Table 1 Input data of the integrated model and necessary assumptions of UAV-based and field-based data collection

From: Integration of photogrammetry from unmanned aerial vehicles, field measurements and discrete fracture network modeling to understand groundwater flow in remote settings: test and comparison with geochemical markers in an Alpine catchmentIntégration de la photogrammétrie à partir de drones, de mesures sur le terrain et de la modélisation de réseaux de fractures discrètes pour comprendre l’écoulement des eaux souterraines dans des endroits éloignés: test et comparaison avec des marqueurs géochimiques dans un bassin versant alpinIntegración de la fotogrametría de drones, mediciones sobre el terreno y modelización de redes de fracturas discretas para comprender el flujo de aguas subterráneas en escenarios remotos: prueba y comparación con trazadores geoquímicos en una cuenca alpina集成了无人机的摄影测量,实测和离散裂缝网络建模,以了解偏远地区的地下水流:在高山流域与地球化学标记物进行测试和比较Integração da fotogrametria de veículos aéreos não tripulados, medições de campo e modelagem discreta da rede de fraturas para entender o fluxo de águas subterrâneas em ambientes remotos: teste e comparação com marcadores geoquímicos em uma bacia de captação alpina

Parameter Data collection from the field and assumptions Data collection from UAV and assumptions Input for the integrated model
Fracture intensity Measured from selected transects on site and converted to P32 valuea (Priest and Hudson 1981) Measured from selected transects and converted to P32 value (Priest and Hudson 1981) From UAV model, when both measurements are present. When fracture data were not observed by UAV, they were obtained from field data
Fracture length Outcrop-scale fracture lengths were multiplied by 10, assuming 10% relative standard deviation Mean and standard deviation measured from virtual outcrops From UAV-based model, when available; alternatively, from ground-based data
Fracture-set orientation Field-survey data on mean orientation and Fisher’s K for dispersion Virtual-outcrop data on mean orientation and Fisher’s K for dispersion Recalculation of mean orientation and Fisher K value for the clusters containing both fractures observed in the field and by UAV
Aspect ratio (height/length) Not available Obtained from 2D shapes of reconstructed fractures From UAV model, when available; alternatively, assumed as 1:7 (the average value from UAV data)
Aperture From field survey Not available From field survey, when available; alternatively assumed with an increase proportional to root of length from virtual outcrop (Klimczak et al. 2010), with minimum value of 1 mm
  1. aP32 = volumetric fracture density, expressed as the area of fractures (m2) per unit of rock volume (m3)