4. Principles of Picture taking 4 hours

Transcription

1 Leture /3/003 Conet Hell/Pfeiffer February Priniles of Piture taking 4 hours Aim: riniles of iture taking (normal ase, onvergent for oint measurements, flight lanning) flight lanning (arameter, hoto sale, ameras, instruments for outer orientation) 4.. Planning of terrestrial hotogrammetry Deending on the osition of the amera we ould divide hotogrammetry to ground, aerial and sae. The ground hotogrammetry is divided to terrestrial and lose range hotogrammetry. The ase of the lose range hotogrammetry is when the distane to the registered objet is less then 300m (in some soures no more then 00m). Close range hotogrammetry inludes three main areas of aliation: arhitetural (and arheologial), ivil engineering hotogrammetry, industrial hotogrammetry, medial hotogrammetry (biomedial or bioengineering). Some seial arts of arhitetural hotogrammetry ould be searated as ivil engineering hotogrammetry, when objet of measurement are seial engineering objets and onstrutions, that are not buildings like bridges, roads, airorts, tunnels, hydro tehnial objets, Other seial uroses of lose rage hotogrammetry are riminology, road aidents, miro hotogrammetry. Terrestrial hotogrammetry is generally assoiated with objets distanes in exess of 300m. Another distintion between two ategories is the fat that in terrestrial hotogrammetry ameras are foused to infinity while it is not the ommon ase in lose range hotogrammetry. This tye of terrestrial hotogrammetry is alled also toograhi terrestrial hotogrametry (some times hototoograhy). This is a siene of surveying in whih the detail is lotted entirely from hotograhs taken at suitable ground stations. The hotograhs in terrestrial hotogrammetry are usually used for toograhi uroses or for terrain modeling. They have large foal distanes and ould be used for great distanes to the objets. Cameras used for roduing terrestrial hotograhs are alled terrestrial ameras or hototheodolites. Phototheodolites are ombination of theodolite and hotogrammetri measuring amera in whih the relationshi between the amera axes and the line of ollimation of the theodolite an be measured. The single ameras used in lose range hotogrammetry ould also be used in terrestrial hotogrammetry (when they are usually foused to infinity). For lose range hotogrammery is usually ossible to determine more aurate the osition and orientation of hotogrammetri ameras. FH-KA - Master ourse Photogrammetry 003

2 Leture /3/003 Deending on the relative orientation of main amera axes we have stereo oule with arallel axes, with onvergent axes (most often oriented to the enter of the objet) and with divergent axes. This last ase is usually alied when we have amera osition inside of the objet. For stereo airs, taken with arallel axes we have normal ase, when axes are erendiular to the base, left or right tilted arallel hotogrammetry. Deending on the sloe of amera axes we have ases of horizontal hotos and sloed hotos (raised or droed). The most ommon use of lose range hotogrammetry is normal ase. There are ameras designed for taking only the normal stereo airs (stereometri ameras). Y A b Y 0 b O B O X x a P x P a Figure 4.. Normal ase The oordinate relations in normal ase are very simle FH-KA - Master ourse Photogrammetry 003

3 Leture /3/003 X Y Z A YA = x B. = A A xa, YA = z, a, a where arallax x, A = x, a x, a (4.) The derivation of error in distane diretion σ Y as a funtion of base-length is shown in the Aendix. The length of base B is seleted from the relation Ymax < B < Y 0 5 min For the tilted arallel ase the amera axes are arallel eah other but they are tilted at the angle Φ. The geometry of this ase an be related to the normal ase with different value of base b. Very often when it is neessary to rodue a model of whole objet the surrounding osition of aturing ameras is alied. In this ase the adjaent ameras are with highly onvergent axes and stereo measurement is not ossible. In this ase the arrangement of ameras is made in suh way that it is a ameras in front of the main faades of the objet. Similar situation is shown on the figure below. (4.) FH-KA - Master ourse Photogrammetry 003

4 Leture /3/003 Y A F b Y 0 F x a O P B F b O X x P Figure 4.3. Geometry of arallel tilted ase a The right station is dislaed in Y diretion on the value B y B = B.os Φ B = B.sin Φ (4.3) x y The geometry of tilted ase is related to normal by substitution b= B (.os Φ x.sin Φ ) (4.4) Substituting in o-ordinate equations we obtain Y X Z A A A b = = = B B B (.os Φ x.sin Φ) (.os Φ x.sin Φ) x (.os Φ x.sin Φ) z For the onvergent ase of taken hotos the amera axes are defleted in the oosite sides in the way that they onverge. This situation is shown on figure 4.3. (4.5) FH-KA - Master ourse Photogrammetry 003

5 Leture /3/003 Y A F F Y av b Y 0 b x a O P B x O a P X Figure 4.3. Convergent ase Some relations between average distane and onvergent angle are given in the Aendix. FH-KA - Master ourse Photogrammetry 003

