Background

Technology 1: SI-SFAP (Spatial Information-Small Format Aerial Photography) SI-SFAP, specifically refers to the integrated applications of high-resolution (sub-inch) small format aerial videography/photography with commercial off-the-shelf GIS application software for highway bridge system monitoring. SI-SFAP can enhance existing inspection requirements of highway systems and provide long-term safety performance/structural performance improvements. In order to capture high-resolution aerial imaging of highway bridges and pavements at low costs, SFAP aerial photographs are typically taken from a much lower altitude (approx. 1,000 ft) such that higher resolution digital images can be captured for smaller areas. Since these photos are from a lower altitude and only small areas of coverage are needed, the orthogonal rectification of the imagery was not performed, nor deemed necessary. The resolution of the digital images is defined as the ratio of the actual physical dimension of the sensor pixel to the physical dimension of the object in the photo. The SI-SFAP technology is an integration of low-flying aerial photography, coupled with high definition video and photo recording instrumentation, onboard GPS systems, and SI-based information management systems (or, GIS) such as Google Earth ® and ArcReader ®. The integrated solution can provide sub-inch resolution photo and video imagery that allows highway engineers to manage their assets and monitor construction progress. Figure 1 shows progress of bridge construction monitored using SI-SFAP technology, which includes the use of a Cessna 210 Airplane and a Canon 5D Digital Single Lens Reflex (DSLR) camera. The aerial photos show detailed, georeferenced and time-stamped documentation of the construction project in North Carolina, including the site condition and construction progress at a resolution of 1”.

 

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Figure 1 SFAP Images of Bridge Demolition and Construction

Using SFAP, special considerations including punching shear, corner cracking, spalling, pot holes, and other damage of the bridge, can also be identified easily. Another important feature of the SFAP method is the potential of quantifying bridge relative movements by measuring expansion joint openings. Current inspection reporting does not require exact measurements of expansion joints. As a result, no documentation of bridge movements has been included in the national bridge inventory database. However, using periodic, high-resolution aerial photography such as SFAP, it is possible to establish temporal records of bridge joint movements.