Amir Hosein Shokri; Saied Sadeghian
Abstract
Introduction Recently, cadastre has become a suitable platform for global partnership in management of land and its assets. Due to ever- increasing population, spatial organization of citiesis considered to be one of the most important issues in national development planning. This indicates the necessity ...
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Introduction Recently, cadastre has become a suitable platform for global partnership in management of land and its assets. Due to ever- increasing population, spatial organization of citiesis considered to be one of the most important issues in national development planning. This indicates the necessity of using 3D land information systems since theenvironment, quality, ownership and other benefits of lands do not only change horizontallyany moreand height is also a decisive and vital factor.Therefore, 3D cadastreis used as abasis for integrating information into a complete and efficient information storage system. This system is usedtomanage scarce land resources and plays a key role in achieving future legal and managerial success in the field ofreal-estate. Designing and implementing a system capable of displaying the third dimension (height) is very complex. Common methods of producing 3D cadastral models include land surveying, classical aerial photogrammetry, high-resolution satellite imagery, and so on. Recently, the advent of drones has provided a suitable platform for large-scale cadastral mapping. Collecting high resolution images, processing withstructure from motion(SFM) method, multi-stereo vision (MSV), and dense 3D point cloud with a high resolution of about a few centimeters are the main advantages of these tools. Recentstudies in this field indicate high capabilities of UAV-based photogrammetry method for the production and updating of cadastral maps. Materials and Methods Due to the applied nature of the present study, guideline for the spatial information production using photogrammetric method published by Tehran Municipality and other Surveying and Mapping guidelines published by the National Cartographic Center of Iran have been used to produce 3D cadastral modeland reach relatively real results. The study area is Khosban village in MiyanTaleqan rural district, in the central district of Taleqan County, Alborz Province, Iran. Necessary information was collected using an eBee Plus survey drone with a SODA camera (designed for professional photogrammetric applications). Besides, exterior orientation parameters were measured using the preciseinertial measurement unit (IMU), global navigation satellite system (GNSS) Antenna withreal-time kinematic (RTK) and post-processing kinematic (PPK) techniques and triangulation was performed using these parameters. To increase the accuracy, reduce hidden areas and achieve more accurate 3D models, 75%longitudinal and transverse overlappingwere considered for the images. Image processing was performed using Pix4dmapper and Metashape software and products such as orthomosaic, dense 3D point cloud, and digital surface model were produced. To prove thegeometric accuracy of triangulation, 8 ground control points were used, and32 checkpoints were also used for the final evaluation of 3D models. Results and Discussion 3D cadastre implementation was performedin the present paperusing UAV based photogrammetry without any ground control points. According to the results of triangulation, the maximum root mean square error in the X-component was reported 3.21 cm, the Y-componentwas reported2.86 cm, and the Z-component was reported 3.96 cm using Pix4dmapper and Metashape software. Moreover, 32 sample checkpoints were used for the final evaluation of the 3D models and data collected from these points were compared with the reference data. Results indicated the occurrence of maximum root mean square error in the horizontal components (X, Y) of 0.2 and 0.21 meter respectively, and 0.27 meter in the height component (Z). A correlation coefficient of about 1 represents high geometric accuracy of the 3D models produced using UAV based photogrammetry. Conclusion 3D cadastre can be used as a tool for improving land management and related issues. Due to structural complexity and ownership issues,most developed countrieshave not yet fully implemented 3D cadastre. However, these countries are always looking for ways to achieve such a system. So far in our country, the issue of 3D cadaster has only been pursued in academic studies and no practical stephas been taken to implement this system. Unfortunately, technical dimension and preparation of 3D models are only a part of 3d cadastre and legal issues occurring due to insufficient understanding of the third dimensionand its complexity alsolead to failure in the implementation of 3D cadaster.
