The Autonomous Mini Helicopter: A powerful Platform for Mobile Mapping

In this paper, the developments related to an autonomous airborne mobile mapping system for photogrammetric processing will be presented. During the last years the author has been involved in several projects related to mobile mapping using an autonomously flying model helicopter, a so-called mini UAV (Unmanned Aerial Vehicle). The overall motivation of using mini UAVs for mobile mapping, the developed workflow for UAV-data processing, the current status of the work, and recent developments related to specific applications are described. In a first step our mini UAV-system and our approach are explained and the need for specific developments is highlighted. In the following two applications will be described: The Randa rockslide and the maize project, demonstrating our developments for the automation of the photogrammetric workflow using the mini UAV system. In the Randa project a unique flight planning tool for UAV-monitoring of mountainous areas was developed. The tool allows for the adaptation of the flight in a way, that image data with 2-3 cm resolution of the cliff could be acquired. Moreover, due to this high image resolution, a DSM with a higher point density compared to standard airborne and helicopter-based LIDAR-systems, could be generated. In the second project the focus was on the automation of the image orientation process. Hence, two test areas (A and B) were defined. While in A two commercial photogrammetric workstation were evaluated, in B the data set was processed using GPS/INS data as initial values for the image orientation. Therefore, the manual input for the aerial triangulation was reduced to a minimum user interaction. Finally, with the oriented image data two DSMs for the analysis of the outcrossing in maize were generated. Because of these developments, the tools for the planning and the data acquisition as well as the workflow for the processing of UAV-image

UAVs For The Documentation Of Archaeological Excavations

UAV photogrammetry experienced a growing variety of diverse applications in different scientific disciplines. Comparable early, UAVs were deployed in the Cultural Heritage and Archaeology domains, mainly for the purpose of monument, building and landscape modelling. In this paper, we will focus on the investigation of UAV application for documenting archaeological excavations. Due to the fact, that excavations are dynamic processes and therefore the objects to be acquired change significantly within few hours, UAVs can provide a suitable alternative to traditional measurement methods such as measuring tape and tachymeter in some cases. Nevertheless, the image processing steps have to be automated to a large amount as results, usuallysketches, maps, orthophotos and 3D models, should be available temporallyclose to the related excavation event. In order to accelerate the processing workflow, an interface between the UAV ground control software and various photogrammetric softwarepackages was developed at ETH Zurich which allows for an efficient management and transfer of orientation, trajectory and sensor data for fast project setup. The capabilities of photogrammetric methods using UAVs as a sensor platform will be demonstrated in 3case studies: The documentation of a large archaeological site in Bhutan,an excavation of a smaller site containing ancient tombs which include several uncovered objects in the Nasca region in Peruand the Maya site of Copán in Honduras.The first and the third case study deal with the 3D modelling of buildings and their remains by means of photogrammetry, which means that accurate flight planning had to be applied and followed during the flights.In the second case study, we acquired various aerial images over the excavation area Pernil Alto near Palpain a more simple way forquick documentation of the area of interest. In a third part, we will present our results from comparisons between the planned positions for image acquisition and the positions realized by the navigation unit during the flight for both UAV systems mentioned above. We will describe how accurate orientation data improve automated image processing if they are at hand directly after the flight and explain the workflow developed at ETH Zurich.ISSN:1682-1750ISSN:2194-9034ISSN:1682-177

Comparison of DSMs generated from mini UAV imagery and terrestrial laser scanner in a cultural heritage application

In this paper we present two different methods, which were applied for the DSM generation of the cultural heritage site Pinchango Alto. The area of interest is a LIP (Late Intermediate Period; 1400 AD) settlement, situated 400 km in the south of the capital of Peru (Lima) close by the famous Geoglyphs of Nasca. The site was recorded using a terrestrial laser scanner (Riegl LMS-Z420i) and a mini UAV-system (Unmanned Aerial Vehicle) under the framework of a research program called NTG (“New methods and technologies in the humanities”). During the field work, using both methods, the complete settlement was documented in a short time. The post-processing of the data was done by use of in-house developed software packages. The image data (UAV) were oriented and a DSM (10 cm resolution) was generated automatically using a multi-image matching approach. For the registration of the single laser scans a surface matcher rather than the special targets was used. As a product of the laser data a regular raster grid with point spacing of 5 cm was generated. The 3D comparison of both elevation models shows a mean value less than 1 cm with a standard deviation of 6 cm. The main discrepancy between the data sets results mostly from occlusion, caused on the restricted viewing directions of the acquisition stand points. The presented data acquisition and processing methods showed their high usability for the documentation of archaeological sites.ISSN:1682-1750ISSN:2194-9034ISSN:1682-177

Accurate DSM production from unmanned helicopter systems

Since the previous ISPRS conference in 2004 there have been several developments in modern navigation and earth observation. One of the new developments is accurate production of dense Digital Surface Models (DSMs), three-dimensional (3D) vector maps, and high resolution orthophotos from unmanned aerial vehicles (UAVs) with a state-of-the-art navigation and control system for hands-off autonomous flights. The authors have successfully completed several scientific and commercial photogrammetric projects using these UAVs for a variety of applications, like for example modelling archeological sites on the Unesco world heritage list, creating high quality and realistic three-dimensional building models for urban planning, producing three-dimensional cadastral and transportation map updates, reconstructing mountain rock faces, and calculating volumes of stock piles. This paper presents theresults of four particular show case projects: a highway and the Geofort in the Netherlands and two projects in Switzerland: a corn field and the Rand rockslide. The UAV photogrammetric products have been validated with geodetic terrestrial survey data. Typical products are 2-cm seamless orthophotos, three-dimensional vector maps and dense DSMs of approximately 50 points per m2 with a relative point precision of better than 2 cm in XY and 4 cm in height. The paper finally presents the results of the produced DSMs of the projects with high resolution and accuracy.ISSN:1682-1750ISSN:2194-9034ISSN:1682-177