MOBILE MAPPING SYSTEMS STATE OF THE ART AND FUTURE TRENDS. Dr. Klaus Peter Schwarz and Dr. Naser El-Sheimy

Transcription

1 MOBILE MAPPING SYSTEMS STATE OF THE ART AND FUTURE TRENDS D. Klaus Pt Schwaz and D. Nas El-Shimy Invitd Pap Dpatmnt of Gomatics Engining, Univsity of Calgay 2500 Univsity Div NW, Calgay, Alta, T2N 1N4 Canada and TS SS 3 Moil Multi-snso Systms KEY WORDS: Moil Mapping, Dict Gofncing, GPS/INS, Ral-tim mapping ABSTRACT: Digital moil mapping, th mthodology that intgats digital imaging with dict go-fncing, has dvlopd apidly ov th past fiftn yas. What usd to a topic of acadmic study has com a commcially vial industy. In this pap th majo stps in this dvlopmnt a tacd and th cunt stat of th at is viwd. This is don y looking at dvlopmnts in fou spcific aas: digital imaging, dict go-fncing, mathmatical modling, filting and smoothing. Th pap concluds with a look into th futu and th discussion of som ongoing sach at th Univsity of Calgay. 1. INTRODUCTION Th ida of moil mapping, i.. mapping fom moving vhicls, has n aound fo at last as long as photogammty has n pacticd. Th aly dvlopmnt of moil mapping systms (MMS) was, howv stictd to applications that pmittd th dtmination of th lmnts of xtio ointation fom xisting gound contol. Aout fiftn yas ago, advancs in satllit and intial tchnology mad it possil to think aout moil mapping in a diffnt way. Instad of using gound contol as fnc fo ointing th imags in spac, tajctoy and attitud of th imag platfom could now dtmind dictly. This has mad mapping indpndnt of p-stalishd gound contol. Hand in hand with this dvlopmnt wnt th chang fom analog to digital imaging tchniqus a chang that has considaly acclatd ov th past fw yas. Intgating th concpts of kinmatic tajctoy dtmination and digital imaging sultd in multisnso systms capal of acquiing, stoing, and pocssing go-fncd digital data, thus poviding a complt solution of th mapping polm with data fom only on platfom. Systms that us go-fncing and digital imaging as intgal pats will in th following considd as moil mapping systms, indpndnt of thi aa of application. Comining th advancs in digital imaging and dict gofncing has not only incasd th fficincy of moil mapping considaly, ut has also sultd in gat flxiility and low cost. In addition, it has intgatd two anchs of ou disciplin that fo too long hav gon thi spaat ways godsy and mot snsing/photogammty. In this pap, cnt dvlopmnts in moil mapping will viwd and som mging applications and futu tnds will discussd. 2. DIGITAL IMAGING In digital imaging film-asd optical snsos a placd y fully digital lcto-optical o activ lctonic snsos, oftn with multi-spctal capailitis. Ths snsos a convnintly catgoizd as fam-asd, as in th cas of digital camas, o as lin scanns, as in cas of multispctal scanns (casi, MEIS), Lida systms, o th ada-asd InSa systms. Th dvlopmnt of MMS is tid to th dvlopmnt of digital snso tchnology. This is most vidnt in th cas of famasd digital camas. Digital imaging with ths snsos is closst in concpt to aion photogammtic mapping. Thi fist us, howv, was in land-vhicl applications, not in aion applications. Th ovious ason is that in land-vhicl MMS th cama-to-ojct distancs a much small than in standad aion applications. Th poo solution of CCD chips mant that thy could not usd in aial applications without a majo loss in accuacy. Indd, th solution of CCD chips has only cntly impovd to th lvl that thy can usd in aion mapping systms, alit without yt achiving th accuacy of film-asd snsos. Th us of digital camas is advantagous caus thy liminat th quimnt to scan photogaphs. Consquntly thy sustantially duc th piod fom aw data collction to xtactd data dissmination. Digital snsos also simplify automatic point and fatu xtaction, and allow fo mo flxil data stoag possiilitis fo xampl, th imags can stod in Multi- Mdia GIS [Novak, 1993]. Although many of th cunt aial photogammtic systms a film-asd, it is xpctd that th us of film and convntional sto plotts will soon placd y fully digital camas and digital photogammtic wokstations. Today's digital camas hav som inhnt limitations and don't poduc th samsolution as film-asd camas. A standad aial photo with 40 lp/mm cosponds to x pixl. Cuntly no CCD-chips with such a solution a availal. Howv, th apid pac of digital cama volution nds th nw mdium a foc to ckond with. CCDcamas with up to 4000 x 4000 pixls, such as th Applanix DSS systm (Mostafa, 2004), a alady usd in commcial applications. Oth manufactus a dvloping systms that will plac film-asd camas, possily within th nxt ya. Oth commcial dvlopmnts a ongoing in th aa of lin scanns and includ th Lica Gosystms Aion Digital Snso (ADS40TM) and th ZI Digital Mapping Cama (DMCTM). Th ADS40TM which has n dvlopd in coopation with th DLR (Dutschs Zntum fü Luft- und

2 Raumfaht th Gman Aospac Cnt) is a th-lin pushoom scann with 28 fowad fo and 14 aft viwing angls fom th nadi. With this dsign ach ojct point is imagd 3 tims with a sto angl of up to 42. Each panchomatic viw diction includs 2 CCD-lins, ach with pixls in staggd aangmnt, lading to pixls, coving a swath of 3.75km fom a flying altitud of 3000m with a 15cm gound pixl siz. Th DMCTM has a diffnt dsign; it intgats 4 digital panchomatic camas (and 4 multispctal 3k x 2k camas) with CCD of 4Kx7K solution, sulting in imags with 8k y14k solution. With a pixl siz of 12µm x 12µm and a focal lngth of 120mm, th cama has a 43.1 y 75.4 fild of viw. A undl lock adjustmnt of a small lock with cossing flight dictions with an imag scal 1: (flying hight 1500m) sultd in a sigma0 of 2µm (1/6 pixl). At indpndnt chck points standad dviations of σ x = σ y =+/-4cm cosponding to 3.3µm in th imag (1/4 pixl) and σ z =+/-10cm cosponding to 2.7µm x-paallax w achivd (Dostl t al 2002). Such accuacy is fa yond what is achival with a film-asd cama. It should notd that although digital fam camas do cuntly not ach th accuacy of film-asd