6 Leture /3/003 Figure 4.4. Cameras surrounding the objet In lose range hotogrammetry is not ossible to define a sale that is equal for the whole objet. The sale is deending on the distane to the orresonding art of the objet. The exression for sale at fixed distane d is defined as follows m b d X = = = (4.6) x' M b FH-KA - Master ourse Photogrammetry 003

7 Leture /3/003 d M = M b b P P Figure 4.5. Cameras with different angle of view Cameras with different frame format (different angle of view) but with equal amera onstant rodue images whit the same sale from the equal distanes. For ameras with equal amera onstants but different distanes to the objet the sales differ. d d M > M b b P P Figure 4.6. Different distane to the objet In this ase the sales for two distanes are as follows d d m = m d d m m M = < < > M (4.7) FH-KA - Master ourse Photogrammetry 003

8 Leture /3/003 Cameras with different amera onstants rodue images with different sale from the same distane. d d M > M b b P P Figure 4.7. Cameras with different amera onstants d d m = m = < m > m M < M (4.8) In ase of usage the ameras with different amera onstants it is ossible to obtain the same sale at the desired objet lane if the aroriate distane to the objet is set. FH-KA - Master ourse Photogrammetry 003

9 Leture /3/003 d d M = M b b P P Figure 4.8. Cameras with different onstants may ensure equal sales The ondition for ameras with different amera onstants to rodue equal sales is the equality of ratios d/. d d d d d m = m = m = m = = (4.9) d The onditions for taking hotos of the objet ould be selet based on the above relations. For every hotogrammetri rojet the aroriate disosition of the ameras must be evaluated. The disosition deends on the goals of the rojet and the required auray. For toograhi hotogrammetry the full over of the area under onsideration is neessary. The amera axes are Usually oriented through the strutural lines of the terrain to ensure maximum visibility from every station osition. The vertial sloe of the amera deends on the terrain height resetively to the amera osition. The amera ositions are usually seleted based on the lanimettri overage of the area of maing. The hek for visibility is made after that. For lose range hotogrammetry the amera ositions are seleted taking into aount different onsiderations. The main goal is to ensure overage of the whole objet with minimal number of stations. From the other side it is neessary to ensure enough number of tie oints between hotograhs. They must be well visible in all the overlaing hotos. Sometimes bad orientation of some of the oints gives as the final result ure estimation for oint auray. FH-KA - Master ourse Photogrammetry 003

10 Leture /3/003 Figure 4.9. Close range hotogrammetry rojet Another roblem is the seletion of ontrol oints. Control oints for lose range hotogrammetry may be natural elements on objets vertexes of the edges, small elements, elements on the drawings or ornaments on the objet. Some time it is ossible to fixed signalized ontrol oints at the suitable ositions. Deending on the objet this is always ossible. After signalizing the objet the roblem is exat ositioning and orientation of ameras. For ositioning the ameras are used traditional survey methods. For orientation are usually used the sulied FH-KA - Master ourse Photogrammetry 003

11 Leture /3/003 instrument for angle measurements. For orientation of hotogrammetri ameras is tyial that usually the angles of theodolite axes are known relatively to the amera axes. This angle is fixed and after that amera is oriented by targeting to seified target on the objet or on the triod. For vertial orientation are usually used bubble levels to ensure base vertial osition of amera axis of rotation during exosure. For near faades are sulied seial adaters that allow to inline amera vertially (uwards or downwards) at the fixed angles ( more often ±30 and ±70gon). When for taking hotos are used non-metri ameras without adaters for reise leveling and orientation the more sohistiated roedures for roessing are alied. In this ase only the observation of ontrol oint in the area of viewfinder is ossible. 4.. Planning and exeuting the Aerial Photogrammetri Projet 4... Tyes of Aerial Photograhy Tyes of aerial hotos are lassified deending on the orientation of amera axes Vertial ase. The amera axes are vertial or near vertial. This is main often used ase. Advantages are: - easy measurements; - normal shae of images and easily reognition; - less hidden ground objets. Oblique ase. The amera axes have greater angles relatively to horizon. The oblique hotograhy an be low-oblique or high-oblique. Advantages are: -overage of large areas; - inreasing base-height ratio. This hotograhy is widely used for military uroses for reonnaissane. Seial ase is horizontal hotograhy. It is usually used for orientation of amera systems. Non frame ameras usage. There are two main ases: - anorami ameras slit is moving erendiularly to the diretion of light. Seial ase of anorami ameras is horizon-to-horizon amera. - slit ameras the slit movement is result of airraft flight. The film is moving synhronous with the rojetion of the ground at the foal distane. FH-KA - Master ourse Photogrammetry 003

