Semi-Automated Detection and Extraction of Unexploded Ordnances using the Object Based Image Analysis Approach

Transcription

1 Semi-Automted Detection nd Extrction of Unexploded Ordnnces using the Object Bsed Imge Anlysis Approch Ivn Rcetin, Andrij Krtlić b Fculty of Civil Engineering, Architecture nd Geodesy, University of Split, Croti b Senior ssistnt, Fculty of Geodesy, University of Zgreb, Croti ABSTRACT: This pper describes ppliction of methodology for semi-utomtic interprettion of digitl multisensor imges for the purpose of detection nd extrction of unexploded ordnnces developed within the EU FP7 TIRAMISU project on the site of exploded mmunition depot in Pdjene, Croti. Process relies on combining the dvntges of the both rdiometric nd object bsed imge nlysis using the sttisticl tools where lessons nd rules lerned on the test imge re then pplied on other imges of the sme scene but different loction. In this cse methodology hs been pplied on eril imges cquired by consumer DSLR cmer mounted on helicopter flying t verge height of 300 meters bove ground level. Prior to this ppliction perspective preliminry result ws chieved for luminum objects. During the further ppliction, imge processing for improved detection nd extrction of corroded objects ws defined nd evluted. Achieved results of methodology ppliction on different scenes t sme loction (exploded mmunition depot). At the end, perspective of further reserch nd nlysis of this methodology is stted. Key words: Remote sensing, Imge processing nd nlysis, OBIA, UXO 1. Introduction In September 2011 severe forest fire cused the explosion of mmunition storge depot in Pdjene, Figure 1. For ddressing these situtions, ground tems of demining experts re engged for clernce nd recovery tsks. In scope of ongoing EU FP7 TIRAMISU project n ide of reserch nd development pproch to this problem ws initited. This ide resulted in deployment of dt cquisition module of TIRAMISU Advnced Intelligence Decision Support System (T-AI DSS) multisensor imgery cquisition system (Bjic, 2010) for eril survey of wider re of mmunition storge. Density distribution of the scttered mmunition nd prts ws estimted by the Tsk force of Crotin Ministry of Defense for recovery: inside the rdius of 800 m form the mmunition storge center 70 % of the pollution ws expected, while dditionl 20 % in the rdius of 1000 m (Bjic, 2012). The results of this ctstrophe were scttered unexploded ordnnces (UXOs) vrying from rifle mmunition to the cluster bombs. Nonetheless, due to the explosion UXOs were found in vrious forms: intct, slightly or significntly deformed, burned, corroded or with the originl pint preserved.

2 Croti Figure 1 Imges of mmunition storge depot Pdjene: ) digitl orthophoto before the explosion (vilble t URL 1), b) oblique eril imge fter the explosion (vilble t URL 2) 2. Methodology b Dt used for UXO detection nd extrction t the exploded mmunition depot were eril RGB imges mde by commercil Nikon D90 cmer. Methodology used for dt processing is methodology for semi-utomtic interprettion of digitl multisensor imges for the purpose of detection nd extrction of unexploded ordnnces (Rcetin nd Krtlic, 2014), Figure 2. Process relies on combining the dvntges of the both rdiometric nd object bsed imge nlysis (OBIA) using the sttisticl tools where lessons nd rules lerned on the test imge re then pplied on other imges of the sme scene but different loction. Figure 2 Shemtic Representtion of Methodology for Semi-Automtic Interprettion of Digitl Multisensor Imges (Rcetin & Krtlic 2014)