snsos, oth digital imaging tchniqus supass thm y a considal magin. Anoth impotant dvlopmnt in digital imaging is th dvlopmnt of aion hypspctal imaging snsos. Ths snsos a usd to map diffnt ands of th visil and invisil spctum. Typically thy a pushoom scanns and can poduc mo than 100 diffnt ands o channls. Th comination of spcific ands poducs a uniqu signatu fo ach matial in th scn. Ths signatus a usd to classify and idntify th matials psnt at ach location. It is thfo an xcllnt tool fo nvionmntal assssmnts, minal mapping and xploation, vgtation communitis and spcis, halth studis, and gnal land managmnt studis. This imagy is spcially powful whn comind with LIDAR points o th LIDAR gnatd sufac. Fo xampl th xtaction of fost canopy hights can accomplishd using a comination of hypspctal classification and LIDAR asd multipl tun analysis tchniqus. Among th nw tchnologis, Aion IFSAR (Intfomtic Synthtic Aptu Rada) mapping is attacting much attntion in th go-spatial community. This attntion is du to th flxiility of systm dploymnt, na wath-indpndnt opation, cloud pntating capaility, vsatil map poducts, and quick tun-aound tim. As a sult, high-solution aion IFSAR systms a poviding data to applications taditionally suppotd y convntional Photogammtic tchnology. Th th main poducts a, Digital Elvation Modls (DEMs), digital Othoctifid Rada Imags (ORRIs), and Topogaphic Lin Maps (TLMs). 3. DEVELOPMENT OF GEO-REFERENCING TECHNOLOGY Dict go-fncing is th dtmination of tim-vaial position and ointation paamts fo a moil digital imag. Th most common tchnologis usd fo this pupos today a satllit positioning y GPS and intial navigation using an Intial Masuing Unit (IMU). Although ach tchnology can in pincipl dtmin oth position and ointation, thy a usually intgatd in such a way that th GPS civ is th main position snso, whil th IMU is th main ointation snso. Th ointation accuacy of an IMU is lagly dtmind y th gyo dift ats, typically dscid y a ias (constant dift at), th shot tm ias staility, and th angl andom walk. Typically, fou classs of gyos a distinguishd accoding to thi constant dift at, namly: 1. statgic gyos ( dg/h o dg p month) 2. navigation-gad gyos ( dg/h o dg p wk) 3. tactical gyos (1-10 dg/h o dg p hou) 4. low-accuacy gyos ( dg/h o dg p scond) Only th last th classs will discussd in th following. Opational tsting of dict go-fncing statd in th aly nintis, s fo instanc Cannon and Schwaz (1990) fo aion applications, and Lapucha t al (1990) fo land-vhicl applications. Ths aly xpimnts w don y intgating diffntial GPS with a navigation-gad IMU (acclomt ias: ms-2, gyo ias: dg/h) and y including th divd coodinats and attitud (pitch, oll, and azimuth) into a photogammtic lock adjustmnt. Although GPS was not fully opational at that tim, sults otaind y using GPS in diffntial kinmatic mod w pomising nough to pusu this dvlopmnt. As GPS cam fully opational th INS/DGPS go-fncing systm was intgatd with a num of diffnt imaging snsos. Among thm w th Casi snso manufactud y Its Rsach Ltd., s Cosandi t al (1993); th MEIS of th Canada Cnt fo Rmot Snsing, s ; and a st of CCD camas, s El-Shimy and Schwaz (1993). Thus, y th nd of 1993 xpimntal systms fo moil mapping xistd fo oth aion and land vhicls. A mo dtaild ovviw of th stat of th at at that tim is givn in Schwaz t al (1993). Th volution of th gofncing tchnology duing th past dcad was du to th ongoing finmnt and miniatuization of GPS-civ hadwa and th us of low and mdium cost IMU s that cam availal in th mid-nintis. Only th latt dvlopmnt will ifly discussd h. Th intial systms usd in INS/GPS intgation in th aly nintis w pdominantly navigation-gad systms, typically stapdown systms of th ing-las typ. Whn intgatd with DGPS, thy povidd position and attitud accuacis sufficint fo all accuacy classs nvisagd at that tim. Ths systms cam, howv, with a considal pic tag (aout US $ at that tim). With th apidly falling cost of GPS-civ tchnology, th INS cam th most xpnsiv componnt of th go-fncing systm. Sinc navigation-gad accuacy was not quid fo th ulk of th low and mdium accuacy applications, th mgnc of low-cost IMU in th midnintis povidd a solution to this polm. Ths systms cam as an assmly of solid stat intial snsos with analog ad-outs and a post-compnsation accuacy of aout 10 dg/h fo gyo difts and aout 10-2 ms-2 fo acclomt iass. Pics angd twn US$ and and th us had to add th A/D potion and th navigation softwa. Systms of this kind w oviously not suitd as stand-alon navigation systms caus of thi apid position o accumulation. Howv, whn povidd with high-at position and vlocity updats fom diffntial GPS (1s psudo-ang solutions), th o gowth could kpt in ounds and th position and attitud sults fom th intgatd solution w suital fo low and mdium accuacy applications.; fo dtails on systm dsign and pfomanc, s Bäumk and Matissk (1992),

3 Lipman (1992), Bad (1993), and Knight t al (1993) among oths. With th apid impovmnt of fi optic gyo pfomanc, th snso accuacy of a num of ths systms has impovd y aout an od of magnitud (1 dg/h and 10-1ms-2) in th past fiv yas. Typical cost a aout US$ Bsid th incasd accuacy, ths systms a mo us findly and off a num of intsting options. Whn intgatd with a DGPS phas solution th sulting position and attitud a clos to what is quid fo th high-accuacy class of applications. Whn aiming at highst possil accuacy ths systms a usually quippd with a dual-antnna GPS, alignd with th fowad diction of th vhicl. This aangmnt povids gula azimuth updats to th intgatd solution and ounds th azimuth dift. This is of paticula impotanc fo flights flown at constant vlocity along staight lins, as is th cas fo photogammtic locks. Commcialization of th moil mapping systm concpt fo all application aas has n don y th Applanix Copoation (now a susidiay of Timl In gnal, th position and ointation accuacy achivd with ths systms is sufficint fo all ut th most stingnt accuacy quimnts; fo dtails