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A small boat hydro survey for a big boat's requirements
A 327Kb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE
The recent arrival in Bridgetown, Barbados of the massive Cunard flagship Queen Mary II caused a minor parking problem. With a length of 345m (1,132 ft) and a draft of 9.7m (31.82 ft), there is now a need to investigate the further dredging of an extended docking area that could be used as an auxiliary haven for smaller cruise ships. A recent hydrographic survey by Hart, Hutchinson & Field (HHF), a local Barbados survey firm, was used to chart depths to ascertain the feasability of extending the dredging to the area currently used as a grain terminal. If made deeper, this basin could then be used for overflow berthing of cruise ships when required.
The survey firm is actively involved with projects throughout some twenty islands within the Caribbean. One of the technical requirements that was clearly identified in the early development of HHF's business was the need for truly portable hydrographic survey equipment that could be easily transported by light passenger aircraft or by local ships to sites within the Islands.
The portable system used for the Bridgetown survey consisted of an Ohmex SonarMite Bluetooth echo sounder with software, a Trimble Recon PocketPC data logger, Ashtech Z surveyor rover, an Ashtech static base station, and last but not least, a shallow draft boat nicknamed Poco Loco that could easily maneuver within the berth areas. This was particularly useful as the survey quickly detected areas of dredging that were missed by the contractor.
Ohmex's portable SonarMite echo sounder is based on their WinSTRUMENT concept; it uses the latest portable computers integrated with new measurement technologies using Bluetooth communications. Because the use of wireless technology enables the instrument to be waterproof, it can be used in a "hostile" environment, while the more sensitive computer features can be located in a more "computer friendly" environment up to 50m away from the instrument. In this case the computer used was the Recon unit which was ruggedized for survey use in any situation. A new feature of the SonarMite is the inclusion of a six axis solid-state accelerometer with calculated output of integrated Heave, Pitch and Roll measurements.
The datalogger used was the Trimble Recon, a rugged PocketPC handheld designed for the harsh hydrographic fieldwork. It comes with Microsoft PocketPC 2003 software, an all-day battery with easy to change cartridge, two Compact Flash slots for multiple card formats, a standard D9 serial port, and Bluetooth connectivity provided by a standard SD card.
The technology used in the Recon display is a combination of "transmissive" and "reflective" LCD technology. With a transmissive device, an electronic substrate emits a fluorescent white 'backlight' passing through the LCD to enable it to be seen by a viewer. This is the form used by most PC displays making them ideal for viewing indoors or under low light levels. A reflective display enables light (such as daylight) to pass into the LCD and be reflected back from a passive substrate. Ideal for outdoor use, these devices consume very little power. Their visibility performance is in proportion to the available light. By using a combination of these two technologies the new types of computers designed for field use can be used in most light conditions. A flaw that was recently observed during the Bridgetown survey was that the backlight tends to be either on or off; in the situation of following hydro survey lines it was found that the display went from sunlight to shade during the critical time of swinging the boat around, making it difficult to view the current depth parameter. It was also noted that it was difficult to detect if the backlight was currently on in strong sunlight conditions. Apart from the increased power consumption, this also resulted in a 'flickering' effect on the display. A suggestion made to the manufacturer was that they consider a simple light sensor to vary the backlight according to ambient light.
The software used on the Recon was the PocketPC version of the SonarMite program from Ohmex. This software performs the functions of capturing, displaying and saving data from both the echo sounder and the GPS. All data is color coded by depth so both the tracking plot and the echo datagram provide real feedback on the depth and coverage of the survey.
One of the typical quality control functions of a hydrographic survey is to preform a "Barcheck" to check the calibration and performance of the echo sounder. This routine is simplified using the SonarMite together with `event marker' facilities within the WinCE software. The user can easily raise and lower the checking plate as a numeric check also moving the plate in and out of the echo sounder beam as a functional test using the event marks for later reference.
New features recently added to the PocketPC version of the SonarMite software include the addition of waypoints and events. The waypoints can be either loaded from a file of XY coordinates providing a simple reference frame to help follow survey lines on screen, or as a waypoint event that is stored at the current location to provide a marker or return reference point. Similarly numbered events can be entered to provide reference points in the stored data set, the most common use of these being associated with "Barchecking" procedures to calibrate the echo sounder.
As HHF's team of early technology adopters have quickly found, using equipment like the SonarMite, connected by Bluetooth, gives the advantages of the seamless integration between Windows CE and Windows XP processing software.
Gregory Hutchinson's experience in all aspects of land surveying has involved many projects throughout the Carribean islands and the United Kingdom. Licensed since 1982, he is currently a shareholder and director of Hart, Hutchinson & Field Land Surveying and Development (HHF Inc) on the island of Barbados.
A 327Kb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE
Editorial: CGSIC in Savannah
The 48th meeting of the Civil GPS Service Interface Committee (CGSIC) was held September 15-16, 2008 in Savannah, Georgia. Of particular note was the announcement that NDGPS will continue. Funding is still a challenge, but the powers that be have decided that NDGPS, like GPS, is .... Read the Article
Point to Point: Relatively Speaking
Sooner or later it happens: one of your friends or relatives asks you to survey their property, or otherwise act professionally on their behalf. Is that all right or do we have a higher obligation to the public concerning impartiality? Although I have not conducted an exhaustive examination of the .... Read the Article
More Than a Simulation
When work such as land surveying requires precision and gets impacted by changing technology, it makes sense to be introduced to high-tech equipment on an actual project rather than on a simulation exercise or in a classroom setting. That runs counter to ... Read the Article
Optech Incorporated: The Lidar Company
In the early 70s, Dr. Allan Carswell, a physics professor at York University in Toronto, developed a pulsed laser system used in the world's first lidar bathymetric mapping system. Based on his research, Carswell founded Optech Incorporated in ... Read the Article
The Wow Factor: SmartWorx from Leica Geosystems
Every version of Leica Geosystems software contains user requested features. The latest product request that made the final cut was a "Field to Office" application. This full-featured FTP and transfer software is now built into the operating system of all System 1200 sensors, making it possible for .... Read the Article
Visualizing N G S Control Stations in Google Earth
Google Earth is rapidly becoming the land surveyor's tool-of-choice for preliminary job site reconnaissance and survey planning (see "Topography is Dead," by Joel Leininger, March 2007). Survey projects often begin with the investigation and .... Read the Article
Surv-Fi, Part 2: Boomer's Hearing
Stand back from the cradle Hector!" Vel warned her colleague. "You could receive a rather nasty static shock as it spins up!" Hector Fontecilla stood shivering in the still Chilean Patagonia morning awaiting instructions from Vel Kawashima. Ten thousand ... Read the Article
Tips & Tricks: Hidden Point Offset
Let's say it's 5:30 Friday afternoon and you're past ready to call it a week. You've just calculated the angle and distance to look for one of the last monuments you need to tie in. You turn the instrument to the angle and shoot a distance that measures just behind a tall tree. After a few minutes' search ... Read the Article
FeedBack
Wendy, quite possibly the best article ever written in a surveyor's journal ["If Not Now, When? Sept. 2008]. It matters not how technically proficient we are, how much money we make or how well "esteemed" we seem to be in our profession when we face serious illness or death. What do our friends and ... Read the Article
Vantage Point: Diversions in the Park
There is not a lot of unused land in our urban and increasingly suburban areas. It disappears under shopping centers and houses and roadways at a rate unimaginable a century ago. So it may not be unusual to start eyeing land that was set aside for parks and open space at ... Read the Article
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