Dimitris Kaimaris

UAV and the comparison of image processing software

Purpose The purpose of this paper is to discuss unmanned aerial vehicle (UAV) and the comparison of image processing software. Design/methodology/approach Images from a drone are used and processed with new digital image processing software, Imagine UAV® of Erdas imagine 2015®. The products (Digital Surface Model and ortho images) are validated with check points (CPs) measured in the field with Global Positioning System. Moreover, similar products are produced by Agisoft PhotoScan® software and are compared with both the products of Imagine UAV and the CPs. Findings The results reveal that the two software tools are almost equivalent, while the accuracies of their products are similar to the accuracies of the external orientations of drone images. Originality/value Comparison of image processing software.

Evaluating horizontal positional accuracy of low-cost UAV orthomosaics over forest terrain using ground control points extracted from different sources

Within the field of forestry, forest road mapping and inventory plays an important role in management activities related to wood harvesting industry, sentiment and water run-off modelling, biodiversity distribution and ecological connectivity, recreation activities, future planning of forest road networks and wildfire protection and fire-fighting. Especially in countries of the Mediterranean Rim, knowledge at regional and national scales regarding the distribution and the characteristics of rural and forest road network is essential in order to ensure an effective emergency management and rapid response of the fire-fighting mechanism. Yet, the absence of accurate and updated geodatabases and the drawbacks related to the use of traditional cartographic methods arising from the forest environment settings, and the cost and efforts needed, as thousands of meters need to be surveyed per site, trigger the need for new data sources and innovative mapping approaches. Monitoring the condition of unpaved forest roads with unmanned aerial vehicle technology is an attractive option for substituting objective, laboursome surveys. Although photogrammetric processing of UAV imagery can achieve accuracy of 1-2 centimeters and dense point clouds, the process is commonly based on the establishment of control points. In the case of forest road networks, which are linear features, there is a need for a great number of control points. Our aim is to evaluate low-cost UAV orthoimages generated over forest areas with GCP’s captured from existing national scale aerial orthoimagery, satellite imagery available through a web mapping service (WMS), field surveys using Mobile Mapping System and GNSS receiver. We also explored the direct georeferencing potential through the GNSS onboard the low cost UAV. The results suggest that the GNSS approach proved to most accurate, while the positional accuracy derived using the WMS and the aerial orthoimagery datasets deemed satisfactory for the specific task at hand. The direct georeferencing procedure seems to be insufficient unless an onboard GNSS with improved specifications or Real-Time Kinematic (RTK) capabilities is used.

Assessment and mapping of urban environmental quality using remote sensing and geospatial data

Urban environmental management is of profound importance due to increasing urban development alongside the need to develop resilient cities and sustainable urbanization strategies. Spatial explicit urban environmental quality indices can provide policy makers and the public with valuable information for urban planning and policy formation. The aim of this study is the development of a multi-component urban environmental quality index for the metropolitan area of Thessaloniki. The approach was designed to be robust and easily transferred across cities with similar characteristics. Land Surface Temperature (LST) was estimated based on multi-seasonal Landsat-8 images, while Fractional Vegetation Cover (FVC) was derived from fused Sentinel-2 images and validated using WorldView-2 very high spatial resolution imagery. In addition, several geospatial layers related to atmospheric pollution, petroleum refineries, noise pollution, urban density and distance to green infrastructures were processed within GIS environment and integrated with the satellite extracted information. A multi-criteria Analytical Hierarchical Approach (AHP) was used for integrating the sub-criteria to a final urban environmental quality index using weights from expert knowledge and literature review. The results identified extended areas in the western part of the study region as well as several hot spots in the eastern part, that local planners should develop and implement actions for improving living conditions of residents. Overall, the method proved to be viable and flexible and its application can be expanded to similar Mediterranean cities.

Unmanned Aerial Vehicles and the Multi Temporal Mapping Results of the Dispilio Lakeside Prehistoric Settlement

In this paper the authors present the evolution of the Unmanned Aerial Vehicles (UAV) and photogrammetric processing software technology through the multi temporal mapping of the lakeside Palaeolithic settlement of Dispilio (Kastoria, Greece). The study of the settlement initiated in 2006 using a Remote Control (RC) Helicopter, which was not equipped with an automated navigation and image acquisition system. Currently a multi-copter drone is used that can demonstrate flight stability, is capable of hovering in small heights and is equipped with an automated navigation and image acquisition system. With respect to the photogrammetric processing software at the start of the study specialized single image processing software like Bentley IRAS/c® were used for the production of rectified images, followed by the use of stereo image processing software like LPS® (Erdas) that have the ability to produce B/W Digital Terrain Models (DTM) and ortho rectified images. Currently specialized multi photo processing software is used like Agisoft Photoscan® or Imagine UAV® (Erdas) that the ability to produce dense coloured point clouds and ortho rectified images.

Aerial and Remote Sensing Archaeology

New techniques and methodological procedures, which would allow at a short time and at low cost for the identification of a new archaeological sites, were always in the interest of archaeologists. In addition, fast and accurate 3D modelling and documentation techniques were also always a hot research topic because they can help archeologists to document active excavation sites fast, thus helping them to advance the excavation in a timely manner. In this chapter, aerial and remote sensing archaeology issues will be analyzed, both as measuring tools for the documentation of existing archaeological structures as well as tools of archaeology prospection, which are based on the appearance of the reflection of covered structures in images (i.e., the so-called marks).