6th International Symposium on Mobile Mapping Technology, Presidente Prudente, São Paulo, Brazil, July 21-24, 2009

SMALL-FORMAT DIGITAL : A STUDY INTO STABILITY ANALYSIS OF THE INTERIOR ORIENTATION PARAMETERS THROUGH VARIATION

E. Mitishita *, J. Côrtes, J. Centeno, A. Machado

Department of Geomatics - Federal University of Parana, UFPR - Centro Politécnico - Setor de Ciências da Terra CEP 81531-990 - Curitiba, Paraná, Brazil – [email protected]; [email protected]; [email protected]; [email protected]

Commission V, WG V/1

KEY WORDS: camera stability, camera calibration, georeferencing, low-cost digital

ABSTRACT:

In the last years, small and digital cameras have become a potential tool for photogrammetric applications due to its convenience, availability and quick image acquisition and processing. In addition, the resolution of these cameras has significantly increased while their price decreased. However, to extract accurate and reliable 3D metric information from images, an important condition should be considered: Are the interior and exterior orientation parameters accurate enough for photogrammetric applications? Generally, the camera calibration procedure is performed using a target or a linear test field, regardless of the photogrammetric project that will be later performed. For photogrammetric applications, the camera should be stable and the interior orientation parameters not vary with time. In addition, the exterior orientation parameters of the images should be accurately determined. The exterior orientation parameters can be determined by indirect or direct geo-referencing. Traditionally, using ground control points and bundle adjustment, the indirect method is often performed. The direct method is applied when GPS/INS data are available onboard the platform. Considering airborne photogrammetric mapping, the generally is carried on planes and exposed to different from the one registered during the calibration procedure. Two aspects should be discussed: Did the interior parameters change? Will the changes modify the quality of the derived information? In the paper we try to answer these questions. The digital camera DSC-F828 is calibrated under different temperatures to determine the geometric stability through a great temperature variation. The camera is calibrated at different times, varying the environmental temperatures from close to zero to twenty-five degrees Celsius. A special procedure is used to achieve temperatures close to zero degrees that enable to take good quality pictures. Two external target testfields are used to perform all experiments. The camera was calibrated no less than twice at each temperature. The geometric stability analysis at different temperatures and epochs is presented and discussed. In addition, airborne photogrammetric experiments, using different sets of interior orientation parameters, are performed to stability analysis at different environmental temperatures. Finally some conclusions are drawn from the experimental results, and future recommendations are proposed.

1. INTRODUCTION from collinearity model. Mitishita et al. (2003) used a set of aerial convergent video images over a target test field and Photogrammetry is the science of extracting accurate metric bundle adjustment with self-calibration to compute the IOP of information from imagery. Nowadays, low-cost digital cameras the HITACHI onboard the Robinson R-44 are being used for many photogrammetric applications. An Newscopter helicopter to perform photogrammetric essential aspect of the suitability of these cameras is the applications. Habib et al. (2002), Habib & Morgan (2005) and determination of their internal geometric characteristics, Tommaselli & Telles (2006) used object space straight lines in commonly known as the interior orientation parameters (IOP). a bundle adjustment with self-calibration, considering that any Without this information, the systematic errors in the image deviations from straight line projected in the image space is measurements can not be modeled, and therefore the derived modeled by distortions parameters. Using bundle adjustment metric information in the object space will be degraded in terms with self-calibration and a set of convergent images, Galo et al. of accuracy. Frequently, the interior orientation parameters (2006) calibrated a Multispectral DuncanTech MS3100 – CIR (IOP) are computed by a bundle adjustment with a self- camera to evaluate the quality of 3D reconstruction in the infra- calibration procedure that uses a set of images, geometrically red (IR), red (R) and green (G) spectral regions. Cronk et al. acquired over a calibration test field. (2006) showed a methodology to calibrate low-cost digital camera, using bundle adjustment with self-calibration, a Camera calibration, using self-calibration procedure and low- procedure to measure targets automatically and an approach to cost digital camera, is a research topic vastly worked by compute initial values of the exterior orientation parameters of photogrammetric and vision researchers. There is an the camera stations, without human intervention. extensive number of papers on this topic. Fraser (1997) reviewed the mathematical formulation of self-calibration Together with the quality of IOP estimation, their temporal procedure and discussed the main sources of image deviations stability should be considered for photogrammetric applications

