Landslides represent hazardous phenomena, often with significant implications. Monitoring landslides with time‐series surface observations can indicate surface failure. Unmanned aerial vehicles (UAVs) employing compact digital cameras, in conjunction with structure‐from‐motion (SfM) and multi‐view stereo (MVS) image processing approaches, have become commonplace in the geoscience research community. These methods offer relatively low‐cost, flexible solutions for many geomorphological monitoring applications. However, conventionally ground control points (GCPs) are required for registration purposes, the provision of which is often expensive, difficult or even impracticable in hazardous and inaccessible terrain.

Unmanned aerial vehicles (UAVs) can provide observations of high spatio-temporal resolution to enable operational landslide monitoring. In this research, the construction of digital elevation models (DEMs) and orthomosaics from UAV imagery is achieved using structure-from-motion (SfM) photogrammetric procedures. The study examines the additional value that the morphological attribute of "openness", amongst others, can provide to surface deformation analysis. Image-cross-correlation functions and DEM subtraction techniques are applied to the SfM outputs. Through the proposed integrated analysis, the automated quantification of a landslide's motion over time is demonstrated, with implications for the wider interpretation of landslide kinematics via UAV surveys.

A methodology is developed to estimate daily river discharge at an ungauged site using remote sensing data. Use is made of ERS-2 and ENVISAT satellite altimetry to provide a time series of river channel stage levels and longitudinal channel slope and Landsat satellite imagery to provide a range of channel widths over a 50km reach of river. The data are substituted into the Bjerklie et al. () equation, which is based on the Manning's resistance equation and has been developed using a global database of channel hydraulic information and discharge measurements. Our methodology has been applied at three locations on the Mekong and Ob Rivers and validated against daily in situ discharge measurements. The results show Nash-Sutcliffe efficiency values of 0.90 at Nakhon Phanom and 0.86 at Vientiane on the Mekong, and 0.86 at Kalpashevo on the Ob. Copyright (c) 2012 John Wiley & Sons, Ltd.

Satellite altimetry is routinely used to provide levels for oceans or large inland water bodies from space. By utilizing retracking schemes specially designed for inland waters, meaningful river stages can also be recovered when standard techniques fail. Utilizing retracked waveforms from ERS‐2 and ENVISAT along the Mekong, comparisons against observed stage measurements show that the altimetric measurements have a root mean square error (RMSE) of 0·44–0·65 m for ENVISAT and 0·46–0·76 m for ERS‐2. For many applications, however, stage is insufficient because discharge is the primary requirement. Investigations were therefore undertaken to estimate discharges at a downstream site (Nakhon Phanom (NP)) assuming that in situ data are available at a site 400 km upstream (Vientiane). Two hypothetical, but realistic scenarios were considered. Firstly, that NP was the site of a de‐commissioned gauge and secondly, that the site has never been gauged. Using both scenarios, predictions were made for the daily discharge using methods with and without altimetric stage data. In the first scenario using a linear regression approach the altimetry data improved the Nash‐Sutcliffe r 2 value from 0·884 to 0·935. The second scenario used known river cross‐sections while lateral inflows were inferred from a hydrological model: this scenario gave an increase in the r 2 value from 0·823 to 0·893. The use of altimetric stage data is shown to improve estimated discharges and further applications are discussed. Copyright © 2010 John Wiley & Sons, Ltd.

Satellite altimetry provides a precise measure of the vertical distance of the satellite borne altimeter to the instantaneous sea surface. The accuracy of this distance depends on the calibration of the altimeter, the quality of the reflecting target and the proper estimate of path delay. The general design characteristics for absolute altimeter calibration imply a large number of measurements to reduce the random errors, diversity of measurement techniques and independent data analysis, to reduce the susceptibility to systematic errors. Part of the altimeter calibration can be undertaken by comparison against in situ tide gauge data and GPS buoys, by inter-comparison between two altimeter data sets from concurrent satellites, or at crossing points. A different, convenient and independent technique is the use of a dedicated transponder, a device that receives the signal from the altimeter, amplifies it and re-sends it back to the satellite. Opposite to the ocean surface, a transponder disposes of a stable and very precise reflection reference (few millimeters), which allows for a very precise determination of the vertical distance between the satellite and the transponder. The accuracy of such a determined range depends on the ability to estimate the path delays caused by the atmosphere, the precision of the orbit and the GPS positioning of the transponder. Using precise orbits recalculated for each individual pass, the altimeter bias has been determined using Envisat waveforms produced by the transponder between 2004-2005.

This paper describes how the phase sequence and voltage level (132 kV, 275 kV or 400 kV) of single-circuit overhead conductors can be calculated from measurements made by passive, non-contact sensors situated on a moving platform at ground level.The investigation relies on sensing the electric field along the profile of the conductors through the use of passive sensors. The fabrication of the passive sensor is described together with an analysis of its performance. The variation of the vertical component of electric field strength along the lateral profile beneath single-circuit conductors has been studied using finite element modeling software, ANSYS. The results of this simulation have led to a proposed method of determining the magnitude and phase sequence information from overhead conductors via analysis of the induced voltages on the sensors.The paper concludes with an investigation made in a 400 kV substation in the UK. Analysis of the experimental results shows that the proposed technique can successfully evaluate the phase sequence, voltage level, the spacing between phases and the orientation of high-voltage overhead conductors.