s chapt 7) Duing th past fw yas a nw tchnology has apidly changd manufactuing pocsss in ngining, spcifically in snso dsign and tlcommunications. It is calld MEMS tchnology fo its poducts, which a Mico Elctonic Mchanical Systms (MEMS). Acclomts and gyos a among th aly poducts manufactud in this way. Thy a micomachind and, whn poducd in lag quantitis, will xtmly inxpnsiv. Cunt pics p snso ang fom US$ , dpnding on accuacy, ut pdictions a that thy will gt into th ang of dims ath than dollas. T Th intial snsos poducd until cntly y MEMS w fo th mass makt and w of poo quality whn compad to navigation-gad intial snsos. Gyos had constant dift ats of thousands of dgs p hou. Howv, sults cntly psntd at IEEE PLANS 2004 indicat that companis a activly woking on MEMS-asd tactical gyos, s fo instanc Hans (2004) and Gn (2004). Considing that th poduction pocsss fo MEMS intial snsos a lativly nw and that th impovmnt potntial is considal, can it xpctd that at som point in th futu th accuacy of ths snsos may sufficint to suppot navigation-typ applications? At this point it is not possil to answ this qustion in an unquivocal way. Howv, two agumnts will givn, on in favo, th oth against. Thy may hlpful fo foming an opinion. Th agumnt against is asd on som intsting mpiical sults that th authos civd y coutsy of D. Rot J. Smith at th Honywll Tchnology Cnt. Thy hav n patly poducd in Figu 1. Gyo pfomanc (masud y long-tm ias staility) is plottd vs. th nominal siz of th gyo on a log-log scal. It should notd that th figu is not asd on a comphnsiv makt analysis, ut is an in-hous study conductd y D. Smith. This is th ason why only Honywll gyos a shown. Th gyos psntd in this figu vay in tms of siz (twn 120 mm and 4 mm) and pincipl usd (RLG, ESG, HRG, FOG, 2DF oto, QRS). All, xcpt on, a poduction-typ systms. Each gyo is psntd y an llips showing th pfomanc ang in hoizontal diction and th vaiaility in siz in vtical diction. It is makal that th lin N=4 givs such a clos fit to most gyos psntd in th chat. This indicats that gyo accuacy, indpndnt of th pincipl usd, is dtmind y th siz of th snso. Th gyos aov th lin fit a typically not pssing th stat of th at, caus of oth considations (cost, liftim). Fo th on gyo low th lin, th H-ESG, which sms to outpfom th gnal tnd, only ias staility valus in a nign tmpatu nvionmnt w availal. It might thfo not dictly compaal to th oth pfomanc valus which cov a wid ang of poduction nvionmnts. Excluding ths spcial cass, th N=4 lin can considd as an mpiical law fo gyo pfomanc which is indpndnt of th pincipl usd to uild th gyo. This mans that it can usd as a pdicto fo gyo pfomanc in cass wh th siz of th gyo is givn y oth considations. Whn applying this pincipl to th MEMS gyo nvionmnt it would man that a gyo with a nominal siz of 2mm would pfom at th dg/h lvl, whil a tactical gad gyo with a pfomanc of 1-10 dg/h should hav a minimal siz of aout 20 mm. Chip siz will ssntially limit th accuacy of th IMU-on-a-chip. Similaly, th liklihood that MEMS-asd gyoscops will ach navigation-gad pfomanc is tid to th nominal siz of th gyo which has to aout 6 cm to achiv th quimnts. Figu 1: Bias Staility vs. Nominal Siz fo Matu Gyo Tchnology. Th agumnt in favo of MEMS gyo usag fo navigation-typ applications is asd on pulications cntly psntd at th IEEE PLANS 2004 and sults otaind y th Moil Multi- Snso Rsach Goup at th Univsity of Calgay, Canada. Th latt w otaind in a land-vhicl tst using a MEMSasd IMU dvlopd y mploying off-th-shlv MEMS snsos with an avag cost 20$ p snso (s Figu 2). Th tst also includd th Honywll CIMU, a navigation gad intial navigation systm, and DGPS. Both DGPS and CIMU tajctois w availal thoughout th whol tst and w usd as an accuat fnc fo th MEMS IMU sults. Intial masumnts of MEMS snsos w intgatd with th singl point positioning GPS output (accuat to m) and pocssd though th INS Tool Box (Shin and El-Shimy, 2003) Kalman filt softwa. GPS signals fom a minimum of svn satllits w availal thoughout th tst. In od to assss th pfomanc of th intgatd systm, GPS outags of 30 sconds w simulatd, y moving GPS data, along vaious potions of th tst tajctoy. Figu 3 shows th

4 positional o of th intgatd MEMS IMU and GPS duing th simulatd GPS outags. Th figu claly indicats that th IMU stand-alon sults duing th GPS outags a within 5-10 m (RMS). This accuacy mts th gnal quimnts fo ca navigation. A possil xplanation fo this supising pfomanc is th ias caliation pocdu applid to th IMU. It succssfully liminatd th long-tm gyo ias. Sinc th shot-tm ias is much small, of th od of 50 dg/h, shot outags lik th ons simulatd h can idgd quit wll. Ths sults a confimd y thos in Hans (2004) and Gn (2004). m R (t) INS -fam m INS (t) m GPS a GPS INS GPS antnna a c INS c m m R c c-fam m m R c (t) = R (t) R c Oigin of m-fam Cama attitud Caliation INS attitud Figu 4: Pincipl of Aion Go-fncing Figu 2: Univsity of Calgay MEMS-asd IMU (without cas) Position Eo (m) Noth East Hight GPS gap GPS Tim (sc) Figu 3: Positional Dift duing GPS lockag 4. MATHEMATICAL MODELING Th fomulation of th dict go-fncing fomula is ath staight-fowad, fo dtails s fo instanc Schwaz (2000). Th standad implmntation of this fomula will, howv, caus difficultis whn low-accuacy gyos a usd. Th modifications ncssay in this cas will discussd in this chapt. Figu 4 dpicts aion moil mapping using a digital fam cama. Th mathmatical modl is givn in quation (1) and will usd as th standad modl in th following discussion. Th tms in th quation a listd in Tal 1. m i m m c c GPS nav ( t) + R ( t)[ s Rc + a a ] [1] i INS INS = Vaial Otaind fom m is th coodinat vcto of point (i) in th i mapping fam (m-fam) Unknown (3) m nav (t) is th intpolatd coodinat vcto of th navigation snsos (INS/GPS) in th m-fam S i is a scal facto, dtmind y sto tchniqus, las scanns o DTM m is th intpolatd otation matix twn th R ( t) navigation snso ody fam (-fam) and th m-fam (t) is th tim of