Semi - Automatic Detection of Artificial 1 Terrestrial Targets for Remotely Sensed Image

Manuscript received January 20, 2012; revised march 29, 2012; accepted April 17, 2012. 7 The authors are with the Spanish Institute for Sustainable Agriculture, CSIC, Apartado 4084, 14080-Cordoba, Spain (e8 mail: [email protected] ). 9 10 11 Abstract--Geo-referencing of remote imagery with high spatial resolution can be achieved using the 12 semi-AUtomatic GEO-referencing (AUGEO) system which is based on artificial terrestrial targets 13 (ATTs) and software AUGEO-2.0 for location and geo-referencing. The aim of this paper is to describe 14 the system and validate it. The ATTs consist of coloured hexagonal tarps 0.25 to 1.0 m in diameter, 15 placed on the ground and geo-referenced. The proposed software works as an add-on of ENVI and 16 was able to locate the ATTs (Isolated or disposed in associated couples) in remote images based on its 17 spectral band specificity. 18 To validate the AUGEO system, ATTs were placed on the ground, and remote images were taken 19 from airplanes and unmanned aerial vehicles several times throughout the year at two locations in 20 southern Spain in 2008. Three variables were considered to study ATT detection accuracy: 1) ATT 21 size, 2) ATT colour, and 3) distance between ATTs when they were coupled in pairs. The averaged 22 accuracy for the coupled 1 m red ATT (2.5 m separated) was 95.9%. As the ATT size decreased, the 23 accuracy generally decreased, regardless of the colour of the ATTs. Results from coupled analysis 24 shown that ATT detection increased as the distance between the ATTs decreased. The proposed 25 system required less time than conventional geo-referencing work, and allowed the geo-referencing of 26 images that do not contain recognisable ground control points (GCPs). This also contributed to the 27 site-specific management of agricultural plots through remote sensing, which required high spatial 28 resolution and accurate geo-referenced images. 29 30