How To Create A Virtual Telescope Service For A Mobile Device

Transcription

1 Virtual Telescpe Services fr Mbile Devices Sergey Balandin Alexandra Reyss Nkia Research Center Helsinki, Finland Petrzavdsk State University Petrzavdsk, Russia Abstract Fast develpment f the mbile technlgies allws creating new services, which help peple t address different demands in all spheres f their life. Gd examples f such fast grwing areas are ge-psitining and navigatin services. Humans were always inspired by the stars and a new class f astrnmy-riented services might be very well taken by the users. Nwadays there is a few Internet services that address this area, but having this service n the mbile device will prvide user with cmpletely new experience. One f the mst interesting fr research grup f services is grup which address t services which cmbine reality and virtual reality. The paper discusses ne f thse services fr mbile devices. The main idea f ur service is t allw users t get infrmatin f different sky bjects (planets, cnstellatins and thers) withut special astrnmical equipment but just by means f mbile device. In particular we prpse the new astrnmical service that turns mbile device int handheld guide f the stars sky and even t the persnal telescpe. The prpsed service can be used in different areas f human life, e.g. frm prfessinal training f pilts and educatinal curses fr schl students that can be rganized in the mst cmfrtable and cl frm, t just fulfilling user s curisity abut stars and space r even fr fun. The paper describes architecture fr the virtual telescpe grup f services and defines functinality f each key mdule. We include descriptin f mathematical part f service and describe main principal frmulas fr data transfrming. As a result we prpse full-functinal service and this paper discuss the prttype f virtual telescpe made n the WRT technlgy. The paper is cncluded by the discussin n the ptential and perspectives f the prpsed services and presentatin f the implementatin plans. The prject is dne within scpe f FRUCT prgram and it basic principles were presented at the Symbian essay cmpletin Als we will present the prgress reprt f this prject n 6 th FRUCT seminar. Index Terms: virtual telescpe, mbile service, stars guide, teaching astrnmy. I. INTRODUCTION Fr centuries humans bserve the stars, which created ne f the lngest utstanding demands - t learn mre abut ur universe. Sme Internet services are trying t address this demand, hwever studying the stars sky frm indrs is nt as useful and cl as if this service wuld be available when user is utdrs and watching the stars. This paper gives an verview f a prject running within frame f FRUCT prgram [1], which defines the new grup f services and related Symbian applicatin fr mbile device. The ultimate gal f this prject is t prvide functinality f the virtual telescpe cmbined with the stars guide, linked t the crrespnding bks f ancient legends and ther resurces t maximize user experience frm watch the sky, and later this service can be even extended with the virtual phtgraphy f the starts, which will maximize use f the available hardware and Internet access. Nwadays ne can find a number f different astrnmic services in Internet. A well knwn example is Ggle Sky service [2]. But these services dn t have versins fr mbile devices. Anther gd example is the Starmap applicatin [3] that is a stargazing cmpanin fr iphne r ipd Tuch. It allws users t find cnstellatins, planets and shting star znes. The authrs claim that it is a cmplete hand-based planetarium fr beginners and 19

