantly know how changes to a number of different paving variables directly affect the quality of your ride. Instant results eliminate having to wait until the cured concrete has been profilographed, to see how the ride has been affected by the variables.




Screen shots taken during the paving process illustrate the many different screens and the variety of information available, at the touch of a fingertip, on the GSI's touch-screen display.


GOMACO Smoothness Indicator

Part of calibrating the system is entering job-site information into the GSI's computer.




GOMACO Smoothness Indicator

Two different sensor traces can be displayed on the computer's screen at a time.




GOMACO Smoothness Indicator

A trace shows how this section of roadway did using the two-tenths blanking band.




GOMACO Smoothness Indicator

This stretch of roadway posted some good numbers on the IRI index.




GOMACO Smoothness Indicator

The GSI provides ride numbers for three different indexes with this set-up screen.




GOMACO Smoothness Indicator

Sensor positioning has to be measured out so the GSI computer knows what it's measuring.




Paver-Mounted GSI –

GOMACO Smoothness Indicator

Immediate smoothness readings are available with the GSI on-board your paver. The paver-mounted GSI is a cost-effective quality control tool that is quick and easy to install on your GOMACO paver. Since it's on-board the paver, any interference with the rest of the paving train or finishing crew is minimal. It also has the capability of reading multiple traces, from one to eight.

GOMACO is experiencing an increased demand for the paver-mounted GSI as a tool for checking rideability on-the-go.

The effectiveness and quality of the GSI has been verified by contractors on projects around the world and by independent studies. The GSI recently completed a three phase research project by The Strategic Highway Research Program (SHRP2) for the Transportation Board of the National Academies. The study, in phase one, set out to identify real-time smoothness measuring technologies for concrete paving. Phase two and three consisted of field demonstrations and evaluations.

GOMACO Smoothness Indicator


The following are some published observations and results on how well the GSI performed in the study...

The consensus among the contractors was that the GSI's real-time smoothness measuring technology represents a valuable quality control tool. Examples of intentional process changes that can be evaluated include:

• Equipment adjustments
-Paver speed
-Vibrator frequency
-Sensitivity of paver evaluation controls
-Oscillating correcting beam frequency
-Numerous others

• Process changes
-Concrete workability
-Concrete dumping/spreading procedures
-Stringline tension
-Hand finishing techniques
-Mixing time
-Stopping the paver vs. slowing the paver
-Numerous others

The report also goes on to say that the GSI is also a powerful diagnostic tool; similar to equipment used by automotive technicians to identify needed auto repairs. The current state of practice is to cautiously make an equipment/process change and wait approximately 24 hours for feedback when the hardened pavement can be profiled. With the GSI, the process becomes instant.


On a paving project in Alabama, a GOMACO contractor equipped their two-track GP-2600 with two paver-mounted GSI units. Strict ride specifications allowed no room for error, so they spent three days fine-tuning their paver and their paving processes. Changes were tracked on the GSI's Event Log, which allows important events such as sensitivity changes, draft changes and more to be marked on a graph. The entire list of marked changes can be reviewed. Then, the instant feedback from the GSI showed them what each change was doing to their concrete. They knew right away if the change had improved their quality or hurt it. No 24-hour wait was involved before a profilograph could be run on the new concrete roadway.




GSI ToolsTM– Grade Analysis

GOMACO Smoothness Indicator

A GSI trace over a prepared grade for paving can provide a complete grade analysis with our GSITools software. This software provides a cut and fill report for final grade preparation and can build a profile of the grade to estimate the concrete yield of the project.

The following is an overview of the Grade Analysis Tool features:

• Grade Analysis Report
Selected profiles | Trace details | Slab volume | Project parameters | Grade cut/fill summary | User selected graphs

• Project Trace Selection
Add/delete reference (stringline or stringless) traces | Add/delete wheel path traces

• Project Parameters
Slab definition | Grade cut/fill parameters | Sensor positions | Grade offsets

• Table View
Elevation data | True profile data | Grade cut/fill details | Grade cut/fill summary

• Graph View
Elevation | True profile | Grade cut/fill details




GOMACO Smoothness Indicator

GOMACO Smoothness Indicator



GSI – Survey Tool

GOMACO Smoothness Indicator

With the GSI Survey Tool, a GSI trace over an existing roadway can provide data for a 3D model in an overlay application. The GSI will collect the data with multiple traces (up to eight) in a single pass for the pave model. The GSI operates with a prism mounted to the machine and a Total Station located on a hub. This data collection provides Eastings, Northings, and Elevations for the pave model. This single pass with the GSI on a project totally eliminates the tedious handwork of two survey engineers and provides an accurate visualization of an existing roadway for a 3D model to be used for stringless paving of an overlay project.




GOMACO Smoothness Indicator




GOMACO Smoothness Indicator

The GSI, operating as paver-mounted, work bridge-mounted has the ability to monitor and report your smoothness readings to you instantly. It's the ultimate quality-assurance tool available on the market today.