12 Leture /3/ General requirements Aerial hotogrammetry is widely used for uroses of maing. The basi oerations in onduting a hotogrammetri maing are: -Photograhy: obtaining suitable hotograhy for maing; - Control: obtaining suffiient ontrol through field surveys and/or extension by hotogrammetri methods; - Ma omilation: the lotting of lanimetri and/or toograhi features by hotogrammetri methods; - Ma Comletion: the refinement of the ma editing in the offie and further, seial surveys in the field; - Final Ma Drafting: the omletion of the ma by drafting/sribing. The first ste, as given in the reeding outline is to reare a omlete lan that will make ossible to start the atual maing oerations and that will guide these oerations as they are arried out. The lan inludes the following essential stes. - Conversion of requirements: region to be maed, the sale at whih it is to be maed, the auray of he final ma, the date by whih the ma should be omleted, the aroximate ost of the rojet; - Gathering of materials and eole for the lanning: hotograhs, mas, survey data, instruments, and ersonnel; - Determining Seifiations and onditions for Oerations: where to establish ontrol, how muh hotograhy is neessary, kind of equiment. - Prearing Final Plans: sheduling, instrutions for surveying, hotograhy, omilation, quality ontrol; - Costing and Relanning: redone the lan until osts are set within limits. The information that is gathered at the seond ste of lanning inludes: a) aerial hotograhs of the region to be maed; b) b) old mas of the region; ) ) survey data showing the loations of horizontal and vertial ontrol in region, the auray of ontrol and its aessibility Planning and exeution of aerial hotograhy rojet (flight lanning) The aerial hotograhy is base uon whih the hotogrammetri rojet is build. The suess of the rojet onsequently deends greatly on the availability of suitable hotograhi overage. FH-KA - Master ourse Photogrammetry 003

13 Leture /3/003 Suitable overage of the rojet deends uon many fators of whih several are of artiular imortane: a) sale of hotograhs; b) overla between exosures; ) otial and mehanial harateristis of the taking amera; d) film base and emulsion tye used; e) date of hotograhy Flight lanning Pratial aerial hotogrammetry is limited to the aroximately normal ase; but the exat normal ase annot be ahieved. The deviations of individual hotograhs from the strit normal ase are, in ratie not more than Dw=±5 gon, DF=±3 gon and Dk=±5 gon. A tolerane of ±% in the flight height is usual. The trak of the airraft an, with visual navigation and good navigation information, be held within ± m in the hotograh sae. The simle geometri relations required for flight lanning are shown 4.9, where flat ground is being assumed. Figure 4.0. Flight lan The relations between main arameters of flight rojet (aording to Kraus) are formulated later on. In formulas and figure 4.0 are used the following symbols. A Distane between flight lines B Base Prinial distane s Image side (to edge) h Flying height above the ground Z Ground height FH-KA - Master ourse Photogrammetry 003

14 Leture /3/003 Z 0 Absolute flying height v Flying seed over the ground L Length of the stri or blok Q Side length of the blok m m Sale of maing The relations between arameters of flight rojet are defined. Table 4. Photo sale number m k. m = m k deends on aaratus Flying height above the ground h= m. Image side in the ground S = sm. Base in the hotograh b = B m Absolute flying height Z0 = Z + h Overla between hotos [%] Side la (%) S B B l =.00 =.00 S S S A A q =.00 =.00 S S Ground area of one hotograh F = S = s. m Base length for l% overla Distane between stris for q% side la l B = S. 00 q A= S. 00 Number of models in the stri L S.( l/50 ) nm = + for l > 50 B Number of hotograhs in the stri n = n + Number of stris in a blok Area of stereosoi model F = ( S B) S n s m Q S = + for q< 50 A m. New area for eah model in a blok F = AB. Time between hotograhs B [ m] t [s] = /0 v [ m/ s] FH-KA - Master ourse Photogrammetry 003 n

15 Leture /3/003 [ ] Largest integer number The values of l and q are usually taken l=60% and q=30%. When GPS ontrol is used for airraft traking it is ossible to derease the values of overla and la but not too muh due to the requirements of trile overlaing in stri and overlaed tie oints between the stris. The value of side la allows for: Errors in holding the trak of the airraft along the stri (~±5%) Variations in lateral tilt Dw (~±5%) Residual, unorreted drift (~±3%) Variations in rotation of the hotograh about its axis (~±3%) Smaller variations in terrain heights Lightening of the image at the edges in eletroni dodging, whih make it imossible to observe stereosoially right to the edges. By satisfying the above onditions it is ossible to remain minimum 0% overage of side la between stris, in whih homologous oints an be found to serve as tie oints between stris, and maing is ossible without gas. Flight lanning is insearably bound u with rojet lanning. The artiular oints to be observed are: The erformane limits of the airraft The ranges f the stereolotter to be used The tye of rodut line ma or hoto ma The ground relief The size of the ma sheets of the finished rodut The auraies required Two methods are used to allow for the ma sheet limits with Very good navigation data are required for aimed hotograhs to ensure that the hotograhs really are aimed stri: aimed single hotograhy or a high overla. A global ositioning system is a very good hel in this task. If a high overla is hosen, usual value of 90% and the best situated hotograhs and stereoloters are then hosen. A navigation lan is drawn u as art of the flight lanning. This an onsist either of enlarged aerial hotograhs or better a good toograhi ma. The navigation lan must show: The area of interest, whih absolutely must be overed by stereoairs; Any obstales of flying; FH-KA - Master ourse Photogrammetry 003