2 advanced astrnmers, it includes infrmatin abut 120,000 visible stars, 200 main stars with names, kind and spectrum and 150 galaxies and nebulae. Hwever this applicatin is just an encyclpedia f stars and desn t prvide user with the telescpe experience, as well as ther f the abve listed services, i.e. database f ancient legends fr the cnstellatins, etc. Analysis f the available prir art has shwn that currently there is n slutin t use mbile device fr zming and taking phts f the certain areas f stars sky. The prject target is even mre ambitius - hw the mbile phne can emulate behavir f the telescpe and deliver crrespnding experience t the user. The prpsed virtual telescpe service is targeted in prviding a number f additinal services and imprvements f the bservatin quality cmparing t the classical astrnmical telescpe. Anyne wh gazed thrugh the eyepiece f an astrnmical telescpe knws that except fr the Mn and planets, extra-slar astrnmical bjects are hard t bserve. This is mainly due t lw surface brightness, but als depends n the seeing, sky brightness and telescpe aperture. The augmented astrnmical telescpe [4] prpses a system which prjects images f astrnmical bjects (nebulae and galaxies), animatins r additinal infrmatin directly int the eyepiece f an astrnmical telescpe. As the telescpe rientatin is tracked cntinuusly, the prjected image is adapted in real-time t the bject that is currently visible thrugh the eyepiece. The service is deplyed in public bservatries and let visitrs t experience the richness f deep sky bjects while directly gazing at them thrugh a telescpe. This is an interesting example f hw prfessinal telescpe data can be delivered t the mass users. But the prpsed apprach is nt scalable enugh t be used fr mbile device based slutin as we cannt allcate persnal telescpe fr every user. Als the service cntrl mechanism and UI are nt applicable fr the mbile device. Als we want t mentin paper Lk beneath the surface with augmented reality [5], which talks abut mapping virtual bjects t the real-time captured vide. The paper is rganized as fllws. The secnd chapter discusses idea and prvides descriptin f the prpsed service. In the third chapter we discuss the implementatin details f the service and especially fcus n the verall service architecture, service cntrl, rganizatin f cntent delivery and the user experience. The next chapter initiates discussin arund the tpic f new services that pen new hrizns f the user experience by presenting t the user a cmbinatin f the real and virtual wrlds infrmatin. And the paper is cncluded by the summary f main results, presentatin f the future plans, acknwledgments and the list f references. II. DESCRIPTION OF THE SERVICE The first service starpedia prvides user with a scheme f stars in the sky that are bservable in the given time and lcatin. By default the service takes lcal time and lcatin f the mbile device. An imprtant feature f starpedia is rientatin f the stars scheme inline with the current rientatin f the mbile device, s that it wuld be really easy fr the user t map visible stars t the cnstellatins and stars at the scheme. By pinting by jystick t the internal area f cnstellatin n the screen, the user gets infrmatin abut its main stars and ther related references, e.g. Ancient Greek myth, etc. This infrmatin can be stred lcally (e.g. fr the best visible cnstellatins) r btained frm the backend service r even by direct request t crrespnding Internet resurce. By pinting t particular star n the scheme user gets all main facts abut it, including name, brightness, distance, and s n. The next service is stars-identifier. The user experience is that the user gets the starpedia page that crrespnds t the area f the sky t which the device camera is pinting in the given mment f time. The mtin and cmpass sensrs shuld allw quite accurately define 20

3 directin and angle f the camera pinting t the sky. The interesting research questin is hw t use camera tgether with rientatin sensrs f the mbile device fr increasing accuracy f defining area f the stars sky bserved by the user? One idea n hw t address this questin was fund in the patent applicatin Optical see-thrugh augmented reality mdified-scale display [6]. Withut ging t implementatin details, which are utside f scpe f this paper, the main cnclusin is that implementatin f such synchrnizatin scheme wuld require a lt f effrts, but it shuld be pssible fr nwadays Symbian mbile devices. The next service is virtual telescpe. In starpedia r stars-identifier mdes the user can press zm and fr the selected area f stars sky the service will find and dwnlad the crrespnding phts frm the selected cntent prviders, e.g. NASA, RsKsms, etc. As a result, the user gets access t the best astrnmic cntent (phts f galaxies, planets and mns in high reslutin, etc.) that will be nt just nice lking pictures but the real pictures f bjects that user want t see better. Fr example, using this service the user can study craters and surface f the Mn, see ther planets and their mns and s n. Later als cmmercial services can be intrduced, e.g. request fr actual picture. Mst peple realize that almst there are n visible changes f the stars sky during ur life perid, s the archive pictures and current pictures are almst the same, especially taking in accunt reslutin f the mbile device screen. But driven by rmantics and persnalizatin reasns, many users still want t get actual pictures f the sky and ready t even pay fr it if price f this service will reasnable lw (within range f 1USD per picture). Fr example, sme peple have mentined that it is very rmantic and gd memry if they wuld be able t take high quality actual pictures f their hrscpe cnstellatins n the first r last day f the hlidays. Fr this service we need t build a netwrk f astrnmical telescpes with phtgraphy capability. The netwrk can cnsist f varius telescpes, frm semiprfessinal telescpes in persnal use and small cmmercial planetariums, and up t prfessinal bservatries. In the beginning the netwrk will primary cnsists f semiprfessinal telescpes wrking fr a share f the service incme. Fr this telescpes we need t develp mechanics fr autmatic cntrl f the telescpe psitining and phtgraphy, s that the telescpe wner wuld switch telescpe int autmatic service mde at any time when desn t need it. The mechanics can be built based n principle f the telescpe cntrl mechanics prpsed in [4]. The mbile device makes request fr a picture f a given sectr f the sky and alng with the user crdinates send it t the clses telescpe f the service netwrk. The telescpe sftware calculates sky zne f interest depending n the telescpe and user lcatins and gives the crrespnding psitining cmmand t the telescpe mechanics, makes pht and send it t the user. In case f multiple requests, the psitining system builds an ptimal psitining chain t minimize physical mvement f the telescpe, but als guaranty that all requests will be served within X minutes. III. IMPLEMENTATION The services can be implemented as standalne applicatins r as extensins f the existing psitining services, e.g. Nkia Maps. The first dem f the service is targeted fr nwadays available devices. The implementatin wrk is just started and it is bvius that implementatin f the abve listed services will require extensive use f the device sensrs, search engine fr finding relevant cntent in Internet, and even develpment f the image recgnitin algrithm fr the device camera t recgnize as many star-dts as pssible. In fact all needed infrmatin is available, but putting it tgether is a big, challenging and very interesting research and develpment wrk. 21