* Corresponding author.

of low cost digital cameras. In regard to camera calibration georeferencing procedure, have strict requirements regarding subject, there is a small number of papers about the stability the stability of the internal characteristics of the camera. In such analysis of low cost digital cameras. This reduced of literature a case, slight changes in the IOP will have a effect on can be attributed to the lack of standards for quantitative the quality of the reconstructed object space. On the other hand, analysis of camera stability (Habib & Morgan, 2005). using EOP from indirect georeferencing procedure, the Commonly, a statistical test is used to verify whether two IOP inaccuracy in IOP can be compensated by EOP estimation. sets are equivalent or not. Due to some uncertainty to perform Considering airborne photogrammetric mapping, the digital the statistical test, Habib et al. (2006) proposed three new camera is generally carried on planes and is exposed to different methodologies for testing camera stability based on the degree temperatures from the one registered during the calibration of similarity between the reconstructed bundles using two sets procedure. Two aspects should be discussed: Did the interior of IOP. Zero Rotation Method (ZROT) fixes two bundles of parameters change? Will the changes modify the quality of the rays in the same position and orientation. It is analogous to derived information? In the paper we try to answer these photogrammetric direct georreferencing. Similar to questions. The digital camera Sony DSC-F828 was calibrated photogrammetric bundle adjustment that fixes position of under different temperatures to determine the geometric camera station by GPS determination, in the Rotation Method stability through a great temperature variation. Varying the (ROT), the bundles can rotate relative to each other to achieve environmental temperatures from close to zero to twenty-five the best fit. In the Single Photo Resection Method (SPR), the degrees Celsius, the camera was calibrated no less than twice at bundles can rotate and shift in order to assure the best fit at the each temperature. The geometric stability analysis at different object space. It is similar to photogrammetric indirect temperatures and epochs is presented and discussed. In georreferencing. addition, airborne photogrammetric experiments, using different sets of interior orientation parameters, the stability analysis at Machado et al. (2003) performed the stability analysis of the different environmental temperatures are performed. Sony DSC-F717 digital camera. The camera was calibrated three times over two months of regular use. The analysis from The following section presents the material and methods for three set of IOP resulted that they can be considered evaluation of geometric stability of a low cost digital camera approximately equal. Therefore, the camera was considered through ambient temperature variation. The last two sections stable over the test period. In Habib & Morgan (2005) the Sony cover results obtained in the performed experiments, as well as, DSC-F707 digital camera was calibrated two times over ten conclusions and recommendations for future work are showed. months of regular use to perform the stability analysis. The IOPs from two calibrated sessions were considered almost identical. Habib et al. (2006) checked the stability analysis of 2. MATERIALS AND METHODS the 14n digital camera, using ZROT, ROT and SPR methodologies. The camera was calibrated four times over six 2.1 Testfields months of regular use and the four sets of IOP were compared among them. Using the ZROT method, no combination of two Two target testfields were used to perform the proposed IOPs was considered equal. Using the ROT or SPR method in a research. The first is a two-dimensional testfield with forty-five big gradient relief, two combinations were considered equal. targets that were precisely surveyed using a total station. This All combinations of IOP were considered equal when the SPR testfield was established on a large wall on the side of a method was used in a flat relief. Therefore, the camera was building, which is shown in Fig. 1-a. The second is a three- considered stable only over this condition. Wackrow et al. dimensional testfild built on a support wall which is shown in (2007) verified the stability and manufacturing consistency of Fig. 1-b. Twenty-seven targets were precisely surveyed using a seven Coolpix 5400 digital cameras over a year. The terrestrial laser scanner. The accuracies of the 3D target cameras were calibrated four times over this period. The coordinates in both testfields are close to one millimetre. temporal stability was performed by comparing 3D coordinates of check-points determined by photogrammetric intersection and DEM generation, using different sets of IOPs. To assess the manufacturing consistency the same methodology was used, but the photogrammetric process were performed using images from one camera with IOP from another. Using images of a test field that were taken from a 1.5 m of distance, the performed experiments yield millimeter accuracy, whichever combination of image sets and IOP was used. Rieke-Zapp et al. (2009) reported that latest digital camera models have included some a) two-dimensional testfield b) three-dimensional testfield features such as vibration for removal of dust particles Figure 1. Testfield used in this research and sensor movement to reduce the effect of camera shaking during the image acquisition. These features cause possible instability of the sensor position, which is not allowed in 2.2 Evaluated Camera Photogrammetry. Rieke-Zapp et al. (2009) analyzed the performance of eleven digital cameras to derive object The Sony DSC-828 digital camera was used to carry out this measurements in the object space. In the calibration process, the research, which is shown in Fig. 2. The CCD sensor has 8.0 parameterization of geometric instabilities using a model of an million of effective . The CCD type is 2/3” with the size: image variant for interior orientation improved the results for diagonal equal 11.00 mm; width equal 8.800 mm and height most cameras. equal 6.600 mm. The size is 0.0027 millimeter. The images used on this research have 3264 x 2448 pixels. According to Habib et al. (2006), photogrammetric processes, using exterior orientation parameters (EOP) from direct