16 Leture /3/003 Any rohibited areas, whih are forbidden for flying or allowed under strit reautions (military training areas, foreign ountries). The requirements to grahial resentation of navigation lan: Area of resentation must be extended at least 5 km at eah end of the stris, for turning of the airraft; The flight line is shown with solid lines over the stris and with dashed lines for manoeuvres. Eah flight line is aomlished with notes on the flying height and ourse (azimuth in degrees) at eah end. Additional information is given on searate sheet. It ontains: -Projet name, urose, dates, -Photo sales, foal length, absolute flying height, overla, side la, -Minimum length of film required and tye of film; Organization details: -agreements on signalisation of oints, -loseness of international boundaries, -flying only under full loud over. The tyial navigation and ersonnel equiment of survey airraft inludes: seial glass of amera ort or remotely oerating amera; navigation instrument is inside with overla regulator; Central disosition of amera orts with ossibilities to lose the doors during take off and landing Good view downwards for the amera oerator and ossibilities for ommuniation; good navigation utility GPS, Doler or Inertial Navigation systems (INS) Flight rew duties: - ilot oarse navigation; - oilot ilot suort - (navigator navigation), - amera oerator fine navigation and amera ontrol Aerial amera equiment Modern aerial ameras are omlex system. A shemati diagram of suh amera is shown below. FH-KA - Master ourse Photogrammetry 003

17 Leture /3/003 Camera yle (min.6-.0 se) inludes: Figure 4.. Camera equiment exosure (with motion omensation), rising the ressure laten, releasing the vauum transort the film, advaned the hoto number, aly the vauum, ress the laten. Modes of exosure: aimed single hotograh by oerator ontrol; serial hotograhs with automati overla ontrol Content of the Viewfinder used for visual ontrol: -field of view with interhangeable frames, deending on objetives; - level bubble; - entral ross of target oint; - set of moving eentri siral for overla ontrol; - entral line for angle orientation and drift ontrol. FH-KA - Master ourse Photogrammetry 003

18 Leture /3/003 Figure 4.. Navigation view-finder If it exists wind during the flight, the airraft trae on the ground does not oinide with the diretion of flight. By that reason the angle orientation of amera is due to be in the oosite diretion (but with the same size as) the angle airraft flight aording to the flight line. The influene of the wind is shown on the next figure (aording to Kraus K., 983) Figure 4.3. Drift omensation FH-KA - Master ourse Photogrammetry 003

19 Leture /3/003 v 0 vetor of own veloity v w vetor of wind v resultant vetor of veloity over the ground Some ameras have searated overla regulator with viewfinder Figure 4.4. Overla regulator Barometri differential height measuring devie (statosoe) The ossibility to exosure the oordinates from navigation system (if ersists) Some ameras have unit for forward motion omensation. Aendixes Aendix The derivation of error in distane diretion σy as a funtion of base-length is shown below. It is derived from the formula for Y oordinate in objet sae. B Y =. (4.0) x The error in Y o-ordinate is funtion of the standard error of the arallax FH-KA - Master ourse Photogrammetry 003

20 Leture /3/003 B. σy =. σ (4.) x The error is estimated for maximal distane beause for it the error is maximal. From this error the value of B an be omuted. ( Ymax ) σ B = (4.) σ The length of base B is seleted from the relation Y Ymax Ymin < B < (4.3) 0 5 The stereo overlaing zone stats at the distane Y 0 from the middle of the base and has wideangle.β. The distane of the vertex of stereo overlaing zone is defined by the equation B Y0 =.ot gβ (4.4) As angle β ould be exressed by hoto size l x and amera onstant, lx / tan β = (4.5) it is ossible to obtain other resentation for Y 0 Y 0. B. = (4.6) l x Aendix The length of base B and average distane Y av with overlaing of k ov are onneted with relation B = ( k ). Y.tan( β +Φ ) + ( k ). Y.tan( β Φ ) (4.7) ov av ov av The minimal distane at whih the overlaing area begins is given by the equation Y 0 = B tan( β +Φ ) + tan( β Φ ) (4.8) FH-KA - Master ourse Photogrammetry 003