Faced with the need to be mobile and ready to work at short notice on any part of the 2 km-long (1.2 mi) site,
Humphrey uses just one survey instrument—a Trimble R10 GNSS system. Using the R10 system, with either a local
RTK base station or the local Trimble VRS™ network for RTK corrections, gives Humphrey the versatility, accuracy and
reliability he needs for the array of tasks he performs. He has used Trimble VRS for all of the project’s high-accuracy
work including control, checking and verifying other contractors’ control. The L&SS base station—one of six on
the site—is used for machine control. In addition to L&SS, multiple contractors on site use Trimble equipment for
A Challenging Site
Part of the project will be built on the new land, but much of it will be built on reclaimed salt marshes. In this area, the
existing site needed to be raised by 2 m (6 ft) throughout in order to lift it above the flood plain. The required fill material
has been taken either from an old refinery site on the project or from the river during the dredging process. In both cases,
a large part of Humphrey’s work involves volumetric surveys; each survey typically calls for 1,000 points or more. It’s a
dynamic site, and delays are costly. As Humphrey moves around a stockpile, the size of the stockpile sometimes interferes
with the radio link to the base station. When this occurs, the R10 GNSS system with Trimble xFill™ technology can kick
in automatically to “fill in” the gaps, allowing him
to continue RTK surveying without interruption.
Humphrey credits the xFill technology with
keeping survey downtime to a minimum.
An additional challenge has emerged from
the area’s previous life as an oil refinery. Dotted
across the 600-hectare (1,500-acre) site are more
than 80 old petroleum tank bases, many of
which are buried. Each of these bases contains
from 600 to 1,500 piles, each with a diameter of
60 cm (2 ft). In preparation for future building
piling and construction, L&SS needs to measure
and record each pile’s elevation and position to
20 mm (0.06 ft) accuracy.
Lacking information on the locations of the tank
bases, Humphrey searched the Internet and dis-
covered an old post-war drawing of the refinery.
He overlaid this data into his design software
and adjusted it to fit an Ordnance Survey grid.
The end result was a huge boost to the search
for the tank bases, with the new drawing prov-
ing to be accurate to within a couple of meters.
Concentrating on eight of the tank bases in the
most prominent positions, Humphrey needed
to operate as quickly as possible.
To do so, Humphrey configured his system to
use Trimble SurePoint™ technology to auto-
matically record a point when the pole is plumb
and steady. This approach utilizes the system’s
eBubble, an electronic level sensor that replaces
the traditional liquid vial. The eBubble senses the
pole position and displays an electronic “bubble”
in the Trimble Access™ field software running on
Humphrey’s Trimble TSC3® controller.