Photogrammetry and GPS for vehicle positioning aimed at underground utiliy survey

Abstract

The surveying of underground utilities in urban areas is usually performed using geophysical techniques such as GPR (acronym of Ground Penetrating Radar). Nevertheless, this instrument is not able to position itself autonomously and it must be coupled with a navigation device. In the last years, the need to georeference the georadar, even in urban environment, drove to the proposal of a positioning approach that use Photogrammetry, using some Ground Control Points extracted from urban maps as constraints. The feasibility of this methodology has been confirmed from some tests, previously carried out. In this paper, the results of a test realized in the city of Cremona, applying an inverse photogrammetric approach, are presented. During data processing, some different choices of Ground Control Point distribution for georeferencing the photogrammetric block (i.e. only GCPs extracted from digital maps or with the addition of some GPS points too) are analyzed. The effects of the introduction of additional constraints, like relative orientation between the two cameras used during the survey, are studied too.