Comparison of a Fixed-Wing and Multi-Rotor Uav for Environmental Mapping Applications: A Case Study

Abstract

Commission VI, WG VI/4KEY WORDS: UAV, fixed-wing, multi-rotor, photogrammetry, environmental mapping, orthoimage, DSM ABSTRACT:The advent and evolution of Unmanned Aerial Vehicles (UAVs) and photogrammetric techniques has provided the possibility for on-demand high-resolution environmental mapping. Orthoimages and three dimensional products such as Digital Surface Models (DSMs) are derived from the UAV imagery which is amongst the most important spatial information tools for environmental planning. The two main types of UAVs in the commercial market are fixed-wing and multi-rotor. Both have their advantages and disadvantages including their suitability for certain applications. Fixed-wing UAVs normally have longer flight endurance capabilities while multi-rotors can provide for stable image capturing and easy vertical take-off and landing. Therefore, the objective of this study is to assess the performance of a fixed-wing versus a multi-rotor UAV for environmental mapping applications by conducting a specific case study.The aerial mapping of the Cors-Air model aircraft field which includes a wetland ecosystem was undertaken on the same day with a Skywalker fixed-wing UAV and a Raven X8 multi-rotor UAV equipped with similar sensor specifications (digital RGB camera) under the same weather conditions. We compared the derived datasets by applying the DTMs for basic environmental mapping purposes such as slope and contour mapping including utilising the orthoimages for identification of anthropogenic disturbances. The ground spatial resolution obtained was slightly higher for the multi-rotor probably due to a slower flight speed and more images. The results in terms of the overall precision of the data was noticeably less accurate for the fixed-wing. In contrast, orthoimages derived from the two systems showed small variations. The multi-rotor imagery provided better representation of vegetation although the fixed-wing data was sufficient for the identification of environmental factors such as anthropogenic disturbances. Differences were observed utilising the respective DTMs for the mapping of the wetland slope and contour mapping including the representation of hydrological features within the wetland. Factors such as cost, maintenance and flight time is in favour of the Skywalker fixedwing. The multi-rotor on the other hand is more favourable in terms of data accuracy including for precision environmental planning purposes although the quality of the data of the fixed-wing is satisfactory for most environmental mapping applications.

Application of UAV Imagery to Detect and Quantify Submerged Filamentous Algae and Rooted Macrophytes in a Non-Wadeable River

“…When target algal or macrophyte patches are identifiable at large spatial scales, or when higher spectral resolution is required to discern among taxa, high-resolution satellite imagery can be an alternative to UAV imagery [109]. Fixed-wing UAVs may be difficult to fly in meandering river environments unless there are open riverbanks or roads adjacent to the study sites that can be used for take-off and landing [110]. As river survey extent increases, UAV data increases, thereby posing additional constraints to computational processing time.…”

Contribuciones metodológicas para la obtención de información altimétrica requerida en la evaluación local de amenazas por inundaciones a partir de nuevas tecnologías geoespaciales

“…Esto define la mínima unidad cartografiable en el terreno o el tamaño del píxel de la imagen Ground Sample Distance (GSD). Para un cubrimiento mayor de área se recurre a plataformas tipo ala fija, mientras plataformas multirotor son usualmente empleadas para pequeñas superficies (Boon, Drijfhout, & Tesfamichael, 2017). Si se demanda una elevada precisión deberemos ir a plataformas multirotor, ya que las de tipo ala fija al tener que operar a velocidades o alturas más altas, las precisiones son menores si se compara con los productos altimétricos derivados de un multirotor .…”

“…En el caso de no contar con suficiente energía suministrada por la batería de la plataforma para cubrir toda la superficie de interés, es necesario ejecutar la misión en varios vuelos. Una limitante importante de los RPAS es el tiempo de vuelo de la aeronave, principalmente condicionado por factores internos como la capacidad de los baterías y externos como la velocidad del viento (Boon et al, 2017;Manfreda et al, 2018). Las misiones para modelos detallados y precisos requieren generalmente de altos solapamientos y vuelos de baja altitud, por lo general con un número alto de vuelos, requiriendo el uso extra de baterías.…”

“…i) Tipo de plataforma: Como se observa en la figura 5 son dos los tipos de plataforma RPAS: las plataformas tipo multirotor y las plataformas tipo ala fija. Las plataformas tipo multirotor (figura 5a) son los más utilizados para crear mapas y modelos en aplicaciones fotogramétricas cuando es requerido un alto nivel de detalle (Boon et al, 2017;Colomina & Molina, 2014;Olson & Rouse, 2016). Se componen de un cuerpo central y de múltiples rotores con hélices permitiendo la sustentación y control.…”

“…Una vez en el aire, las hélices controlan el movimiento de la aeronave variando la velocidad relativa de cada rotor. Las plataformas tipo ala fija (figura 5b) están diseñadas como las aeronaves tripuladas convencionales (Beard et al, 2005;Boon et al, 2017). La aeronave consiste en una superficie de ala rígida de perfil determinado haciendo posible el vuelo al generar sustentación debido a la velocidad de desplazamiento.…”