Extraction of characteristic points from radar image. Ekstrakcja punktów charakterystycznych z obrazu radarowego

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Maksymilian Cybulski
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1 Sientii Journls Mritime University o Szzein Zeszyty Nuowe Ademi Mors w Szzeinie 008, 13(85 pp , 13(85 s Extrtion o hrteristi points rom rdr ime Estrj puntów hrterystyznyh z obrzu rdroweo Tomsz Przy Ademi Mrynri Wojennej, nstytut Morsih Systemów Rdioeletroniznyh Gdyni, ul. Śmidowiz 69, tel , e-mil: t.przy@mw.dyni.pl Key words: rdr nvition, extrtion Abstrt The problem o ontinuous position vilbility is one o the most importnt issues onneted with humn tivity t se. Beuse the vilbility o the eletroni nvitionl systems n be limited in some ses (or exmple durin militry opertions we should onsider dditionl methods o therin inormtion bout ship's position. n this pper, one o these methods is presented, whih is bsed on extrtion o speii etures rom rdr imes hrteristi points o the ostline. Słow luzowe: nwij rdrow, estrj Abstrt Ciął dostępność pozyji jest jednym z njwżniejszyh problemów związnyh z ludzą dziłlnośią n morzu. Poniewż dostępność eletroniznyh systemów nwiyjnyh może być ornizon w nietóryh przypdh (np. podzs operji wojsowyh, powinno się rozwżyć dodtowe metody romdzeni inormji o pozyji sttu. Jedn z tyh metod, oprt n wybierniu onretnyh elementów z obrzów rdrowyh punty hrterystyzne lini brzeowej, zostł zprezentown w niniejszym rtyule. ntrodution The primry positionin system n be unplued, destroyed or mluntionin. This is the reson why lterntive methods o position estimtin should be ten into ount. This is espeilly importnt or nvl ships. The militry uxiliry positionin system should be s utonomous s possible. t should ive the possibility o ship's position ixin without inormtion rom eletroni nvitionl systems lie GPS or others. Rdr nvition perormed in n utomti wy hs suh eture. n the pper, one element o utomti rdr nvition system, nmely hrteristi points extrtion subsystem, is presented. Funtionin o the system Hypothetil struture o the whole system is presented in iure 1. The min ts o the rdr imes reistrtion subsystem is trnserrin rdr sinl to the diitl orm [1]. The dditionl ts is elimintion o ehoes omin rom movin ships. n this se, the subsystem should be ble to tr imes omin rom rdr in order to distinuish the onstnt objets rom the movin ones. The min ts o the hrteristi points extrtion subsystem is preprin vetor o hrteristi points visible on the reistered rdr ime. The min ts o hrteristi points identiition subsystem is identiyin the suiient number o previously extrted points to lulte ship's position. n the inl step, the system estimtes ship's position usin identiied points nd trditionl nvitionl methods. The method o extrtion o hrteristi points rom rdr ime When tlin bout the extrtion o hrteristi points rom rdr ime, we should strt with presentin onsidered imes in the orm o ontour invrint. First, we should deine the ime L (x, y [, 3]: 74 Sientii Journls 13(85

2 Extrtion o hrteristi points rom rdr ime Rdr Rdr ime Rdr imes reistrtion Rdr ime Chrteristi points extrtion Points vetor Chrteristi points identiition Coordintes o points Positionin Fi. 1. Struture o the system Rys. 1. Strutur systemu L : O R where: O set o points P (x, y: {( x, y R : x < 0, N >, y < 0 > } O =, M N, M N determine the size o the ime. We my determine the diitl ime s untion L (n, m: L :O where O O is set o points P i (n, m, i = 0,1,..,N*M 1: {( n,m Ν :n < 0,N >,m < > } O = 0,M Let us ssume tht N nd M whih determine the size o the ime re odd, so or every ime we n determine the entrl point P o (n o, m o : N 1 M 1 no =, mo = The nloue ime s well s the diitl one n be presented in polr oordinte system. For tht presenttion every point P(x, y is determined by berin on tht point rom entrl one nd distne d = P o P [3]. There is possibility to hne the representtion rom the polr oordinte system to the Crtesin oordinte system. A mppin untion rom Crtesin to the polr oordintion system nd vie vers re presented below (or the nloue ime: Ν x = ( x, y, d = ( x y d, (, d, y = (, d, x y O x =, y As or the diitl ime, we should strt with determintion o the mppin o eh point o n nloue ime to the pproprite point o diitl ime. P P : O O ( P = r min P P P O Finlly, we et the mppin untion between polr nd Crtesin oordinte system or the diitl ime: ( ( n, m = (, d, ( d P x y, The next step is determintion o the set o points lyin on the berin, i.e. O nd O {( x, y O : ( x y } =, = {( n, m O : ( n, m = ( P P } =, Next we deine the set, W o visible points o diitl ime lyin on the berin. P { P : L ( P 0}, W = > Zeszyty Nuowe 13(85 75