Saied Sadeghian; Asghar Milan Lak; Hamed Ahmadi Masine; Roohollah Karimi
Abstract
Extended Abstract
Introduction
Applying GPS/IMU data in aerial triangulation has increased the strength of photogrammetric block and reduced the number of ground control pointsneededfor block adjustment. Systematic errors in data used fortriangulation reduce the accuracy of the process and make ...
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Extended Abstract
Introduction
Applying GPS/IMU data in aerial triangulation has increased the strength of photogrammetric block and reduced the number of ground control pointsneededfor block adjustment. Systematic errors in data used fortriangulation reduce the accuracy of the process and make ground control pointsnecessarydespitetheexistenceof GPS/IMU data. Therefore, reducing systematic errorsin data naturally increases the accuracy of triangulation and reduces the number of ground control points required forblock adjustment andthe number of crossstrips used to eliminate systematic errorsin GPS data.
Materials
Digital images captured by the National Cartographic Centerof Iran from an area in Fars province usingUltraCam-Xpcamera in2010 were used in the present study to investigate the roleof self-calibration parameters in the reduction of ground control points and cross strips requiredfor block adjustmentin aerial triangulation. The intended block consists of 58 images and four strips; two of which are cross strips. Control points in this block include eight horizontal control points, eight vertical control points and eight full control points. Each image has a dimension of 11310 by 17310 pixels, a pixel dimensionof 6 microns, afocal length of 10500 microns, an end lap of 70%, and a side lap of 30%. Theregion has an average elevation of 760 m. Given the focal length, flight height and pixel dimensions, ground resolution is around 12 centimeters. Each image covers anarea of 2077.2 mlength and 1357.2 mwidth on the ground.
Methodology
The present study investigates theroleof self-calibration parameters, such as elimination of systematic error in GPS/IMU data and image sensor,in increased accuracy oftriangulation, and reduced number of ground control points and cross strips required for block adjustment. To reach this aim, optimal self-calibration parameters are determined using a genetic algorithm and the identified parameters are used in the bundle block adjustment. Variance components estimation method was used to solve the problem of equationsinstability. This method not only stabilizes the equation, but also determines the optimal weight matrix during the adjustment process.
Results and Discussion
Since images at a scale of 1:2000 were used in the present study, maximum RMSE equals 60 cm and maximum residual errorsequal 1.2 m. Using additional parameters to eliminate systematic errors results in an acceptable maximum error at the control points, but absence of additional parameters results in an unacceptable maximum error at the horizontal and vertical control points even in the presence of crossstrips. In addition to the evaluation of horizontal and vertical errors at the ground control points, horizontal and vertical RMSE of the checkpointsare also used to evaluate the geometric accuracy of aerial triangulation. Again, applying additional parameters keeps the RMSE at a much lower level than the accepted limit, while absence of additional parameters results in a horizontal and verticalRMSE higher than the accepted limit even in the presence of cross strips. It should be noted that using cross strips reduces RMSE at the vertical component.
Conclusion
Results indicated that using self-calibration parameters and reducing errorsin data used for the adjustment process decreases the number of control points and cross strips required for block adjustment.Using optimal self-calibration parameters(even in the absence of control points) resultsin a maximum RMSE of 0.143 m at the checkpoints, while absence of these parameters results in a maximum RMSE error of around one meter with or without cross strips. Genetic algorithm is capable of determining optimal self-calibration parameters. It is also capable of optimizing nonlinear functions. Therefore, it is not necessary to linearize the equations before determination of self-calibration parameters, which reduces the amount of necessary calculations. Variance components estimation can also be used along with the bundle block adjustment method to stabilize the equations and determine the optimal weight matrix. As a result, it is suggested to take advantage of these three methods, i.e. block adjustment, stabilization and optimal weight matrixdetermination, simultaneously.
Asghar Hosseini; Zahra Azizi; Saeed Sadeghian
Abstract
Introduction LiDAR (Light Detection and Ranging) employs pulse models which penetrates vegetation cover easilyand provides the possibility of retrieving data related to Digital Terrain Model (DTM).Pulses sent by the Lidar sensorhitdifferent geographical features on the surfaceground and scatter inall ...
