The use of UAVs in engineering geological surveys: mapping along Scotland's south-west coast

UAVs have been used in engineering for at least two decades. While there is a wide range of recognition algorithms for the automatic identification of structural damage, structural geological features etc. from the acquired images, the parameters affecting the resolution of these images are often overlooked. As a result, the potential of the UAV technology is not maximized and at times, it is even regarded as leading to poor outcomes. We present a case study of the structural geological mapping of a coastal area in Scotland carried out using two types of UAVs: a fixed wing and a hexacopter. We compare the structural geological maps obtained from the orthophotos and conventional techniques and find that although the level of detail is the same, the time spent in producing a map is at least 5 times less when using a UAV. The fixed wing is faster and therefore, can cover large areas while the copter gives better resolution images as it can fly at lower heights. The level of detail achieved in this study was 1 cm which is sufficient for most mapping applications. The time required to produce a structural geological map of the studied area was a fifth of the time required when using conventional mapping techniques. The use of one or the other type of UAVs and the flight height depend on the needs of the project and should be chosen after taking into consideration the required resolution.