analysis in the stability experiments. Three aerial images covering a small urban region with six pre-signalized control points, which is shown in Fig. 4, is be used. The expected planimetric and vertical accuracy based on the average flying height, baseline, image pixel size and principal distance are used to analyze the accuracy of the obtained results from performed bundle adjustments. The best estimation of EOP from indirect bundle adjustment experiments is be used to simulate direct (GPS and GPS + INS) bundle adjustment experiments. From the results of the experiments that were performed with different sets of IOP, the stability of the camera over a great temperature variation is evaluated.

Figure 2. Sony digital camera used in this research

2.3 Camera Calibration

To perform camera calibration on this research, the bundle adjustment with self-calibration is used. The principal distance, the coordinates of the principal point, and the parameters of radial and decentring lens distortions are the Interior Orientation Parameters (IOP) considered. Generally, twelve images are taken of the testfield. The principal distance is fixed manually at infinity and the convergent images are Figure 4. Example of image used in the experiments acquired from three different camera stations with four roll angles each (0°, ±90° and 180°). The camera is calibrated many times, varying the environmental temperatures from 3. RESULTS AND DISCUSSION approximately zero to twenty-six degrees Celsius. A special procedure, used to achieve temperatures close to zero degrees, 3.1 Camera Calibration allowed the camera to take good quality pictures of external target testfields. First, the Sony camera was wrapped with silica To perform this research, the Sony camera was calibrated six gel and kept, approximately, for twelve hours in the freezer. To times over five months. In the first and second cold calibrations, keep the lens from getting blurry, it was put inside a performed in January 22/2009 and March 22/2009, the camera polystyrene box with ice plates. The box, which is shown in was kept inside the freezer, approximately 12 hours and the Fig. 3, has a small hole allowing picture capture. images of the two-dimensional testfield were taken. The temperature inside of the polystyrene box was close to three degrees Celsius. Figure 5 shows an example of an image that resulted from this methodology.

Figure 3. Polystyrene box used to take pictures

2.4 Stability Analysis Figure 5. Example of image used in cold calibration

The stability analysis aims to verify if the internal In the third, fourth, fifth normal calibrations, performed in characteristics of a camera change significantly to modify the December 17/2008, January 21/2009 and June 17/2009, the accuracy of derived information from image, over a time used two-dimensional testfield was used again. The external period. Generally, the analysis is carried out by comparing the temperature was close to twenty-five degrees Celsius when the performance of two sets of IOP to reconstruct the bundle of images were taken during the third and fourth calibrations and light rays that was measured on the image, similar at the fifteen degrees Celsius during the fifth. The Figure 6 shows an moment of . In this research, the direct and indirect example of an image from the two-dimensional testfield, used georeferencing of images by photogrammetric bundle in this research. During the sixth normal calibration, performed adjustment, using different sets of IOP, is used to perform the in January 30/2009, the three-dimensional testfield was used

and the external temperature was close to twenty-five degrees through a simple visual analysis. Considering the calibrations Celsius when the images were taken. Twelve images were performed, only the parameter k1 was deemed significant to the generally used to perform the calibrations. The target images model of radial lens distortion. The k1 parameter value reveals were measured by manual monocular process. The bundle that the Sony camera has big radial lens distortion on the image adjustments with self-calibration were performed, using one borders. The second cold calibration estimated the biggest k1 pixel (0.0027 mm) for the standard deviation of the image parameter and the fifth normal calibration the smallest k1. The coordinates and one millimeter for the standard deviation of the Figure 7 shows the dimension of radial lens distortion from six targets coordinates on the object space. The main results from performed calibrations. Other IOPs from normal calibration can the performed calibrations are shown in table 1. be considered as almost similar as the ones from the cold calibrations. The correlation among IOP parameters, related with the estimation process via bundle adjustment with-self calibration, complicates the simple numeric analysis of the parameters values.