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Introduction LiDAR (Light Detection and Ranging) employs pulse models which penetrates vegetation cover easilyand provides the possibility of retrieving data related to Digital Terrain Model (DTM).Pulses sent by the Lidar sensorhitdifferent geographical features on the surfaceground and scatter inall directions. Distance to the object is determined by recording the time between transmitted and backscattered pulses and by using the speed of light to calculate the distance traveled by the small portion of pulses backscattered. Most LiDAR receivers at least record the first and last backscattered pulses. The first backscattered pulses are used to produce Digital Surface Models (DSMs) and the last ones are used to produce DTMs. Despite the fact that these data can provide a valuable source for DTM generation, the volume of vegetation (vegetation density) in forest areas reducesthe accuracyof DTMs. Onthe other hand, ground surveying of forest areas is rather expensive and time consuming, especially in largerforests. Aerial images are also used as a source for DTM generation, but this approach requires a 60–80% overlap between images which along with canopy height reduce the potential of this method for DTM generation. Also, low spatial resolution of satellite images collected from forest areas increases errors in DTM generation to a large degree. The present study investigates the accuracy and precision of DTMsproduced from LiDAR data in a forest area. Furthermore, the effect of different methods of filtering and DTM interpolation was explored. Different methods of DTM generation were also closely analyzed and evaluated. Materials & Methods The case study area is located in Doroodforests, a part of Zagros forests, in the southeastern regions of Lorestan province in Iran (48°51’19’’E to 48°54’31’’E and 33°19’21’’N to 33°21’15’’N). Minimum and maximum altitude above sea level were 1143 and 2413m, respectively. The study area covers 100 hectares of mountains with an average slope of 38%. Approximately 50% of the area is covered by forests in which Brant’s oak (Quercusbrantii Lindley) is the most frequent species. LiDAR data were collected by the National Cartographic Center of Iran (NCC) in 2012 using a Laser scanner system (Litermapper 5600) fixed on an aircraft flying at an average altitude of 1000m. LiDAR data consisted of the first and last returns (backscattered pulses), distance and their intensity value. Collected data had an irregular structure and included an average of more than four points per square meter. A DTM was produced using a two-step filtering. First, a morphological filter removed most of non-ground points, and then a slope-based filter detected remaining points. Inforest areas with rough-surface, DTM was producedthrough processing ofLiDAR data with statistical methods likekriging and inverse distance weighting (IDW). These methods apply third and fourth power to detect and remove non-ground points. To assess the accuracy of DTMs produced by different approached, 5 percent of the LiDAR point cloudswererandomly separated as the test data. Amongst these data sets, 62 points with a suitable dispersion were selected and measured using a GPS-RTK. An error matrix, along with accuracy indices (including correlation and Root Mean Square Error (RMSE)) were calculated based on these data. Results & Discussion Results indicated that 44-degree slope is the best threshold for isolation of non-ground points and inverse distance weighting (IDW) is the best third power interpolation method with the highest correlation (0.9986) and the lowest RMSE (0.204 meter). Amongst the filtering methods, slope-based filter used for separation of ground and non-ground points had the best performance. Since this filter combines two parameters of slope and radius, it can remove cloud points related to the vegetation cover and results in high efficiency for steep forest areas. Slope-based filter is suitable for processing of near-surface vegetation, whilst statistical filter is well-suited for vegetation cover consisting of tall trees. Conclusion The present study proposed and investigated different scenarios for the production offorest areas’ DTM using LiDAR data and two interpolation methods. These algorithms were practicallyassessed using LiDAR data collected from Dorood forest areas. The best scenario was slope-based filter with inverse distance weighting (IDW) interpolation. Based on accurate assessment, this approach can produce reliable DTM in forest areas.