4 A. THE SERVICE ARCHITECTURE The services functinality is distributed between the mbile device client and backend server, and it relies n use f the public free astrnmical databases available in the Internet. The high-level definitin f the Virtual Telescpe service architecture is illustrated by Figure 1 and belw the figure we prvide a list f the main service cmpnents and their functinality. Figure 1: The Virtual Telescpe service architecture fr mbile devices. 1. User Interface (UI) prvides czy interface fr user s interactin with the service and the virtual telescpe experience, and implements functins fr user cntrl f the service and results representatin. 2. Sky-psitin mdule defines area f the sky t which the user is pinting. It cnsists f the accelermeter and cmpass directin recgnizers and ptinal camera mdule. The embedded accelermeter sensr has 3 axes fr dwn, frward and side mves. By cmbining data frm these axes we get vectr f the device acceleratin in the 3D space, but withut directin, as there is n difference in gravitatin if the phne is riented t the nrth r suth. T reslve this prblem we can use cmpass that is als available fr a number f devices, e.g. the navigatr phne (Nkia 6710, 6210, etc.). Camera is ptinal mdule that refines the telescpe directin by recgnizing maximum f the camera visible starts (desn t wrk with current lens quality) and cmparing it t the stars sky pattern. 3. GEO-psitining mdule defines user s gegraphical crdinates by using GPS sensr r frm the serving base statin, as even maximum radius f 50 km gives gd enugh accuracy fr the service. The user lcatin is btained in fllwing frmat: n nn nnn N r S and w ww www W r E. 4. Calculatin f requested Sky-crdinates mdule gets data frm the accelermeter (x, y and z crdinates) and GEO-psitining mdule and builds the target sky crdinates in frm f Ra and Dec. 5. Frming Sky-picture request query mdule The main functins f this mdule: 22

5 Frms a request t the backend server Receives the result images and prepare them fr utput t the user 6. Back-end server In the beginning the backend server will be relatively simple mdule that makes requests fr the images and perfrms adjustment f the resulting images t the mbile device. We have identified and are planning t use a number f Internet resurces where astrnmical data is available fr free dwnlad. B. SERVICE CONTROL AND USER EXPERIENCE When the target zne is defined, the service makes crrespnding request t the backend server that makes further search f the apprpriate infrmatin n web and returns stars sht as shwn in Figure 2. Figure 2: UI with starts sky view in the Virtual Telescpe service. In the beginning the backend server will be relatively simple mdule that makes requests fr the images and perfrms adjustment f the resulting images t the mbile device. We have identified and are planning t use a number f Internet resurces where astrnmical data is available fr free dwnlad. IV. MATHEMATICAL DEFINITION OF THE SERVICE PROCESSING UNIT This chapter describes hw t transfrm data cllected by the varius sensrs f the mbile device t get crdinates f a sky bject t which user is pinting in the given time and lcatin. This cnsists f the fllwing main steps: - definitin f the utput parameters frm each service mdule; - data transfrmatin t the crdinates in frmat Ra and Dec; - taking int cnsideratin angle f mbile device inclinatin. A. DEFINITION OF OUTPUT PARAMETERS FROM EACH SERVICE MODULE Frm Sky-psitining mdule: β angle between directin t which the user is pinting and the nrth ple. γ angle between directin t which the user is pinting and the hrizntal. Frm Ge-psitining mdule we get user gegraphical crdinates. As a result, the user lcatin is btained in fllwing frmat: n nn nnn N r S 23

