CALIBRATION STUDY OF A TRIMBLE ACx4 SYSTEM FOR DIRECT GEOREFERENCING MAPPING APPLICATIONS

The Trimble Aerial Camera x4 (i.e., TACx4) is a photogrammetric multi-head system manufactured by Trimble Inc.© in 2010. It has four cameras mounted together in the main structure allowing the simultaneous acquisition to generate a single synthetic image with much larger ground coverage. In addition, the cameras are also integrated with a GNSS/INS to perform “Direct” or “Integrated” Sensor Orientation. The main condition to obtain photogrammetric mapping products with high accuracy using a direct sensor orientation procedure is to execute a step known as “geometric system calibration”. In general, the photogrammetric multi-head system manufacturers perform this step using laboratory methods to obtain the parameters of cameras interior and relative orientation. Accurate mounting parameters (lever arms and “boresight misalignments”) are fundamental requirements to generate the synthetic image when georeferencing of images is applied. This paper shows a “full field” calibration method to perform the geometric system calibration of the TACx4 system and its evaluation for direct sensor orientation mapping applications. The developed method involves two steps using only aerial images: (1) estimation of the cameras interior and relative orientation parameters to generate the synthetic image and (2) estimation of the synthetic image interior orientation and the mounting parameters between the synthetic image and GNSS/INS reference systems using two different methods. The obtained results in the conventional photogrammetric project show that the proposed method allows performing the geometric system calibration of the TACx4 system achieving around 50 cm (5 pixels) in horizontal and vertical accuracies. The obtained results can be used for large-scale mapping requirements using direct sensor orientation according to Brazilian accuracy standards

USE OF UAV PLATFORM AS AN AUTONOMOUS TOOL FOR ESTIMATING EXPANSION ON INVADED AGRICULTURAL LAND

For a long time, in many countries, questions involving disputes about land ownership has generated demand for geoinformation and documentation. In most cases, access for researchers is restricted or humanely impossible by eminence of conflicts, even armed. In these cases, researchers use Remote Sensing and Photogrammetry to enable their studies. However, the dynamics of the phenomenon being studied often requires approaches that traditional techniques become unviable or unable to fulfil. This work shows the results of an approach that used a photogrammetric UAV platform to take pictures of an invaded rural area in Brazil and estimate its expansion over two years. From the taken images, mosaics were generated and then classified using Decision Tree to identify tents. Then it was developed a Matlab algorithm, to detect and quantify the tents on the classified Images. It was possible to infer that there was an expansion of 7.3% between the two analyzed dates and probably more than three thousand people occupied the invasion site

Mitishita Integration of Laser and Photogrammetric Data for Calibration Purposes .ISPRS conference

Laser scanners are becoming popular since they provide fast and dense geometric surface information. However, sudden elevation changes along the surface are not clearly visible in the laser data due to the sparse distribution of captured points. In general, laser data provides high density surface information in homogenous areas and low density surface information elsewhere (i.e., object space break-lines). Photogrammetry, on the other hand, provides less dense surface information but with high quality, especially along object space discontinuities. Hence, a natural synergy of both systems can be inferred and consequently integration of the respective data would lead to higher quality surface information than that obtained through the use of a single sensor. However, prior to such integration, both systems should be precisely calibrated and aligned. The calibration is usually carried-out for each system independently using additional control information. In this paper, the calibration of the laser and photogrammetric systems is evaluated by checking the quality of fit between co-registered photogrammetric and laser surfaces. The paper starts by introducing a registration procedure where a set of linear features is extracted from both sets. First, planar surfaces from laser data are extracted and adjacent planes are intersected to determine three-dimensional straight line segments. Secondly, linear features from the photogrammetric dataset are obtained through aerial triangulation. A mathematical model for expressing the necessary constraints for the alignment of conjugate photogrammetric and laser straight lines is established. The model ensures that corresponding straight lines will be collinear after registering the two datasets relative to a common reference frame. The quality of fit between th

USE OF UAV PLATFORM AS AN AUTONOMOUS TOOL FOR ESTIMATING EXPANSION ON INVADED AGRICULTURAL LAND

Abstract: For a long time, in many countries, questions involving disputes about land ownership has generated demand for geoinformation and documentation. In most cases, access for researchers is restricted or humanely impossible by eminence of conflicts, even armed. In these cases, researchers use Remote Sensing and Photogrammetry to enable their studies. However, the dynamics of the phenomenon being studied often requires approaches that traditional techniques become unviable or unable to fulfil. This work shows the results of an approach that used a photogrammetric UAV platform to take pictures of an invaded rural area in Brazil and estimate its expansion over two years. From the taken images, mosaics were generated and then classified using Decision Tree to identify tents. Then it was developed a Matlab algorithm, to detect and quantify the tents on the classified Images. It was possible to infer that there was an expansion of 7.3% between the two analyzed dates and probably more than three thousand people occupied the invasion site