Mehdi KhoshboreshMasouleh; Saeed Sadeghian
Abstract
Extended abstract
Introduction
Over the past two centuries, in many countries in the world, population density has dramatically grown in urban areas, resulting in cities to witness rising construction of multi-story apartment buildings and utilizing above and below ground spaces. Expansion of tower ...
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Extended abstract
Introduction
Over the past two centuries, in many countries in the world, population density has dramatically grown in urban areas, resulting in cities to witness rising construction of multi-story apartment buildings and utilizing above and below ground spaces. Expansion of tower construction and development of infrastructure networks are among the obvious examples of using above and below ground spaces of cities. Today, in order to manage these complex structures, the urban managers use three-dimensional urban models to plan for the future of the city. The land information is considered as the basis for the development of each country; among other things, cadaster as a parcel-based land information system can accurately determine the status and location of the real estates. Unlike the traditional cadastral system, the 3D cadaster is capable of modeling such features as buildings considering the third dimension i.e. height, thereby establishing the access rights for owners, whether individuals or organizations. Currently, the real estate management model is one of the best and most efficient ones for the implementation of 3D cadaster, which is originally developed based on the unified modeling language (UML). Accordingly, the aim of the present research is to generate a 3D urban cadastral model using the aerial imagery to improve the real estate management in the metropolitan area of Tehran by taking an executive approach.
Materials and Methods
This is an applied research, therefore, in order to ensure that the results are close to the reality and to consider the current conditions of Tehran in terms of the information required, the instructions for the provision of spatial information of the municipality of Tehran are used in the scale of 1:1000 by the photogrammetry method and the coordinated instructions of the national mapping organization are used for the production of a 3D cadastral model. The study was conducted in the northwest of Tehran in zone 5, district 5 of Tehran municipality. Being located in the foothills with the favorable climate, convenient access and distinctive urban fabric has caused the region to have the highest growth in the population and physical body for the last two decades. Besides, the passage of the metro line 2 (the busiest metro line of Tehran) and the line 10 of BRT buses (including long bus lines) in zone 5 in the area of the second square of Sadeghieh and the heavy population density in this region are among the most important criteria for choosing this area for the implementation of research objectives. The data used in this research are divided into two categories: spatial (geometric or situational) and descriptive data. Spatial data include aerial photogrammetric images (image pair) with 1:3000 scale using WILD-17126 cameras with the focal length of 303.40 mm and 0.5m contour interval under the UTM system, WGS84 reference ellipsoid and Ultracam XP digital camera images with the scale of 1:10,000.
Results and Discussion
Considering that the 1:1000 map of Tehran was prepared during 2010-2014 by the municipality of Tehran and used as a detailed map in Tehran city, the planimetric criteria and the matching of descriptive information and the criteria of height accuracy, field activity and production of accurate height data sets are done by land surveying of desired models. In order to evaluate the geometric accuracy of the model, the root mean square error (RMSE) and correlation coefficient (CC) were used. The results of the implementation on a total of three studied buildings show that the planimetric accuracy of the X and Y components were 1.451 m and 1.431 m for RMSE and 93.7% and 97.1% for CC, respectively. The accuracy of the height component with 2.605 m for RMSE and 66.5% for CC is consistent with the reference data. In addition, for analyzing the proposed research method, the model was compared with the object-oriented analysis, artificial neural network, manual digitization, and Khoshboresh&Sadeghian (2016) method, which was rated as appropriate, so that in only one case of planimetric accuracy and one case of height accuracy, the manual digitization method has better results than the proposed method.
Conclusion
Hence, it can be concluded that, although a 3D cadastral system has not been widely implemented in any country of the world, however, most countries seek to achieve such system by providing appropriate solutions, because as mentioned above, having such cadastral system, many problems related to land management and related crises can be solved. In this paper, the first prototype of 3D cadastral implementation in zone 5, district 5 of Tehran was analyzed using the large-scale digital aerial images. The results of this modeling show that the generated model matches the accuracy criteriaproperly.