Figure 6. Example of image used in normal calibration

The results showed in Table 1 reveal a considerable variation on estimated IOPs from different calibrations. The first cold calibration estimated the smallest values of principal distance and smallest coordinates of principal point; the second Figure 7. curves of radial lens distortion calibration, using similar environmental temperature, estimated values close to those that were estimated in the normal calibration. Therefore it is impossible conclude if low temperature introduces significant modification on the IOPs

-2 Calibration c (mm) σc (mm) xp (mm) σxp (mm) yp (mm) σyp (mm) k1 (mm) σk1 (mm ) Cold_first 7.300 0.014 -0.042 0.008 0.018 0.010 -2.5909e-3 9.2082 e-5 Cold_second 7.350 0.017 -0.019 0.012 0.003 0.010 -2.7737e-3 1.3751 e-4 Normal_third 7.346 0.015 0.005 0.011 0.002 0.010 -2.7208e-3 5.4369 e-5 Normal_fourth 7.346 0.005 -0.026 0.004 0.013 0.004 -2.2593e-3 2.1791 e-5 Normal_fifth 7.338 0.005 0.015 0.004 0.014 0.004 -2.1757e-3 2.3243 e-5 Normal_sixth 7.350 0.013 -0.029 0.008 0.004 0.008 -2.4320e-3 8.2529 e-5 Mean 7.338 0.019 -0.016 0.022 0.009 0.007 -2.5478e-3 2.1718e-4

Principal distante (c); Coordinates of principal point (xp ,yp); Radial lens distortion; Standard deviation (σ) Table 1. Sets of IOP from Sony camera calibrations

3.2 Stability Analysis from photogrammetric experiments are computed by the root mean square errors. To perform the stability analysis of the Sony digital camera at different temperatures, three aerial images were used. The images were taken in June 15/2009 with 80% overlap. The 3.2.1 Indirect Georeferencing small urban region, which is shown in Fig. 4, covered by the images has six pre-signalized control points. The flight height is The bundle adjustment was performed to compute the exterior close to three hundred meters, resulting in image-ground orientation parameters of three images. The images from pre- resolution close to thirteen centimeters. Based on the average signalized targets were measured by manual monocular process. flying height, the average baseline, the principal distance of the Using the estimated sets of IOP from the calibration sessions, camera and two image pixels size (0.0054 mm), the expected six sets of image coordinates were refined. Using five control- planimetric and vertical accuracies are 0.26 and 0.80 m, points, one check-point, the standard deviation of the image respectively. These values will be used to verify the accuracy coordinates equal to one pixel (0.0027 mm) and five centimeter achieved in check-point analysis from all photogrammetric for the standard deviation of the targets coordinates on the experiments performed with different IOPs. The sets of IOP are object space, six bundle adjustments were performed. considered similar when the planimetric and vertical accuracies from the photogrammetric experiments are equal or less than The outcome analysis from the six performed bundle the expected accuracies. The planimetric and vertical accuracies adjustments, showed in Tables 2, 3 and 4, yielded important results:

- The root mean square errors and variance component cold_first bundle adjustment experiment, the obtained results computed from image control points and object coordinates are quite similar to the normal_fourth experiment. This result residues reveal similar internal precisions in four performed proves that the correlation among IOP complicates the visual bundle adjustment; comparison among two set of IOP values that were estimated - In second_cold and third_normal bundle adjustments, the via bundle adjustment with-self calibration; results of the root mean square errors and variance component - Considering the abovementioned about the obtained results are slightly bigger than those that were computed in other from the six bundle adjustment experiments, it is clear that the bundle adjustments; sets of IOP from the six performed calibrations are not equal. - In the same way, the planimetric and vertical discrepancies Did the variation change significantly the results from the from the check-point analysis show slightly smaller external performed bundle adjustment? In the performed experiments, accuracies in the second_cold and third_normal bundle the vertical discrepancies and the majority of planimetric values adjustments results; are less than the expected accuracies. Only two planimetric - The best results of the internal and external bundle adjustment discrepancy values are slightly greater than the planimetric accuracies were found in the normal_sixth and normal_fifth expected accuracy. Considering these results, it can be admitted experiments. The set of IOP used in the normal_sixth that the variations of the IOPs from the six performed experiment was estimated from the calibration process that used calibration did not change significantly the obtained results the 3D testfield; the set of IOP, used in normal_fith experiment, from the six bundle adjustment experiments. Therefore, for the was estimated from the calibration process performed one day photogrammetric bundle adjustment application (indirect after the aerosurvey; georeferencing), the Sony digital camera that was evaluated in - Considering the calibration results, the maximum this research can be considerable stable, even with the great displacements from mean principal distance and mean principal variations of temperature among the performed calibrations. point values were found in the cold_first calibration but in the