GOMACO Smoothness Indicator

Two paver-mounted GSI units provide instant rideability results on Interstate 75, near Pinconning, Michigan. Three different sensors, two sonic and one slope, read the smoothness data in the wheel tracks (or anywhere on the surface of the slab) on up to eight traces or four lanes in one pass.




GOMACO Smoothness Indicator

The GSI profiles the grade with 3D stringless controls. Each trace collects the X, Y, and Z positions needed to create a true 3D map of the terrain.




GOMACO Smoothness Indicator

A paver-mounted GSI unit provides immediate monitoring to assure proper paver setup and performance or examine for corrective measures that need to be taken.




GOMACO Smoothness Indicator

Two paver-mounted GOMACO GSI units monitor the smoothness in each driving lane. The information is instantly displayed and reviewed on a single touch screen mounted on the side of the paver.




GOMACO Smoothness Indicator

The GSI took part in the Federal Highway Administration's "Profiler Round-Up" study. Sixty-eight road profilers were compared and verified on two different test tracks, one in Blacksburg, Virginia, and the other in Newville, Pennsylvania.




GOMACO Smoothness Indicator

Smoothness readings are being taken on the Atlanta, Georgia airport.




GOMACO Smoothness Indicator

The GSI display, mounted at eye level on the side of the paver, offers a variety of viewing options of the information collected by the GSI.




GOMACO Smoothness Indicator

Two paver-mounted GSI units were instrumental in helping fine tune this unbonded, 11 inch (279 mm) thick concrete overlay paving operation in Alabama.

Read more about this project in GOMACO World 39.2.




GOMACO Smoothness Indicator

The GSI in transport mode easily travels around the job site.




GOMACO Smoothness Indicator

Both sonic and slope sensors mounted to the GSI's frame take readings simultaneously to determine pavement smoothness.




GOMACO Smoothness Indicator

The GSI monitor was positioned on this paver for easy viewing of the smoothness trace from ground level or from the work bridge.




GOMACO Smoothness Indicator

Four GOMACO GSI units are mounted to the back of the paver. This provides immediate monitoring to assure proper paver setup and performance or examine for corrective measures that need to be taken.




GOMACO Smoothness Indicator

This GSI traces four wheel tracks, providing accurate data for the smoothness readings on this two-lane street.




GOMACO Smoothness Indicator

The GSI measures pavement smoothness behind the texture/cure machine on a project near Onawa, Iowa.




GOMACO Smoothness Indicator

Here, the GSI is mounted to the back of a GP-2600 and in the center of the paver. The monitor can be mounted anywhere on the paver for easy viewing.




GOMACO Smoothness Indicator

The rideability of this concrete roadway in Austin, Texas, is constantly being monitored by the GSI.

Read more about this project in GOMACO World 33.2.




GOMACO Smoothness Indicator

The GSI can commence tracing right off the morning header, ahead of the texture/cure machine. If used later, saw-cuts, rains or wetness of slab do not affect readings.



GOMACO Smoothness Indicator

A GHP-2800 paves the curve on the Martinsville Speedway in Virginia for NASCAR racing. A GSI follows the paver to check smoothness results.

Read more about this project in GOMACO World 33.1.




GOMACO Smoothness Indicator

The GSI was successfully tested for repeatability by steering from stringline. The GSI was taken off line and returned to line for retracing. Similar traces revealed excellent repeatability by the GSI.





GSI Machine Specifications:


Engine: 4024T John Deere diesel engine, 60 hp (44.8 kW), Tier 2.

Frame: Pin-connected main frame. Standard frame length is 30 ft. (9.14 m).

Automated Steering Control System: Electronic/hydraulic forward and reverse steering control system. Control panel with monitor gauges.

Hydraulic Leg Assemblies.
Four Wheel Suspension:
Hydraulically driven, all wheel steering, wheels turn 90 degrees for loading or moving the machine.

Tires: Solid rubber tires, 28 in. (711 mm) x 9 in. (229 mm) R15 in. (381 mm) wheel.

Steering: All-wheel steer.
a. Coordinated four-wheel steer (operational & transport mode)
b. Crab-steer (operational & transport mode)
c. Front-steer only (operational & transport mode)
d. Rear-steer only (operational & transport mode)
e. Counter-rotate (operational mode)
f. Stringline steer (operational mode)

GSI Computer Assembly: includes real-time graphics display, computer assembly, media storage card.

Four Wheel Track Sensor Assemblies: includes eight sonic sensors, slope sensors, mounting brackets and cables. Sensors trace the wheel tracks for reading smoothness data for two lanes.

Operators Platform: includes seat assembly.

Emergency Stop Switches.








For Additional Information


Download The GSI Brochure (PDF)

Download The GSIToolsTM Grade Analysis Tool Brochure (PDF)

Download The GOMACO Full Line Brochure (PDF)

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