Determining the floor levels of existing and re-built structures in flood prone areas is an ongoing and constant critical need. Both occupancy permits and insurance rates depend on an accurate certification of the first floor level of each structure in these zones.
In 2006, just five short years ago, I visited a prominent survey firm in Mobile, Alabama. High winds and flooding from the past hurricane season had destroyed much of the infrastructure and residences along the Florida panhandle and Mobile Bay. Reconstruction was underway.
The survey firm had many requests for floor elevation certificates related to the rebuilding of homes in outlying areas. Traditional survey methods involved carrying an elevation with a level from a established benchmark over long distances along rural roads. Not only was the methodology laborious, but the lengthy distances increased the chances for operator error in establishing an accurate elevation.
To improve the workflow, the firm installed a Topcon GPS+ reference station a few blocks from its office. The survey teams were able to get accurate elevations at remote locations using a HiPer+ GNSS rover and cellular modem communicating with the base station. The full story can be found at: http://www.topconatwork.com/PDFs/TAW_Polysurveying.pdf.
At the time, this was a revolutionary use of technology that made dramatic improvements in productivity and raised the level of confidence of survey data. Recently, Topcon’s IP-S2.1 Mobile Mapping System was used to make even greater advances for the same application.
A devastating series of floods hit Queensland, Australia in late December 2010 / January 2011. These storm events resulted in widespread evacuations, loss of lives, and paralyzed industry and transportation. Pictures of the flood conditions can be found at: http://www.cqnews.com.au/photos/galleries/flooding-emerald-town-centre/#num=6&id=flooding-emerald-town-centre
As a result of the unprecedented flooding, Rapid Survey Solutions (RSS) was contracted to perform a survey to determine the floor levels of each household in the town of Emerald. Using Topcon’s IP-S2, RSS completed the survey of 445 kilometers (277 miles) of highways, local roads, and streets in just seven days with one operator.
To meet the vertical accuracy requirements, RSS segmented the data collection runs into seven areas. A GNSS receiver was set up over an accurate permanent survey marker in each area. The data logged by the receiver was used to post-process the GNSS data collected by the IP-S2.
RSS also completed a 280 point ground control survey throughout the project area. The control points were set to an accuracy of +/- 15 millimeters. These points were then used as constraint sets for QA/QC of the IP-S2 survey data.
Complete processed datasets and a license for Topcon’s Spatial Factory software were delivered to the client, a Shire Council with jurisdiction over Emerald. The Council now has access to 360 spherical images and LiDAR point clouds of the entire area. Floor elevations of structures can be measured and a visual record of existing conditions can be analyzed. As an additional benefit, infrastructure assets can be mined from the data for management purposes.
The RSS project at Emerald is another great example of how mobile mapping systems continue to make revolutionary improvements in survey and engineering applications. We can expect even more stories like this as this emerging technology moves into the end-user mainstream.
Many thanks to Brad Chambers and Nick Nolan at RSS (http://www.rapidsurveysolutions.com.au/) for providing the details of their project.