3 3. Results nd discussion Prior to this ppliction perspective preliminry result ws chieved for luminum objects (Rcetin et l, 2014). During the further reserch, imge processing for improved detection nd extrction of corroded objects ws defined nd evluted. Thresholds for pixel vlues in every lyer (R, G, B, Principl components, Independent components) were defined for delinetion between clsses for the test imge which contined most of the UXOs found in the mmunition depot. These thresholds re not something tht is directly pplicble on ny imge; they represent more kind of guidelines to the interpreter. A simple clssifier which rnked the highest possibilities ccording to the lredy defined thresholds ws progrmmed. In the Smple column men vlues of certin segment re inserted. If the men vlue of segment in specified chnnel (Red, Green, Blue, 1st Principl Component, etc.) is occurring in the defined intervl for some clss (UXOs, Vegettion, Stone, etc.) vlue 1 is set, in opposite 0 vlue is plced. Upper nd lower threshold vlues for clss in specified chnnel re defined on the bsis of sttisticl nlysis (Rcetin nd Krtlic, 2014). Sum of row is the sum of occurrences of smple vlue in different clsses which cn be regrded s weight. Simple possibility of occurrence is clculted by dividing the one occurrence with the weight for tht chnnel. Weighted sum is the sum of these probbilities. Higher vlues of this weighted sum for specific clss indicte the greter chnce of this smple belonging to it. Tble 1 Exmple of smple clssifier, only few clsses re presented here. Men vlues of specific segment re exported from softwre supporting OBIA nd then psted in "Smple" column. Clssifier then clcultes the weighted sum of occurrences ccording to the thresholds clculted using the sttisticl nlysis. BL755 BETAB RBK SAB MR AS R100 WARHEAD STURM Smple Continer M69 OF S-24B SUM B G ICA_ ICA_ ICA_ Lb_ Lb_b Lb_L PCA_ICA_ PCA_ICA_ PCA_ICA_ PCA_ PCA_ PCA_ R W_SUM Although the exct vlues of these thresholds re hrdly rules for direct delinetion of trgeted objects, the rtios between clsses should sty preserved on whole set of imges. Between the thresholds one showed gret results nd repetbility with the exct vlue. Vlues in chnnel from

4 trnsformtion to CIELb colour spce which re higher thn 15 strongly correlte with the corroded UXOs. Exmples of chieved results re presented on following imges (Figure 3), on blck nd white imges white pixels represent object of interest. b Figure 3 ) Input RGB imge b) Result of processing 4. Conclusion Implementtion of procedures presented in this pper does not require ny specilized knowledge or proprietry softwre to be pplied. Although sttistics behind it re complex, the procedure itself is not computtionlly demnding nd it is esy to execute. This implementtion is designed to be semiutomtic, mening tht it should serve s help to the humn interpreter rther thn replcement for him. It is cler tht no mtter wht ccurcy nd relibility imge processing nd clssifiction lgorithms chieve, ground clernce tems will definitely wtch their steps insted of wlking directly to the coordintes exported from computer softwre. Concerning the future steps, potentil of object bsed imge nlysis hs not yet been exploited to its limits. Becuse of the nture of the shpe of trgets UXOs (some of them preserved their originl shpe, some suffered only minor dmge nd deformtions, while some re in completely unrecognizble form) it is difficult to set geometry vlues for clssifiction using the OBIA. Considering tht one object cn pper in different conditions (burned, corroded or with the originl pint preserved), or it cn be locted in the sun or in the shdow dditionl resources will be invested in the reserch of textures prmeters. Acknowledgement The reserch leding to these results hs received funding from the Europen Union's Seventh Frmework Progrmme under grnt greement no , project TIRAMISU. References Bjic, M., (2010): The dvnced intelligence decision support system for the ssessment of mine suspected res, Journl of ERW nd Mine Action, Jmes Mdison University, Issue 14.3, Fll 2010, pp Bjic M., (2012): Airborne wide re generl ssessment of the environment pollution due to the exploded mmunition storges, The 9th Interntionl Symposium Humnitrin demining 2012, IARP Interntionl Advnced Robotics Progrmme 24th to 26th April 2012 Sibenik, Croti, Book of Ppers, pp Rcetin I., Krtlic, A., (2014): Methodology for Semi-Automtic Interprettion of Digitl Multisensor Imges for The Purpose of Detection nd Extrction of Unexploded Ordnnces, South-Estern Europen Journl of Erth Observtion nd Geomtics 3, No2S, pp

5 Rcetin, I.; Krtlic, A.; Cndjr, Z. (2014): The concept of method for semi-utomtic interprettion within T-AI DSS, Interntionl Symposium Mine Action 2014, Book of Ppers, pp URL 1: Stte Geodetic Administrtion Geoportl, [ccessed: ] URL 2: Imge gllery of mmunition depot in Pdjene fter explosion, / [ccessed: ]