Bundle Control points residues Discrepancies Adjustment Image coordinates (mm) Object coordinates (m) Check-point (m) 2 IOP Set Rmse (x) Rmse (y) Rmse(P) Rmse(V) D(P) D(V) σ0 Cold_first 0.001 0.001 0.029 0.013 0.275 0.313 0.988 Cold_second 0.002 0.002 0.038 0.017 0.300 0.458 1.537 Normal_third 0.002 0.002 0.036 0.016 0.355 0.342 1.376 Normal_fourth 0.001 0.001 0.024 0.011 0.212 0.293 0.774 Normal_fifth 0.001 0.001 0.015 0.004 0.123 0.103 0.431 Normal_sixth 0.001 0.001 0.015 0.007 0.077 0.060 0.455 2 Rmse : Root mean square error; P: Planimetric; V: Vertical; σ0 = Variance component of unit of Table 2. Results from performed bundle adjustment experiments

Image Xo (m) σXo (m) Yo (m) σYo (m) Zo (m) σZo (m) 1 676619.301 1.102 7188036.012 1.309 1188.388 0.920 2 676648.961 0.539 7187964.858 0.769 1192.531 0.768 3 676673.658 0.424 7187900.752 0.954 1195.546 0.662 Table 3: Mean coordinates of the images position station and their stand deviations computed from the six bundle adjustments results

Image ω˚ σω˚ Φ˚ σφ˚ χ˚ σχ˚ 1 7.650 0.3051 -1.026 0.2647 297.953 0.0318 2 9.509 0.0549 2.017 0.1343 297.548 0.0118 3 10.430 0.1185 2.236 0.0231 297.031 0.0102 Table 4. Mean values of rotation angles and their stand deviations computed from the six bundle adjustments results

3.2.2 GPS-Aided Aerial Triangulation bundle adjustment experiment, were considered of errors and the absolute constraints were used. One pixel (0.0027 mm) The same three images, applied in the indirect georeferencing and five centimeter were the standard deviations for the image experiment mentioned above, were used in this experiment. and object coordinates used in all six experiments. The main Since no GPS/INS information were available to compute the results from the performed experiments are shown in table 5. position and orientation of three images, the estimated exterior orientation parameters from the Normal_sixth bundle The results from Normal_sixth experiment are quite obvious adjustment were used to perform the stability analysis of the since it was performed with the same data that was used to Sony digital camera in GPS-aided aerial triangulation process. compute the coordinates of the image position stations. In other The best accuracy in the performed bundle adjustment performed experiments, the planimetric Rmse values computed experiments was the reason to use the Normal_sixth EOPs from check-point discrepancies are greater than the expected values. To perform the GPS-aided aerial triangulation planimetric value. Considering the vertical accuracy, most of experiment, one pre-signalized point was used as control point the Rmse values, computed from check-point discrepancies, are and five were used as check points. The coordinates of the quite within the expected vertical accuracy. The Rmse (x) and images’ position station (Xo,Yo,Zo), from the Normal_sixth Rmse (y) values computed from image coordinates and

variance component values did not reveal the accuracy level of can be concluded that the Sony digital camera that was tested is the performed experiment. Analyzing only the internal accuracy instable, so it is not well suited for this kind of application. of the performed experiments, it can be assumed that the IOP Comparing the obtained results from GPS aided aerial sets are similar to the IOP set from Normal_sixth. On the other triangulation experiments versus the indirect georeferencing, it hand, if the external accuracy from check-point analysis is not difficult to conclude that in the GPS aided aerial considered, the sets of IOP used in the performed experiments triangulation more accurate IOP are required. are not similar to the IOP set from Normal_sixth. Therefore, it

