Combining 3D GPR and Subsurface Utility Engineering to Create Accurate Utility Maps in Istanbul

A pilot project was commissioned by the Istanbul Metropolitan Municipality to assess the combined capabilities of traditional Subsurface Utility Engineering (SUE) and Ground Penetrating imaging Radar (GPiR) to accurately map and identify the utilities underneath the historic streets of Istanbul. The array based GPR technology combined with cm accuracy land surveying and advanced imaging software allows for an efficient and complete mapping of large-areas (1000’s of square-meters) with radar traces collected on a 10 cm grid. The resulting high-resolution 3D radar images are interpreted for utility lines, which are then identified and calibrated with standard SUE techniques. The combination of SUE and GPiR is a powerful technology that produces more accurate utility maps than by each method alone. The complementary technologies were successfully applied in the Eyup district of Istanbul. Typically we achieved good radar penetration down to a depth of approximately 1.5 m, after that a clay layer attenuates the radar signal significantly. The Municipality received accurate CAD drawings with the 3D location of each pipe as determined by GPiR and SUE.