6 w ww www W r E Tgether this data allws defining in what pint n Earth the user is lcated at the given mment f time and t what part f sky he/she is pinting. B. DATA TRANSFORMATION TO THE COORDINATES IN FORMAT RA AND DEC First it is necessary t cnvert crdinates f user lcatin t declinatin δ(dec). Fr simplificatin f the task let s assume that the Earth is ideal sphere. Calculatin f δ crdinate is nt a big prblem and can be dne using principle illustrated by Figure 2. Figure 2. Definitin f declinatin. This picture shws a lateral cut f the Earth. Fr the user at the latitude δ in the nrth hemisphere, the declinatin is equal t his/her nrth latitude, and if user is lcated in the suth hemisphere the declinatin is equal t the suth latitude taken with the negative sign. δ = n nn nnn N r δ = -n nn nnn S The abve illustrates calculatin f the direct ascensin α (Ra). Because the Earth is rtating in plane f x-y crdinates, the direct ascensin is als depends n time. If we knw angle between lngitude and the x-axis (x-axis is directed twards the pint f spring equinx) it is pssible t define crdinates f direct ascensin depending f the time. Let s nw make the fllwing definitins: α(t) angle between x-axis and lngitude f user s lcatin (it is direct ascensin α r Ra); t time f measurement (current time), where in fact α(t) is a functin f time; αg(t) GST (Greenwich Mean Sidereal Time r GMST); λ the current lngitude f the user. Figure 4 illustrates Earth cut by the plane parallel t equatr and ging thrugh the pint in which user is lcated. 24

7 Figure 3. Definitin f direct ascensin. α(t) = αg(t) + λ, where w ww' www'' W 360 w ww' www'' E The lcal sidereal time is calculated based n the sum f GMST and the user lngitude. Definitin f functin αg(t) can be fund in different bks, e.g. in US Naval Observatry's Astrnmical Almanac [7]. αg(δt) = αg(0 h ) + ω* Δt, where αg(0 h ) time fr 0 h f certain data, ω speed f rtating the Earth, ω = radian/s Δt UTC-time α g (0 h ) = s s T u + 0 s T 2 u T u T u = d u /36525, d u number f days since JD (1 January 2000, 12h UT1) Thus we get Ra and Dec crdinates f the current user lcatin. C. TAKING INTO CONSIDERATION ANGLE OF MOBILE DEVICE INCLINATION Let s cnsider that δ new declinatin and new direct ascensin. These are the crdinates f a sky zne t which the camera f user s mbile device is pinting. By means f sme transfrmatin f crdinates we get new declinatin and new direct ascensin. Depends n what directin user shws it is necessary t make transfrmatin f angle β. 25

8 , , , , Based n that, Figure 4 illustrates hw the result transfrmatin can be made. Figure 4. Transfrmatin f crdinates As a result we get the fllwing frmulas fr calculating new declinatin and new direct ascensin: , , , 0 ', , , ' , , ' , , 0 180, ', , 360 0,

9 The service develpment wrk is still in wrapping up phase and a lt f research and implementatin wrk is still t be dne. Fr example, current definitin f the service requires all-time cnnectin t the netwrk, as nly very limited data cashing can be made fr the mbile device. T reduce the crrespnding expenses and allw efficient cashing we need t prpse a methdlgy fr predicting user behavir. Anther research questin is hw t get sharper images and better stars pattern recgnitin based n data received frm the mbile device camera. This prject will becme a multiyear student activity. The service shuld be available fr Symbian devices, which are equipped with acceleratin and mtin sensrs, have reasnably gd camera and enugh lcal memry t stre basic database. As a reference smartphne we are ging t use Nkia 6210 Navigatr. The first prttype implementatin f the service is under develpment and it will be dne using WRT technlgy [8]. In the future when devices will have better ptics and allw better recgnitin f the star-dts and their brightness, the ptinal camera sky-psitining mdule will be implemented t allw faster and mre accurate definitin f the target area f the sky. If the prject wrk will prgress accrding t the current plan and n new majr bstacles will be fund, the first prttype dem f the service fr Symbian devices is expected by the end f this year. ACKNOWLEDGMENT The article is prepared within the scpe f Finnish-Russian University Cperatin in Telecmmunicatins (FRUCT) prgram [1]. The authrs wuld als like t thanks Nkia university cllabratin prgram fr prviding publicatin grant and all FRUCT experts fr their review cmments. REFERENCES [1] Official web page f Finnish-Russian University Cperatin in Telecmmunicatins (FRUCT) Prgram. The Virtual Telescpe prject page. [2] Ggle Inc., Official web page f Ggle Sky, [3] F. Descamps, Dwnlad page f Starmap applicatin fr iphne OS 2.0, CNet Australia, [4] A. Lintu, M. Magnr, Augmented Astrnmical Telescpe, MPI Infrmatik, Prceedings f Secnd GI-Wrkshp VR/AR, [5] G. Rberts, A. Evans, R. Hllands, B. Denby, S. Cper, A. Ddsn, Lk Beneath the Surface with Augmented Reality, [6] R.T. Azuma and R. Sarfaty, US patent : Optical see-thrugh augmented reality mdified-scale display, Patent review cmmunity, [7] The Astrnmical Almanac n-line, [8] Frum Nkia, Web Run Time widgets technlgy fficial web page,