Saeed Sadeghian
Volume 13, Issue 49 , May 2004, , Pages 31-35
Abstract
The history of the city of Karbala in Islamic Era begins since the martyrdom of Imam Hussein. Image (1) shows the space image of IKONOS, taken on January 3, 2003, from the shrine of Imam Hussein, along with the shrine of Abolfazl al Abbas and the spaces surrounding these two sites that form the central ...
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The history of the city of Karbala in Islamic Era begins since the martyrdom of Imam Hussein. Image (1) shows the space image of IKONOS, taken on January 3, 2003, from the shrine of Imam Hussein, along with the shrine of Abolfazl al Abbas and the spaces surrounding these two sites that form the central core of the city.
Saeed Sadeghian
Volume 7, Issue 27 , November 1998, , Pages 34-40
Abstract
The point of connection between aerial photos and data of satellite digital sensors is the high-resolution satellite photography using KFA-1000 cameras. In this paper, characteristics of KFA-1000 camera and satellite images, their systematic errors and the way of removing them, their methods of internal ...
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The point of connection between aerial photos and data of satellite digital sensors is the high-resolution satellite photography using KFA-1000 cameras. In this paper, characteristics of KFA-1000 camera and satellite images, their systematic errors and the way of removing them, their methods of internal justification, geometric correction, assessment of geometric precision and applications are examined.
Saeed Sadeghian
Volume 6, Issue 23 , November 1997, , Pages 54-61
Abstract
Tabari, in his important history book, refers to preparation of cadaster for whole lands of Iran during the reign of Kavad. It was so despite the fact that in those days Iran was a number of times vaster than its current area. Estakhri, living in tenth century A.D., has in his book, Sovar-al-Aghalim, ...
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Tabari, in his important history book, refers to preparation of cadaster for whole lands of Iran during the reign of Kavad. It was so despite the fact that in those days Iran was a number of times vaster than its current area. Estakhri, living in tenth century A.D., has in his book, Sovar-al-Aghalim, described lands, climates of earth, cities, seas, rivers and the distance between them in detail, and has displayed them on maps. These maps which amount to 19, are called Sovar. Taghvim-al-Boldan, written by Abolfada’, is one of the books written during the Middle Ages and a reference book in those times, and it has been translated since mid-sixteenth century into a number of European languages. a chapter of this book is about research on “area” and other chapter is about the areas of seven climates composed in line with the attitude of older times. Abolfada’ criticizes a number of former students because they hadn’t mentioned any data concerning the length and width of cities. Unfortunately, such activities did not continue in later times in an organize manner. Therefore, we must make double efforts to remove the shortages created by inaction.
Saeed Sadeghian
Volume 6, Issue 22 , August 1997, , Pages 52-61
Abstract
Data related to features of the earth’s surface have applications in many activities concerning planning, control and management of ground resources and man-made features. Data of this type are usually displayed on maps that show information on a reference plane. It is highly necessary that data ...
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Data related to features of the earth’s surface have applications in many activities concerning planning, control and management of ground resources and man-made features. Data of this type are usually displayed on maps that show information on a reference plane. It is highly necessary that data be ground-based, because it makes matching and combination of different sets of data possible.
A satellite image or photo provides an excellent outlook of a broad area of earth, thus presenting a comprehensive view of important physical and cultural features. Such images can be the best available data about many inaccessible areas of earth for which there are yet no reliable maps. However, a crude satellite image has defects such as distortion due to change of altitude, position of sensors, differences of altitude, earth’s spherical shape and lack of display of all features important for users. Consequently, in order to make best use of satellite images, data must be processed to remove distortions, extract three-dimensional information and practice interpretation of images for determination of type and use of features. Information obtained from other sources make completion of maps possible. Furthermore, by creating a network for displaying information system of national coordinates, the necessary consistency between the produced maps and other digital maps and data such as those available in a geographic information system can be realized.