xposu, i.. th tim of captuing th imags, dtmind y synchonization is th diffntial otation twn th C-fam R c and th -fam, dtmind y caliation c is th coodinat vcto of th point in th C- fam (i.. imag coodinat), c vcto twn IMU cnt and cama INS GPS INS pincipal point, dtmind y caliation vcto twn IMU cnt and GPS antnna cnt, dtmind y caliation Tal 1: Elmnts of th Gofncing Fomula Implmntation of this fomula quis intial and GPS masumnts fo th dtmination of th two tim-dpndnt tms on th ight-hand sid of quation (1), as wll as imag coodinat masumnts, in th c-fam, fo th dtmination c of th ojct point coodinat vcto. Th c-fam has its oigin in th pspctiv cnt of th cama, its z-axis is dfind y th vcto twn th pspctiv cnt and th pincipal point of th photogaph, and its (x,y)-axs a dfind in th plan of th photogaph and a masud with spct to th pincipal point. Th cosponding imag vcto is thfo of th fom: c x x p = y y, wh p f (x p, y p ) a th pincipal point coodinats f is th cama focal lngth

5 If instad of a fam cama, ith a pushoom scann o a Lida systm a modld, th only chang ncssay is in th c tm. It will hav th fom fo : 0 A pushoom scann = y y p f d sinα A LIDAR scann = 0 wh, d cosα d α Raw las ang (distanc) in las fam Scann angl fom nadi along y-axis of las fam, s Figu 5 Figu 5: LIDAR Scann Angl and Distanc Masumnt In addition, th misalignmnt matix c INS and R c and th offst vctos GPS INS hav to dtmind y caliation. A dtaild discussion of implmntation aspcts can found in El-Shimy (1996) fo land-vhicl applications and in Mostafa and Schwaz (2000) fo aion applications. Using Nwton s scond law of motion in a otating coodinat fam, th intial snso masumnts - spcific foc f and angula vlocity ω i, masud in th -fam can tansfomd into an Eath-fixd fam, say th Convntional Tstial Coodinat Fam(). Th sulting systm of diffntial quations is of th fom & v v& = R f 2Ωi v + g R& R ( Ωi Ωi ), (2) wh Ω i is th skw-symmtical fom of th angula vlocity vcto ω i and th dot aov a vcto (old low cas) o a matix (old capital) indicats diffntiation. Not that th m-fam in th go-fncing fomula (1) has n placd y th -fam. This systm is intgatd to yild th paamts on th lft-hand sid, namly position, vlocity, and th othogonal otation matix R twn th -fam and th -fam. Th dtmination of this tim-vaial matix is on of th cntal tasks of go-fncing. Th intgation of th systm of diffntial quation is statd y initializing th paamts on th lft-hand sid of th quation. Taditionally, this is don in stationay mod. In that cas, th initial vlocity is zo, th initial position is otaind fom GPS, and th initial ointation matix is dtmind y an alignmnt pocdu that maks us of acclomt lvling and gyo compassing. Th alignmnt is usually don in two stps. In th coas alignmnt simplifid fomulas a usd to otain pitch and oll fom acclomt masumnts and azimuth fom gyo masumnts, within an accuacy of a fw dgs. In th fin alignmnt small-angl o fomulas a usd in a filting schm to otain mo accuat stimats of th paamts. Th otation matix R can thn otaind fom th stimatd pitch, oll, and azimuth o an quivalnt paamtization, as fo instanc quatnions. This is th standad alignmnt pocdu if snso masumnts fom a navigation-gad intial systm a availal. Fo mdium and low accuacy systms, this mthod cannot applid. Bcaus of th unfavoal signal-to-nois atio fo ω i th gyo compassing pocdu will not convg. Thus, stationay alignmnt cannot usd with MEMS-asd o oth lowaccuacy IMUs. Th altnativ is in-motion alignmnt. This mthod has mainly n usd in aion applications, spcifically fo th in-ai alignmnt of intial systms. It is oviously dpndnt on using additional snsos, which in this cas a GPS civ outputs, i.. position and/o vlocity in th -fam. In-motion alignmnt maks us of th fact that vy accuat position infomation is availal at a high data at. It is thfo possil to dtmin accuat local-lvl vlocitis. By comining ths vlocitis with th ons otaind fom th stapdown IMU, th otation matix R can dtmind. Whn implmnting this appoach fo mdium o low accuacy IMUs two difficultis hav to addssd. Th fist on is that ith no azimuth infomation at all is availal, o that it is divd fom GPS vlocitis and is ath inaccuat. Thus, th standad small-angl o modls cannot usd any mo caus th azimuth o can lag. By fomulating th vlocity o quations, on can aiv at a st of quations that convgs quickly fo azimuth, vn if th initial os a lag. Schzing (1994) has givn a thoough discussion of th polm and its solutions, asd on ali wok y Bnson (1975). A land vhicl application, using a MEMS-IMU intgatd with GPS, is givn in Shin and El-Shimy (2004). Convgnc is fast in this cas, taking only aout 50 s. This ods wll fo aion applications wh, du to th high vlocitis, a tt signal-to-nois atio should futh impov th sults. Th scond difficulty is mo fundamntal. It has to do with th way in which th non-linaity in quation systm (2) and in th cosponding GPS masumnts a handld. Th standad appoach is to xpand th os in position, vlocity, and ointation into a Taylo sis and to tuncat th sis aft th lina tm. Th o quations otaind in this way a thn cast into stat vcto fom. By adding th linaizd GPS masumnts to th modl and y psnting th stat vaial distiution y a Gaussian andom vaial, th

