نشریه علوم و فنون نقشه برداری
پیاپی 3 (بهمن 1390)

Using stereo cameras for visualization and three-dimensional reconstruction is highly applied, because in addition to the interior orientation,relative orientation parameters are stable during the imaging. Therefore these parameters can be used as stable values in next processing levels for eppipolar resampling in stereo vision, automatic image stitching in creating stereo panorama, and extracting geometry information.In the common methods, to calibrate stereo camera, the exterior and interior orientation parameters for each camera lenses were determined by solving bundle adjustment. After that, the relative orientation parameters of the two lenses were calculated by using the relationbetween the two lenses.This method is not highly persistent,because of the considerable noise in estimation of the exterior orientation parameters.In our method, an improved method to calibrate the stereo cameras is provided and evaluated in which the relative orientation parameters were determined directly to calibrate the stereo cameras using constrained bundle adjustment.The experiments indicated that to calibrate the stereo camera, our method has improved up to 20 percents more than the common method in relative orientation parameters’ standard deviation.

One of the most climatic variations in the cities is the temperature rise due the changes in land use. In the cities the areas covered with vegetation have been replaced by asphalt and concrete paving.Lake of vegetation in the cities usually leads to problems like air pollution and waste of rain water. Therefore measuring the vegetation coverage and its correlation with the land surface temperature is of concern. In this study correlation between NDVI and land surface temperature and correlation between change of NDVI and change of land surface temperature are measured through MODIS images within a time range of 12 years on 14 cities with different climatic conditions in Iran. The correlation between the land surface temperature and the NDVI is higher in day time than night. Since many factors affect the temperature changes in the cities,correlation between change of NDVI and change of land surface temperature from 2000-2011 is weak. By comparing level of this correlation in the cities and their vicinities it was found that this correlation greater as the areas become distanced from the cities.

Recently, Interferometric Synthetic Aperture Radar (InSAR) has proven to be a very effective technique for monitoring and measuring earth surface deformations,such as subsidence, landslide, volcanic and other tectonic deformation. InSAR observations are based on measuring the differences in received phases of SAR images which covers the same area.Almost, any interferograms covers areas where the signals decorrelate, so measurements in these regions are not reliable. This problem is due to temporal and spatial decorrelation and alsodifferences in atmospheric delay between imges. There are two main techniques to overcome the mentioned limitations: Small Baseline Subsets (SBAS) and PersistentScatterer Interferometry (PSInSAR).This paper investigates land subsidence due to ground water exploitation in Tehran Plain by means of PSInSAR. Envisat datasets between 2003 and 2004 are used.To evaluate the results, the InSAR subsidence rate and time series are compared with spirit leveling measurements.

Land and its cover has always been changing and evolving due to various human activities over time. Detecting, Identifying and predicting these changes could be very beneficial in sustainable monitoring and management of land use and cover both in urban and rural areas. Inthis field, to better understand the process of these spatio-temporal changes, cellular automata (CA) models are very common due to their dynamic simple structure and powerful spatial features. It is noteworthy, however, that the conventional cellular models confront many difficulties because of cell size sensitivity and also the inability to consider real spatial objects.On the other hand, novel object-based CA models which have managed to mitigate these problems are very complex and difficult to implement, and therefore, not very practical. This paper presents a hybrid cellular automata (HCA) model as a combination of cellular structure and vector concept. The space is still defined by an organized set of cells, but rasterized spatial objects are also utilized in the structure of transition rules. Particle swarm optimization (PSO) is also used to calculate the urbanization probability of cells based on their distance from development parameters such as road network or major city centers. The proposed model is applied separately to Landsat satellite imagery of the city of Tehran, Iran with 28.5, 57 and 114m spatial resolution, to simulate the urban growth from 1988 to 2010.Statistical comparison of the ground truth and the simulated image derived by the HCA model (for images with 28.5m resolution) shows an accuracy of 83/42 percent (Kappa coefficient),which is greater in comparison to the applied conventional CA model’s result with an 81/13percent accuracy. Moreover, decreasing the spatial resolution by a factor of one-fourth, has reduced the simulation accuracy of the HCA model by 1/19 percent which in comparison to conventional CA model’s 3/04 percent decrease, shows the lower scale sensitivity of the proposed model.

