Ground waves and sky waves measured 209 km and 250 km south of six triggered lightning flashes containing 30 strokes that occurred in the half-hour before sunset on 27 August 2015 are presented and analyzed. We use a cross-correlation technique to find the ionospheric effective reflection height and compare our results to previous techniques that calculate effective height based on the time del...

Current approaches to local rough-terrain navigation are limited by their ability to build a terrain model from sensor data. Available sensors make very indirect measurements of quantities of interest such as the supporting ground surface and the location of obstacles. This is especially true in domains where vegetation may hide the ground surface or partially obscure obstacles. This thesis pre...

Observations of tsunamis away from shore are critically important for improving early warning systems and understanding of tsunami generation and propagation. Tsunamis are difficult to detect and measure in the open ocean because the wave amplitude there is much smaller than it is close to shore. Currently, tsunami observations in deep water rely on measurements of variations in the sea surface...

The observed reduction in cloud-to-ground lightning in the near-equatorial zone is examined from the perspective of the width of the main negative charge region. Thermodynamic observations of cloud base height also show a minimum value in the near-equatorial region. The association of low cloud bases with both narrow updrafts and narrow charging zones may impede the bridging of the large air ga...

Crop improvement efforts are targeting increased above-ground biomass and radiation-use efficiency as drivers for greater yield. Early ground cover and canopy height contribute to biomass production, but manual measurements of these traits, and in particular above-ground biomass, are slow and labor-intensive, more so when made at multiple developmental stages. These constraints limit the abilit...

Randommeasurement errors in digital terrain models are important to their quality. The present paper describes an untypical use of variograms to compute this kind of measurement errors. After subtracting a low frequency drift from depth/height measurements, a variogram analysis of the residuals is used to derive the random measurement errors of the observations. Numerical experiments on laserca...

Tropical montane forests provide an important natural laboratory to test ecological theory. While it is well-known that some aspects of forest structure change with altitude, little is known on the effects of altitude on above ground biomass (AGB), particularly with regard to changing height-diameter allometry. To address this we investigate (1) the effects of altitude on height-diameter allome...

Two methods are considered for the improvement of the ephemerides of the asteroids observed by the Hipparcos satellite. They utilize different combinations of ground-based and space-based data. In particular, we develop a method based on an analysis of the variance matrix in the least-squares solution of Hipparcos observations taken alone. Application and comparison of the results for (2) Palla...

Forest height is of great significance in analyzing the carbon cycle on a global or a local scale and in reconstructing the accurate forest underlying terrain. Major algorithms for estimating forest height, such as the three-stage inversion process, are depending on the random-volume-over-ground (RVoG) model. However, the RVoG model is characterized by a lot of parameters, which influence its a...

Nowadays GPS is widely used to monitor the ionosphere. However, the current results from ground-based GPS observations only provide some information on the horizontal structure of the ionosphere, and are extremely restricted in mapping its vertical structure. In this paper, tomography reconstruction technique was used to image 3D ionospheric structure with ground-based GPS. The first result of ...