GPS aided aerial Residues Discrepancies Check-points triangulation Image coordinates (mm) Object coordinates (m) 2 IOP Set Rmse (x) Rmse (y) Rmse (P) Rmse (V) σ0 Cold_first 0.001 0.001 1.340 0.665 0.433 Cold_second 0.002 0.002 0.720 0.815 1.288 Normal_third 0.001 0.001 0.769 1.002 1.093 Normal_fourth 0.001 0.001 0.378 0.401 0.493 Normal_fifth 0.001 0.001 0.646 0.881 0.967 Normal_sixth 0.001 0.001 0.080 0.280 0.302 2 Rmse : Root mean square error; P: Planimetric; V: Vertical; σ0 = Variance component of unit of weight Table 5. Results from performed GPS aided aerial triangulation experiments

3.2.3 Direct Georeferencing proving that the direct georeferencing method requires more accurate IOP. Considering the results from this and the previous A simulated direct georeferencing experiment was performed to experiments, the fourth set of IOP is the most similar to the evaluate the stability analysis of the Sony digital camera for this sixth set. According to the values of variance component from kind of application. In the direct georeferencing experiment, the this and previous experiments, the second set of IOP is the most six exterior orientation parameters are fixed in the bundle different; considering the discrepancies from check-points, the adjustment procedure. The same data, utilized in the GPS aided third set of IOP is the most dissimilar. Assuming that the EOP aerial triangulation experiment, was used here. The coordinates from the six bundle adjustment experiment are perfect, the of the image position stations (Xo,Yo,Zo) and rotation angles obtained results from direct georeferencing and GPS aided values (ω, φ, χ) from the Normal_sixth bundle adjustment aerial triangulation proved that no available set of IOP is similar experiment, were considered free of errors, thus the absolute to the sixth, to produce the same accuracies that were found in constraints were used. Six check-points were used to perform the sixth experiment. Therefore, the Sony digital camera that the accuracy analysis of the six experiments. The main results was tested is not stable enough or the camera calibration from the performed experiments are shown in table 6. procedure did not estimate the accurate sets of IOP for this kind of photogrammetric applications. In addiction the obtained In general terms, the obtained results in this experiment are results did not prove that the geometric instability of the camera equivalent to those from the previous experiment. The obtained was caused by the variation of environmental temperature. accuracies from the performed experiments are lower than those computed from GPS aided aerial triangulation experiments,

Direct Residues Discrepancies Check-points Georeferencing Image coordinates (mm) Object coordinates (m) 2 IOP Set Rmse (x) Rmse (y) Rmse (P) Rmse (V) σ0 Cold_first 0.001 0.002 0.822 2.115 0.916 Cold_second 0.002 0.003 0.229 1.529 2.141 Normal_third 0.002 0.003 1.070 1.812 1.924 Normal_fourth 0.001 0.002 0.378 0.807 0.615 Normal_fifth 0.002 0.002 1.718 0.528 1.285 Normal_sixth 0.001 0.001 0.047 0.169 0.194 2 Rmse : Root mean square error; P: Planimetric; V: Vertical; σ0 = Variance component of unit of weight Table 6. Results from performed direct georeferencing experiments

4. CONCLUSION AND RECOMMENDATION FOR in four calibrations, the temperature was close to twenty-five FUTURE WORK degrees Celsius. Two and three-dimensional testfields were used in the bundle adjustment with self calibration procedures. The aim of this research was the evaluation of geometric The stability analysis was performed via photogrammetric stability of a low cost digital camera when exposed procedures that used different sets of IOP. Three aerial images environmental temperature variations. The digital camera Sony were used in indirect and direct georeferencig. Considering the DSC-F828 was evaluated six times over five months. In two results obtained in the experiments, the following specific calibrations, the temperature was close to zero degrees Celsius; conclusions have been drawn:

The Sony digital camera that was used in this research is FRASER, C. S., 1997. Digital camera self-calibration. ISPRS geometrically instable. The values of IOP from the six Journal of Photogrammetry and Remote Sensing, 52(4): 149– performed calibration are different. The experiment performed 159. did not prove that the great variation of environmental temperature that was used changes significantly the values of GALLO, M., TOMMASELLI, A. M. G., HASEGAWA, J. K., IMAI, N. IOP. N., 2006. Registration analysis and inner calibration of a three CCD multispectral frame camera, In: EuroCOW 2006 For the expected planimetric and vertical accuracies used in this International Calibration and Orientation Workshop, research, the sets of IOP from six calibrations were similar to Castelldefels, Spain, 25-27 Jan. (proceedings on CD-ROM) perform indirect georeferencing, so the Sony digital camera used in this research can be considered stable. The changes of HABIB, A., MORGAN, M., LEE, Y., 2002. Bundle Adjustment IOP were compensated in the EOP estimation. On the other with Self-Calibration using Straight Lines, The hand the sets of IOP were not similar for the GPS aided aerial Photogrammetric Record, 17(100):635–650. triangulation and the direct georeferencing experiments. For these photogrammetric applications, the Sony digital camera HABIB, A. AND MORGAN, M., 2005. Stability analysis and was considered instable or the camera calibration process, used geometric calibration of off-the-shelf digital cameras. in this research to compute the IOP, could not estimate Photogrammetric Engineering & Remote Sensing, 71(6): 733– accurately the sets of IOP. Therefore, direct georeferecing 741. requires accurate IOP. HABIB, A., PULLIVELLI, A., MITISHITA, E., GHANMA, M. and The performed experiments proved that it is impossible to EUI-MYOUNG KIM, 2006. Stability analysis of low-cost digital perform stability analysis through the simple comparison of sets cameras for aerial mapping using different Georeferencing of IOP, due to the correlation among parameters in the bundle Techniques. Photogrammetric Record Journal, 21(113): 29-43. adjustment with self calibration. For example: in the first calibration process, the principal distance and the principal MACHADO, A. M. L., MITISHITA, E., SANTOS JR, R. L., BARBOSA, point coordinates values had great shift from the mean values F. P., 2003. Verificação da estabilidade geométrica dos but the bundle adjustment experiment with this IOP did not find parâmetros de calibração de uma câmera digital de pequeno the most different accuracies values. formato Sony-F717. In: Mitishita, Edson Aparecido. (Org.). Série em Ciências Geodésicas – Novos desenvolvimentos em Considering the six bundle adjustment experiments performed Ciências Geodésicas. Curitiba, v. 3, p. 292-309. ISBN: 85- with different set of IOP, good accuracies were obtained in the 88783-04-5. two experiments. The first used the IOP set computed from the tridimensional testfield; in the second, the IOP set was MITISHITA, E., MACHADO, A. M. L., SILVA, V. F., TREVIZAN, S. computed using two-dimensional testfield and the calibration J., SIKORSKI, J, 2003. Desenvolvimento de técnica de images were taken one day after the date that the three aerial mapeamento planimétrico cadastral de rodovias utilizando-se de images, used in the indirect georeferencing, were taken. On the monorrestituição, imagens digitiais provenientes de câmera de other hand, the similarity analysis of two IOP sets via direct vídeo e helicóptero. In: Mitishita, Edson Aparecido. (Org.). georeferencing did not prove that the two sets of IOP Série em Ciências Geodésicas – Novos desenvolvimentos em aforementioned are the most similar. Therefore, future research Ciências Geodésicas. Curitiba, v. 3, p. 227-245. ISBN: 85- will be done to try to answer two questions: Do the three- 88783-04-5. dimensional testfield provide more accurate IOP estimation? Are the IOP computed via on-the-job calibration more WACKROW, R., CHANDLER, J. H., BRYAN, P., 2007. Geometric accurate? consistency and stability of consumer-grade digital cameras for accurate spatial measurement. Photogrammetric Record 22 (118), 121_134. ACKNOWLEDGMENTS RIEKE-ZAPP, D., TECKLENBURG, W., PEIPE, J., HASTEDT, H., We would like to thank the two Brazilian governmental HAIG, C., 2009. Evaluation of the geometric stability and the agencies CNPq (The National Council for Scientific and accuracy potential of digital cameras- Comparing mechanical Technologic Development) and CAPES (The Coordinating stabilisation versus parameterisation. ISPRS Journal of Agency for Advanced Training of High-Level Personnel) for Photogrammetry and Remote Sensing, 64(2009): 248–258. their financial support of this research. TOMMASELLI, A. M. 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