6 xtndd Kalman filt (EKF) can fomulatd. It is a standad tool in ngining that is fquntly usd whn ith th systm modl o th osvation modl a non-lina. In an intsting pap Juli and Uhlmann (1996) hav dmonstatd that vn in a smingly innocuous situation - a oad vhicl moving along a cicl - th EKF dos not handl th nonlinaity in an accptal mann. Aft a quat cicl, th covaianc popagation sults in o llipss that do not psnt th actual situation. Th authos show quit convincingly that this is du to th linaizd covaianc popagation. To ctify th situation, th authos popos to chang this pat of th EKF. Thy appoximat th Gaussian distiution at a cafully chosn st of points and popagat this infomation though th non-lina quations. In this way th tansfomd Gaussian distiution will flct th nonlinaitis of th systm tt. Th nw filt, calld th Unscntd Kalman Filt (UKF) y its authos, has civd som attntion duing th past fw yas, s fo instanc Juli and Uhlmann (2002) and Cassidis and Makly (2003). A pap that comins in-motion alignmnt, lag azimuth modling and UKF fo MEMS /DGPS intgation is Shin and El-Shimy (2004). Although th UKF dos not oftn show a sustantial incas in accuacy, it sms to mo oust than th EKF in citical situations. Anoth appoach asd on Nual Ntwoks (NN) has n poposd y Chiang and El-Shimy (2002). Thy suggstd an INS/GPS intgation algoithm utilizing multi-lay nual ntwoks fo fusing data fom DGPS and ith navigation gad IMUs o tactical gad IMUs. Atificial Nual Ntwoks (ANNs) hav n quit pomising in offing altnativ solutions to many ngining polms, wh taditional modls hav faild o w too complicatd to uild. Du to th nonlina natu of ANNs, thy a al to xpss much mo complx phnomna than som lina modling tchniqus. Thy xtact th ssntial chaactistics fom th numical data as opposd to mmoizing all of it. ANNs, thfo, off a convnint way to fom an implicit modl without ncssaily stalishing a taditional, physical mathmatical modl of th undlying phnomnon (s Figu 6). In contast to taditional Kalman Filting modls, ANNs qui only a littl o no a pioi knowldg of th undlying mathmatical pocss. Fo GPS/INS intgation, this simply mans that intgation achitctu is platfom and systm indpndnt, as long as th implicit functional lationship twn th input and output is fixd. 5. FILTERING AND SMOOTHING Th discussion in th last chapt indicatd alady that modling and stimation a closly connctd in th gofncing polm. In tms of intsting cnt contiutions in filting and smoothing, th topics will discussd: Dnoising, AR modling, and simplifid smoothing. All th a post-mission mthods and a wll suitd to moil mapping. Dnoising is an impotant aspct in post-mission IMU modling caus th nois lvl of intial snsos is vy high, typically tims high than th minimum signal to solvd. In al-tim applications th standad way of tating this polm is to tust intgation to wok as a filt and to cafully slct th whit nois componnts in th Kalman filt. In moil mapping wh most applications a pocssd in post mission, dnoising oftn allows a mo find analysis caus th spctal and of intst can dfind and th high-nois and can liminatd. This is of impotanc whn on tis to modl th ias tms in th Kalman filt, as in cas of autogssiv modling (AR). Without dnoising th sults of an AR analysis com maninglss. Post-mission pocssing has also th advantag that tajctoy constaints can applid in oth fowad and ackwad diction, whil in al-tim Kalman filting this is only possil in fowad diction. Sinc an optimal smooth is tim consuming and quis considal stoag capacity, a simplifid modl fo ackwad smoothing will also ifly discussd. Band limiting and dnoising dscis a vaity of tchniqus that can usd to liminat whit o colod nois fom osvations. Skaloud t al (1999) w th fist to apply wavlt dnoising to th aw data fom intial snsos. Thy w al to show that th accuacy of th stimatd ointation paamts impovd y a facto of fiv, sulting in standad dviations of aout 10 acsconds fo pitch and oll, and of 20 acsconds fo azimuth fo a mdium accuacy IMU. In Figu 7, th ath damatic nois duction is shown whn applying a wavlt filt to a st of acclomt masumnts. Th nois dops fom a standad dviation of aout mgal (a) to aout 10 mgal (). Futh wok in this aa was don y Nouldin t al (2002) who usd fowad lina pdiction to dsign a tap dlay lin filt to impov th pfomanc of a FOG gyo y liminating th shot-tm angl andom walk. x Unknown modl f (.) Osvd Output d Nual ntwoks y + ˆ - f ( x, w) - Figu 6: Supvisd laning as modl idntification o function appoximation Figu 7: Y-Acclomt Spcific Foc Masumnts (a) Bfo Wavlt D-noising () Aft Applying th Wavlt 6 th LOD

7 Th stat vcto modl typically usd to pocss IMU data is mad up of two sts of paamts. Th fist st contains th os sulting fom th Nwtonian modl, i.. os in position, vlocity, and ointation. Th scond st contains th snso os, such as acclomt and gyo iass. Whil th modls fo th fist st of vaials a givn y th physics of th polm, th modls fo th scond st a ath aitay. Thy a usually chosn y looking fo a stuctu that maks stat spac modling simpl. Typical modls of this typ a andom amp, andom walk, o fist-od Gauss-Makov pocsss. Oftn a comination of ths modls is usd to fit a spcific o distiution, ut in gnal modl idntification tchniqus a not applid to vify th modl itslf. Sinc most of th tms to dtmind a long-wavlngth fatus, an AR modl can usd to dtmin what typ of modl stuctu would st fit th data. This ida was cntly studid y Nassa t al (2003). Rsults a quit ncouaging, spcially if d-noising is applid fist. Th data sts studid so fa all show significant scond- od ffcts, and in som cass small thid-od ffcts. Whn thy a includd in th stat-spac modl, sults impov y aout 30%. Howv, if th od of th modl is futh incasd, sults gt wos. Thus, it may fficint and advisal to dtmin th optimal modl od fo typical classs of IMUs in advanc and incopoat thm into th stat vcto. Post-mission pocssing, whn compad to al-tim filting, has th advantag that data of th whol mission can usd to stimat th tajctoy. This is not possil whn using filting caus only pat of th data is availal at ach tajctoy point, xcpt th last. Whn filting has n usd in a fist stp, on of th optimal smoothing mthods, such as th Rauch t al (1965) algoithm can applid. It uss th filtd sults and thi covaiancs as a fist appoximation. This appoximation is impovd y using th additional data that w not usd in th filting pocss. Dpnding on th typ of data usd, th impovmnt otaind y optimal smoothing can considal. This impovmnt coms at a pic, howv. Th pic is in tms of stoag quimnt and computation tim. It is not only ncssay to sto all stimatd stat vctos, ut also thi complt covaianc matics fo and aft updats. In cass wh th IMU is mainly usd to idg