3 Finlly, we n deine the untion on ontour d = : invrint ( o ( min P P = (1 P, W n order to simpliy the lorithm o hrteristi points extrtion, untion (1 hs been repled by untion: o ( = min P P, = 0,1,..,( N + M 1 P, W where ( P Tomsz Przy ( = b, is the berin t ostl point o the ime ( P = {( n, m : n = N m M} b, b = nd is n index o the ostl point in the ordered series o ostl points. The orderin untion n be presented s ollows: b b, + 1 P ( P ( n, m + 1 ( n + 1, m ( n, m 1 ( n 1, m = n = 0, m 0 = b 0 b, = 0 = or = 0,1,.., M 1 or = M,.., M + N 1 or = M + N,..,M + N 1 or = M + N,..,( M + N 1 For the untion determinin ontour invrint or the diitl ime we n deine untion ( x determined on the set { x R : x < 0,( N + M > } = 1 = then ( x ( x = or. This untion deines ontour invrint or the nloue ime. The proposed method o hrteristi points rom rdr ime extrtion is bsed on the nlysis o. As n estimtor o this untion we my use the ollowin [4, 5]: the seond derivtive o the untion ( x d Fi.. Contour invrint o the smple rdr ime ( nd rph o or σ = 0.1 (b, σ = 1 ( nd σ = 10 (d Rys.. Konturowy rint przyłdoweo obrzu rdroweo ( i wyres dl σ = 0,1 (b, σ = 1 ( i σ = 10 (d 76 Sientii Journls 13(85

4 Extrtion o hrteristi points rom rdr ime ( N + M 1, = = 0 ( N + 1 ( x σ ϕ ( x σ = 0 ϕ ( ϕ ( x, σ ( x, σ ( x, = e σ b Fi. 3. Grph o z( or σ = 0.1 (, σ = 1 (b nd σ = 10 ( Rys. 3. Wyres z( dl σ = 0,1 (, σ = 1 (b i σ = 10 ( Fi. 4. Oriinl ime (, hrteristi points lulted or σ = 0.1, λ = 0.01 (b, σ = 0.1, λ = 0.5 (, σ = 1, λ = 0.1, (d, σ = 1, λ = 0.5 (e nd or σ = 10, λ = 0.01 ( Rys. 4. Obrz pierwotny (, punty hrterystyzne oblizone dl σ = 0,1, λ = 0,01 (b, σ = 0,1, λ = 0,5 (, σ = 1, λ = 0,1, (d, σ = 1, λ = 0,5 (e i dl σ = 10, λ = 0,01 ( The seond derivtive o tht untion is s ollows: d z( x, σ = d x The lorithm should be ble to ix z( or deinite σ in points = 0,1,..,(N+M 1 nd then to ind, tht meets the reltion shown below: z ( > λ z( > z( 1 z( z( + 1, (,, P ( ( ( ( x where λ llows seretion o the set o potentil hrteristi points in the roups: visible z( > λ nd hrdly visible z( λ. Another prmeter o the lorithm is σ. We n sy tht λ elimintes hrdly visible points rom the list o hrteristi points nd σ prevents enertin them. Finlly points: n, m =,, ( ( y ( ( ( ( P x y, re onsidered s hrteristi points o the iven rdr ime. b Zeszyty Nuowe 13(85 77

5 Tomsz Przy emonstrtion worin results o proposed lorithm re presented in iures 4. Conlusions We my drw the ollowin onlusion: it is possible to pply presented lorithm to the ts o hrteristi points extrtion rom rdr ime. The onduted tests hve reveled tht the ey prmeters re σ nd λ. σ > 1, then lorithm brins hrteristi points in one point very lose to eh other or moves ost line points to the wron ples. Thus, we hve deided tht vlue o tht prmeter should be pproximtely 0.1. The presented lorithm my extrt hrteristi points or be onsidered only s n uxiliry system or n opertor, who inlly determines the lotion o hrteristi points, let s sy, by hnd. This onerns sitution when n objet hs very lre eho, nd the lorithm n estimte it s lre objet with reter number o hrteristi points. Another element o the system, whih n eliminte dditionl, improprite points enerted by extrtin points subsystem, exept the user, is the identiition subsystem. t should be ble to hoose only those points s bse points tht hve their ptterns in the bse o nowlede nd then orret their positions on the rdr ime. Reerenes 1. TAEUSEWCZ R., FLESŃSK M.: Rozpoznnie obrzów. PWN, Wrszw KUCHAREW G.: Przetwrznie i nliz obrzów yrowyh. Politehni Szzeińs, Szzein WĄŻ M.: Metod wyznzni pozyji orętu z pomoą porównni obrzu rdroweo z mpą morsą. Rozprw dotors AMW, Gdyni PRACZYK T.: Sieć GRNN w ompresji obrzów rdrowyh. Zeszyty Nuowe AMW 003, STATECZNY A., PRACZYK T.: Sztuzne siei neuronowe w rozpoznwniu obietów morsih. Gdńsie Towrzystwo Nuowe, Gdńs 00. Reenzent: pro. dr hb. inż. Andrzej Sttezny Ademi Mors w Szzeinie 78 Sientii Journls 13(85

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