Kelly & Shepherd is continuing to lead the civil construction sector in NSW, with its recent purchase of Topcon's mmGPS machine control technology and rover - allowing it to carry out final trim grading and dozing, as well as site survey and setup to tolerances of within 5 mm.
Topcon's mmGPS system was released earlier this year, and completely eliminates the need for staking and stringlines when carrying out final trim on pavements and subgrades.
This results in a much safer site, with no workers on the ground around heavy machinery, as well as faster, more accurate job completion.
Kelly & Shepherd has fitted mmGPS to its Cat 140H grader on November 7, and the next day it was out working on a Mirvac residential/industrial project at Regents Park, carrying out final trim and subgrade work.
It has also upgraded its Topcon Hiper+ rovers to give millimetre-accurate surveying and setout, and is using them on the Mirvac site as well.
Topcon's mmGPS technology provides a significant enhancement in the vertical measuring precision of RTK (realtime kinematics) GPS.
It incorporates new laser technology, known as "Lazer Zone", which can be combined with any Topcon RTK GPS+ system to generate vertical accuracy to within a few millimetres, compared with the centimetre accuracy of conventional RTK GPS.
Topcon's Lazer Zone technology incorporates a unique zone-beam laser transmitter, the Topcon PZL-1, which sweeps a 600 m diameter area with a 10m high "wall" of laser light.
This is in contrast to conventional lasers which emit a single beam of light, and require receivers (whether on machines or hand-held) to be in the same plane as the laser transmitter.
GPS typically gives very accurate horizontal (X and Y co-ordinates) positioning, but due to the limitations of satellite constellation geometries, cannot achieve much better than 20 mm of vertical (grade) accuracy.
However, by combining Topcon's existing GPS+ system with LazerZone, Topcon’s mmGPS delivers grade accuracies to within a few millimetres - well within the tolerances demanded by road construction authorities and other specifiers for final trim, subgrade and pavements.
In addition, stakes and stringlines are no longer required for any stage of an earthmoving and earthworks project, from initial bulk excavation to final trim.
Topcon’s GPS+ system uses both the 24 Navstar GPS satellites used by conventional GPS receivers, along with 14 Glonass Russian-owned satellites to give significantly better coverage and far fewer signal dropouts than standard GPS systems.
A compact receiver unit, the Topcon PZS-MC, fits over the top of the GPS antenna mast fitted to a dozer, grader, scraper, paver, profiler or other piece of earthmoving equipment. For surveying applications, a PZS-1 sensor can be fitted to a GPS+ Rover pole.
As one receiver can simultaneously handle data from up to four transmitters, the total effective working range is up to 2.4 km.
Whenever the receiver is within the laser zone, the laser provides vertical data to result in millimetre-accurate vertical measuring precision.
In addition to millimetre-accurate vertical measuring, the LazerZone transmitter provides faster initialisation times and better positioning reliability, with set up and adjustment able to be carried out by a single person.
A further advantage of mmGPS is that multiple GPS receivers can be used simultaneously with a single LazerZone transmitter - unlike with optical instruments, where only one measurement can be made at a time, limiting productivity.