GPS-outags, such as in land-vhicl applications in uan cnts, a simpl algoithm can usd vy ffctivly. It calculats th diffnc twn th IMU position and th GPS position at th ginning and th nd of th outag. Th sulting diffnc is attiutd to a t 2 -o. Th choic of this simpl o mod sultd fom an analysis of th complt INS o modl fo shot-tim piods up to a fw minuts; s Nassa and Schwaz (2002) fo dtails. This modl has n tstd in oth aion and land-vhicl applications and has consistntly modld twn 90%-95% of th accumulatd o (iid). Rquimnts in tms of stoag and tim a minimal and th algoithm is vy simpl. Th o gaph fo a 85 scond outag and its modl fit is shown in Figu 8. Paamtic Modl Actual Eos Figu 8: SINS (a navigation-gad - Honywll LRF-III) Positioning Eos duing DGPS Outag 6. CURRENTLY ACHIEVABLE ACCURACIES AND ONGOING DEVELOPMENTS Th tals of sults shown in th following a not asd on a comphnsiv analysis of pulishd sults. Thy a ath sampls of sults achivd with spcific imaging systms and hav n takn fom company ochus and tchnical pulications. Th authos think that thy a psntativ fo th systms that hav n discussd pviously. Th following will includ th xampls of post-mission systms, on aion, on van asd, and on potal, and on aion al-tim systm. Th accuacy spcifications fo th Applanix family of POS/AV TM aion dict gofncing systms a listd in Tal 2 (Mostafa t al, 2000). Th pimay diffnc in systm pfomanc twn th POS/AV TM 310 and POS/AV TM 510 systms is th ointation accuacy, which is dictly a function of th IMU gyo difts and nois chaactistics. Fo xampl, th gyo difts fo th POS/AV TM 310 and POS/AV TM 510 systms a 0.5dg/h and 0.1dg/h, spctivly. Whil th cosponding gyo noiss a 0.15 and 0.02 dg/sqt(h), spctivly. Tal 2: Post-pocssd POS/AV TM navigation paamt accuacy (Mostafa t al, 2000] Th scond xampl is fo land MMS. Accuacis achivd with many land MMS systms, such as th VISAT systm (El- Shimy, 1996) a suital fo all ut th most dmanding cadastal and ngining applications. Accuacis in this cas mainly dpnd on availaility of GPS and how long th INS systms can wok indpndntly in stand-alon mod. If GPS is availal, th positioning accuacy is unifom at a lvl of 3-5 cm (ms). If GPS is not availal, th positional accuacy dpnds on th lngth of th outag, s Tal 3. It lists th stand-alon accuacy of a stapdown navigation-gad systm λ h φ

8 (imar inav-rqh) fom sconds. Ths sults hav n otaind using th Univsity of Calgay KINGSPADT M GPS/INS intgation softwa ( Futh impovmnts in position and azimuth accuacy can achivd if an odomt is addd fo lngth contol and a two-antnna GPS fo azimuth contol. An intsting xampl on th us of a oad vhicl in an xtm situation, th uan canyon nvionmnt of cntal Tokyo is givn in Schzing (2002). Although adquat GPS covag was dnid fo aout 50% of th tim, a position accuacy of tt than25 cm was maintaind fo aout 90% of th suvy. GPS Outags Piods KF (m) Vhicl motion 30 sc 0.08 Staight lin 60 sc 0.09 Cicl 30 Sc 0.13 Cuv 60 Sc 0.06 Static 120 Sc 0.12 Static 180 Sc 0.3 Staight lin Tal 3: Accuacy of th imar inav-rqh INS systm in stand-alon mod. Th thid xampl givn h is a ackpack MMS dvlopd at th Univsity of Calgay. Th ackpack MMS compts in oth accuacy and initial cost with cunt mthods of GIS data collction, whil offing incass in data collction fficincy and flxiility that only an MMS can povid. Th ackpack MMS uss a Lica Digital Magntic Compass (DMC) fo attitud dtmination, a singl Kodak DC260, and a Novatl OEM4 civ. Th systm s opational stps a ssntially th sam as any MMS in th sns that th DMC and th GPS povids th dict gofncing infomation fo th camas. Th only diffnc is that caus of th low accuacy of th DMC divd attitud, th systm is augmntd with a Bundl Adjustmnt softwa, s Ellum (2001). In this cas, th dict gofncing paamts a usd as apioi infomation on th xtio ointation paamts. Th asolut accuacis of th Backpack MMS in a vaity of configuations a shown Tal 4. Fom th tals, it can sn that with as fw as fiv imag point masumnts at a 20m cama-to-ojct distanc it is possil to achiv accuacis that satisfy many mapping applications, fo mo dtails s iid. Th systms psntd so fa a woking in post-mission mod of opation. In this mod of opation, th data is collctd in th vhicl (van, aiplan, o ship) and pocssd off-sit in od to xtact th infomation of intst. Du to th postmission mod of opation, vy high accuacy, in position ( 0.1 m "RMSE") and attitud ( 0.02 dgs "RMSE") can achivd. This is accomplishd y using th pcis GPS cai phas in Diffntial mod (DGPS uss two GPS civs; on in static mod ov known contol point and th scond on th vhicl. By tightly coupling DGPS and INS data though Kalman filting th aov accuacis can achivd. Num of Imag Point 3 Imags Hoizontal Ma x (m) RM S (m) Vtical Ma x (m) RM S (m) 5 Imag Points Imag Points 6 Imags Imag Points Imag Points Tal 4: Backpack MMS Systm Asolut Accuacy (20m cama-to-ojct distanc) Although in most mot snsing applications, th is no nd fo al-tim pocssing of th data, th a som mging applications, spcifically fost fi fighting; in which th quimnt fo al-tim mapping is mo impotant than th achivmnt of highst possil accuacy. On of th main polms in comating fost fis is monitoing th tim histoy of th fi. Undstanding th siz, location, and spd of advanc of th fi font is citical to th optimal allocation of fi-fighting soucs and th maintnanc of th fi cw safty. Invstigations of majo wild-land fi accidnts involving loss of lif, oftn indicat that th cws cam impild caus of insufficint o untimly infomation aout th location and spd of th fi advanc. Th F 3 systm, ing dvlopd at th U of C, intgats imaging snsos (Thmal InfaRd TIR Camas) with al tim navigation tchnologis (Wid Aa Diffntial GPS WADGPS and low cost INS). Th systm is vy usful in poting th xact situation of fis, assisting th Fost Fi Infomation Systms (FFIS) in accuatly assssing th fi and pcisly dicting wat-oms and fi-fighting cws. Th us of infad/thmal camas, which sns th hat mittd in