Generalization is a prevalent concept in Cartography to which has been added new aspects such as model generalization with developments in GIS. Increasing demand for tailored and ubiquitous geospatial services like wayfinding, makes the context-aware generalization a noticeable research area in GIScience. Most of the wayfinding services use the network data model as the main spatial data model for their analyses. Whatever data or information that characterizes the situations relevant to users, systems and applications,can be considered as context. A ontextaware service is as a service which can sense user, environment and device’s situations and respond to user requests concerning contexts to fulfill the user`s needs better. From the GIServices perspective, the context of a query could be the location of the device, environmental settings that query is made in, the time, the activity of the user, user`s personal information, the user`s favorites and information needs, the user`s cognitive map of environment, the mode of travel, the purpose of travel and the device’s technological specifications.In this paper, we propose and implement a method for context-aware network abstraction and generalization for presenting routes to the user. In this method, landmarks, POIs, personallymeaningful places and current user location together play the seed role in theabstraction and generalization process.Network Voronoi Diagrams are used in this thesis for network partitioning with aforementioned places as generators. Edges and nodes which are in a voronoi diagram will be abstracted to a node in the next generalized level in the hierarchy.Repeating this procedure will produce other levels of hierarchy, based on selecting most salient generators in each level and use them as generators to form the next level.This hierarchical structure will be used for presenting routes.

Mean sea level in various countries is calculated from spectral analysis of observations tide gauge which it has not enough precision. For the determination of mean sea level the instantaneous sea level heights observed by Topex/Poseidon and Jason-1 satellites during the years 1992 to 2008 (altimetry data) are used.In this research is assumed, the sea surface in addition to periodic tidal variations,changes in long-term exposure (approximately constant), and polar ice melting due to linear movement of tectonic plates. Also in this study The repetitive periodic coverage from satellite altimetry data to prepare time series covering the study area.Here For the modeling of mean sea level (MSL), all the periodic variations of lunisolar and polar tidal origins as well as the linear variations due to melting of icebergs, plate tectonics, and sea currents have to be modeled.This calculates is executed via least squares method for removing tidal variations.Due to long period data, All of known constituents in tidal potential such as M2,S2, K1, O1 … are considered. Mean sea level respect to reference ellipsoid WGS84 during 1992, 1997, 2000, and 2008 is defined.

Due to absorption and scattering by gases and aerosols, the reflected radiance from ground surface changes when passing through the atmosphere before getting captured by the remote satellites. The absolute image atmospheric correction is the prepossessing step that reducesatmospheric effects. These corrections improve satellite image quality and increase processing performance of such images. Many absolute image atmospheric correction methods use radiative transfer code procedures. In this paper, the potential of two well-known code 6S and MODTRAN5 in absolute imageatmospheric correction of TM images was studied. Atmospheric correction results investigated via visual inspection of Top of Atmosphere (TOA) and surface reflectance values were extracted by two methods.Also the quantity of information variation in spectral images was investigated by Entropy, Range and Standard deviation criteria. The results clearly show that correction of atmospheric effects in visible spectrum and infrared spectrum appears with negative and positive signs respectively. Also the differences between utilized codes illustrated in surface reflectance were observed in infrared spectrum. Moreover, both codes (6S and MODTRAN5) improve quality of imageregarding TOA reflectance image with 12% and 23% in Mean Range and 5% and 6% in Entropy respectively.

GPS positioning attained an accuracy level that the residual sources of errors are known as station effects or multipath errors. In fact there are no stations notbeing affected by multipath errors. The socalled errors are fundamental elements in precise positioning and subtle use of high rate GPS. Since the multipath errors are dependent on the GPS satellite geometry and the constellation of that system’s satellites is repeatable, the so-called errors are repeatable too. Techniques for calibration and correction of these errors are based on repeatability of the system constellation. It is assumed that the repeatability occurs based on the sidereal repeat period of satellites; however, the true repeat period of this repeatability varies even for each satellite. The real daily advance of constellation of the GPS satellites can be determined by the broadcast ephemeris. In this paper, the true repeat period and its average are computed, and the average of the periods of ground track of the recent decade is estimated as 23 hours, 55 minutes and 55 second.