th fom of infad adiation, will nal aly dtction and location of fost fis in ducd visiility du to haz, smok o daknss. Rcnt systm tsting ov contolld fi pits of known coodinats indicats that th systm s al-tim positional accuacy in idntifying hotspots is aout 6m RMS (Wight and El-Shimy, 2003), whn using singl civ psudo-angs.. Kinmatic GPS contolld aial photogammty and dict go-fncing using DGPS/INS hav com matu tchnologis in oth th scintific and commcial mapping communitis. Vitually all aion mapping systms now intgat a GPS civ and INS unit with thi cama. Unfotunatly, on th softwa sid, th intgation of GPS o GPS/INS and photogammty is not as clos. Typically, th GPS data is includd in th photogammtic undl adjustmnt as pocssd positions only (Schmitz t al, 2001; Mikhail t al., 2001) and similaly th GPS/INS data a usd fo dict gofncing. In ffct, th pocssing ngins of GPS (o GPS/INS) and photogammty opat lagly in isolation. This implmntation has ovious nfits in tms of simplicity. Howv, a mo fundamntal fusion of th GPS and INS data

9 into th undl adjustmnt may povid impovmnts in oth accuacy and liaility. A tight coupling of th GPS and photogammtic pocssing ngins wh th GPS cod psudoangs a dictly includd in th undl adjustmnt is cuntly invstigatd at th univsity of Calgay [Ellum, 2004]. Th goal of this intgation is to impov th accuacy and liaility whn compad to th simpl inclusion of GPS positions. It is hopd that accuacis simila to thos otaind y a wid-aa augmntation systm can achivd. A mo fa-aching stp would th dvlopmnt of two-way infomation shaing twn a photogammtic adjustmnt and th kinmatic GPS/INS pocssing. In this achitctu, a Kalman-filt-asd kinmatic GPS/INS pocsso povids pcis position and ointation to th photogammtic adjustmnt. In tun, th photogammtic adjustmnt povids position updats to th Kalman filt. Ths position updats should aid th amiguity solution of th GPS/INS pocsso, making th nti pocss mo accuat and mo oust. This will of majo impotanc to moil mapping with land vhicls, as it will sult in a mo consistnt mapping spac accuacy. This will duc th quimnt fo zo-vlocity updats (ZUPTS), whn signal outags occu (i.., idging), and will allow to initializ th GPS amiguitis to intg valus following outags. 7. CONCLUSIONS T Looking at th dvlopmnt of Moil Mapping Systms ov th past fiftn yas th following conclusions can dawn: Moil mapping, th comination of digital imaging and go-fncing, has dvlopd fom a topic of acadmic intst to a commcially vial industy with aion, land-asd, and main applications. With th still apid dvlopmnt of high-solution digital fam camas and th cunt tsting of digital scanns that pomis high solution than filmasd camas, conomy and fficincy a on th sid of this nw tchnology. Th go-fncing tchnology has matud, du to th ongoing finmnt and miniatuization of GPSciv hadwa and th us of low and mdium cost IMU s, and has com mo affodal duing th past dcad. It appas that a majo stp fowad is imminnt as MEMS snso tchnology will sult in considal cost ductions fo tactical-gad gyos and in nw multi-snso systm concpts. Th ongoing dvlopmnt of mathmatical modling and advancd post-mission stimation tchniqus will futh incas accuacy and oustnss of th solutions. Futhmo, som mging al-tim polms may hav considal socio-conomic impact in applications such as fi fighting o offsho pollution contol. 8. REFERENCES Bad, J. (1993): Low-Cost GPS/INS. Poc. ION GPS-93, Salt Lak City, USA, pp Bäumk, M. and A. Mattissk (1992): Intgation of a Fi Optical Gyo Attitud and Hading Rfnc Systm with Diffntial GPS. Poc. ION GPS-92, Aluququ, USA, Spt , 1992, pp Bnson J, D.O. (1975): A Compaison of Two Appoachs to Pu-intial and Doppl-intial Eo Analysis. IEEE Tansactions on Aospac and Elctonic Systms, Vol. AES- 11, No 4, July Cannon, M.E. and K.P. Schwaz (1990): A Discussion of GPS/INS Intgation fo Photogammtic Applications. Poc. IAG Symp. # 107: Kinmatic Systms in Godsy, Suvying and Rmot Snsing, Banff, Spt , 1990, pp (pulishd y Sping Vlag), Nw Yok Chiang, K.W. and El-Shimy, N. (2002): INS/GPS Intgation using Nual Ntwoks fo Land Vhicl Navigation Applications, Pocdings of th US Institut of Navigation (ION) GPS 2002 mting, Sptm 24-27, Ogon Convntion Cnt, Potland, Ogon, USA (CD). Cosandi, D., M.A. Chapman, T. Ivanco (1993): Low Cost Attitud Systms fo Aion Rmot Snsing and Photogammty. Poc. of GIS93 Confnc, Ottawa, Mach 1993, pp Cassidis, J.J. and F.L. Makly (2003): Unscntd Filting fo Spaccaft Attitud Estimation. J. of Guidanc, Contol, and Dynamics, July/Aug. 2003, Vol. 26, No. 4, pp Dostl,C., Zitl, W., Jacosn, K., 2002: Gomtic Caliation of th DMC: Mthod and Rsults, ISPRS Com I and PECORA, Dnv 2002 Ellum, C. (2004): Intgation of Raw GPS Masumnts into a Bundl Adjustmnt. In XX ISPRS Congss, Intnational Achivs of Photogammty and Rmot Snsing, Intnational Socity of Photogammty and Rmot Snsing (ISPRS), Istanul, accptd fo pulication. Ellum, C (2001), Th Dvlopmnt of a Backpack Moil Mapping Systm, (M.Sc. thsis), UCGE Rpot No , Dpatmnt of Gomatics Engining, th Univsity of Calgay. El-Shimy, N. and K.P. Schwaz (1993): Kinmatic Positioning in Th Dimnsions Using CCD Tchnology. Poc. IEEE/IEE Vhicl Navigation & Infomation Systm Confnc (IVHS), Octo 12-15, 1993, pp El-Shimy, N (1996), Th Dvlopmnt of VISAT - A Moil Suvy Systm fo GIS Applications, (Ph.D. thsis), UCGE Rpot No , Dpatmnt of Gomatics Engining, th Univsity of Calgay. Gn, J.A. (2004): Pogss in Intgatd Gyoscops. Poc. IEEE PLANS 2004, Monty, USA, Apil 26-29, 2004, pp Hans, J.G (2004): Honywll MEMS Intial Tchnology & Poduct Status. Poc. IEEE PLANS 2004, Monty, USA, Apil 26-29, 2004, pp Juli, S.J. and J.K. Uhlmann (1996): A Gnal Appoach fo Appoximating Nonlina Tansfomations of poaility Distiutions. Tchnical Rpot, Dpatmnt of Engining Scinc, Univsity of Oxfod, UK. Juli, S.J. and J.K. Uhlmann (2002): Th Scald Unscntd Tansfomation. Poc. IEEE Amican Contol Confnc, Anchoag, USA, 2002, pp.4555 ñ 4559.

10 Lapucha, D., K.P. Schwaz, M.E. Cannon, H. Matll (1990): Th Us of GPS/INS in a Kinmatic Suvy Systm, Poc. IEEE PLANS 1990, Las Vgas, Mach 20-23, 1990, pp Lipman J.S. (1992): Tad-Offs in th Implmntation of Intgatd GPS Intial Systms. Poc. ION GPS-92, Aluququ, USA, Spt , 1992, pp Mikhail, E. M., J. S. Bthl, and J. C. McGlon, 2001, Intoduction to Modn Photogammty. John Wily and Sons, Inc., Nw Yok. Mostafa, M.M.R. and K.P. Schwaz (2000): A Multi-Snso Systm fo Aion Imag Captu and Gofncing. PE&RS, Vol. 66, No. 12, pp Mohamd Mostafa, Jo Hutton, Eik Lithopoulos (2000a): Gound Accuacy fom Dictly Gofncd Imagy, GIM Intnational Vol. 14, No. 12, pp. Mostafa, M. (2004): Th Digital Snso Systm Data Flow, Th 4 th Intnational Symposium on Moil Mapping Tchnology, Kunming, China, Apil 2004 (CD). Nassa, S. and K.P. Schwaz (2002): Bidging DGPS Outags in Kinmatic Applications Using a Simpl Algoithm fo INS Bias Modling. Poc. ION GPS-2002, Potland, USA, Spt , 2002, pp Nassa, S., K.P. Schwaz, A. Nouldin, N. El-Shimy (2003): Modling Intial Snso Eos Using Autogssiv (AR) Modls. Poc. ION NTM-2003, Anahim, USA, Januay 22-24, 2003, pp Nouldin, A., D. Ivin Halliday, H. tal, M.P. Mintchv (2002): Nw Tchniqu fo Rducing th angl andom walk at th Output of Fi Optic Gyoscops Duing Alignmnt Pocsss of Intial Navigation Systms. Opt. Eng. Vol. 40, No. 10, pp (Octo 2001). Novak, K Data collction fo multi-mdia GIS using moil mapping systms. Gomatics Info Magazin (GIM). Vol. 7. No. 3. pp H.E. Rauch, F. Tung, C.T. Stil (1965): Maximum Liklihood Estimats of Lina Dynamic Systms, AIAA J., Vol. 3, No.8, pp Schzing, B.M. (1994): Intial Navigato Eo Modls fo Lag Hading Unctainty. Poc. Int. Symp. Kinmatic Systms in Godsy, Gomatics and Navigation, Banff, Canada, Aug. 30- Spt. 2, 1994, pp Schzing, B.M. (2002): Intially Aidd RTK Pfomanc Evaluation. Poc. ION GPS-2002, Potland, USA, Spt , 2002, pp ñ Schmitz, M., G. W una, and A. Bagg, 2001, Bnfit of Rigoous Modling of GPS in Comind AT/GPS/IMU-Bundl Block Adjustmnt. In OEEPE Wokshop on Intgatd Snso Ointation, Oganisation Euopn d Etuds Photogammtiqus Expimntals/ Euopan Oganization fo Expimntal Photogammtic Rsach (OEEPE), Hannov. Schwaz, K.P., M.A. Chapman, M.E. Cannon, P. Gong (1993): An Intgatd INS/GPS Appoach to th Gofncing of Rmotly Snsd Data. PE&RS, Vol. 59, No. 11, pp Schwaz, K.P. (2000): Mapping th Eath s Sufac and Its Gavity Fild y Intgatd Kinmatic Systms. Lctu Nots of th Nodic Autumn School, Fvic, Noway, Aug. 28 Spt. 1, 2000, pp. Shin, E.H. and N. El-Shimy (2003): INS Toolox, a MatLa softwa fo GPS/INS intgation, Dpatmnt of Gomatics Engining, th Univsity of Calgay ( s/softwa/instooloxfomatla.php) Shin, E.H. and N. El-Shimy (2004): An Unscntd Kalman Filt fo In-Motion Alignmnt of Low-Cost IMU s, IEEE PLANS 2004 APRIL 26-29, MONTEREY, CA, pp Skaloud, J., A.M. Buton, K.P. Schwaz (1999): Dtction and Filting of Shot-tm (1/f) Nois in Intial Snsos. Navigation, Jounal of Th Institut of Navigation, Vol. 46. No. 2. pp Wight, B. and El-Shimy, N. (2003): "Ral-Tim Dict Gofncing of Thmal Imags Fo Idntification and Location of Fost Fi Hotspots, 6th Confnc on Optical 3D Masumnt Tchniqus, Zuich, Switzland, Sptm 22-25, 2003 (CD).