Urban land cover classification using airborne LiDAR data: A review

Beyond 3-D: The New Spectrum of Lidar Applications for Earth and Ecological Sciences

The past decade has seen an explosive increase in the number of peer reviewed papers reporting new scientific findings in geomorphology (including fans, channels, floodplains and landscape evolution), geologic mapping, tectonics and faulting, coastal processes, lava flows, hydrology (especially snow and runoff routing), glaciers and geo-archaeology. A common genesis of such findings is often newly available decimeter resolution 'bare Earth' geodetic images, derived from airborne laser swath mapping, a.k.a. airborne LiDAR, observations. In this paper we trace nearly a half century of advances in geodetic science made possible by space age technology, such as the invention of short-pulse-length high-pulse-rate lasers, solid state inertial measurement units, chip-based high speed electronics and the GPS satellite navigation system, that today make it possible to map hundreds of square kilometers of terrain in hours, even in areas covered with dense vegetation or shallow water. To illustrate the impact of the LiDAR observations we present examples of geodetic images that are not only stunning to the eye, but help researchers to develop quantitative models explaining how terrain evolved to its present form, and how it will likely change with time. Airborne LiDAR technology continues to develop quickly, promising ever more scientific discoveries in the years ahead.

https://iopscience.iop.org/article/10.1088/0034-4885/76/8/086801/pdf

Geodetic imaging with airborne LiDAR: the Earth's surface revealed

Review of Earth science research using terrestrial laser scanning

Airborne and spaceborne remote sensing for archaeological and cultural heritage applications: A review of the century (1907–2017)

The first demonstration of a multispectral light detection and ranging (LiDAR) optimized for detailed structure and physiology measurements in forest ecosystems is described. The basic principle is to utilize, in a single instrument, both the capacity of multispectral sensing to measure plant physiology [through normalized difference vegetation index (NDVI) and photochemical reflectance index (PRI)] with the ability of LiDAR to measure vertical structure information and generate “hot spot” (specular) reflectance data independent of solar illumination. A tunable laser operated at four wavelengths (531, 550, 660, and 780 nm) was used to measure profiles of the NDVI and the PRI. Laboratory-based measurements were conducted for live trees, demonstrating that realistic values of the indexes can be measured. A model-based analysis demonstrates that the LiDAR waveforms cannot only capture the tree height information but also picks up the seasonal and vertical variation of NDVI inside the tree canopy.

/pdf/a-multispectral-canopy-lidar-demonstrator-project-1adcf1l747.pdf

A Multispectral Canopy LiDAR Demonstrator Project

In the quest for a better understanding of climate change, greater importance is attached to monitoring the levels of atmospheric carbon dioxide to gain an improved knowledge of sources and sinks. Remote sensing is a critical tool in this research area and differential absorption lidar (DIAL) is one important technique. The laser is the critical component of a DIAL instrument. This paper describes the development of a laser source for the detection and measurement of carbon dioxide.

/pdf/development-of-a-laser-for-differential-absorption-lidar-2flxbnd1nl.pdf

Development of a laser for differential absorption lidar measurement of atmospheric carbon dioxide

Several lines of evidence suggest that glial cells have major effects on neuronal pathfinding. We have examined in vitro whether the outgrowth pattern of Xenopus retinal fibres is influenced by the glial cells encountered as they grow to the optic tectum. Strips of retina were cultured on monolayers of glial cells from the diencephalon and from the rostral and caudal ends of the optic tectum. On glia from the caudal end of the tectum the growth of fibres from the nasal and temporal ends of the strips was different: temporal fibres were shorter and more fasciculated than nasal fibres. This difference was still discernible on glia isolated from the rostral end of the tectum, but to a lesser extent. On glia from the diencephalon there was no difference between nasal and temporal fibres.

Retinal axons in Xenopus show different behaviour patterns on various glial substrates in vitro.

We report the development of a differential absorption lidar instrument (DIAL) designed and built specifically for the measurement of anthropogenic greenhouse gases in the atmosphere. The DIAL is integrated into a commercial astronomical telescope to provide high-quality receiver optics and enable automated scanning for three-dimensional lidar acquisition. The instrument is portable and can be set up within a few hours in the field. The laser source is a pulsed optical parametric oscillator (OPO) which outputs light at a wavelength tunable near 1.6 μm. This wavelength region, which is also used in telecommunications devices, provides access to absorption lines in both carbon dioxide at 1573 nm and methane at 1646 nm. To achieve the critical temperature stability required for a laserbased field instrument the four-mirror OPO cavity is machined from a single aluminium block. A piezoactuator adjusts the cavity length to achieve resonance and this is maintained over temperature changes through the use of a feedback loop. The laser output is continuously monitored with pyroelectric detectors and a custom-built wavemeter. The OPO is injection seeded by a temperature-stabilized distributed feedback laser diode (DFB-LD) with a wavelength locked to the absorption line centre (on-line) using a gas cell containing pure carbon dioxide. A second DFB-LD is tuned to a nearby wavelength (off-line) to provide the reference required for differential absorption measurements. A similar system has been designed and built to provide the injection seeding wavelengths for methane. The system integrates the DFB-LDs, drivers, locking electronics, gas cell and balanced photodetectors. The results of test measurements of carbon dioxide are presented and the development of the system is discussed, including the adaptation required for the measurement of methane.

/pdf/a-robust-optical-parametric-oscillator-and-receiver-3c3qzftvvn.pdf

A robust optical parametric oscillator and receiver telescope for differential absorption lidar of greenhouse gases

Understanding the dynamics of the global carbon cycle is one of the most challenging issues for the scientific
community. The ability to measure the magnitude of terrestrial carbon sinks as well as monitoring the short and long
term changes is vital for environmental decision making. Forests form a significant part of the terrestrial biosystem and
understanding the global carbon cycle, Above Ground Biomass (AGB) and Gross Primary Productivity (GPP) are critical
parameters. Current estimates of AGB and GPP are not adequate to support models of the global carbon cycle and more
accurate estimates would improve predictions of the future and estimates of the likely behaviour of these sinks. Various
vegetation indices have been proposed for the characterisation of forests including canopy height, canopy area,
Normalised Difference Vegetation Index (NDVI) and Photochemical Reflectance Index (PRI). Both NDVI and PRI are
obtained from a measure of reflectivity at specific wavelengths and have been estimated from passive measurements.
The use of multi-spectral LiDAR to measure NDVI and PRI and their vertical distribution within the forest represents a
significant improvement over current techniques. This paper describes an approach to the design of an advanced Multi-
Spectral Canopy LiDAR, using four wavelengths for measuring the vertical profile of the canopy simultaneously. It is
proposed that the instrument be placed on a satellite orbiting the Earth on a sun synchronous polar orbit to provide
samples on a rectangular grid at an approximate separation of 1km with a suitable revisit frequency. The systems
engineering concept design will be presented.

/pdf/the-design-of-a-space-borne-multispectral-canopy-lidar-to-3ijejv7acz.pdf

James W. Jack

Papers

A Multispectral Canopy LiDAR Demonstrator Project

Development of a laser for differential absorption lidar measurement of atmospheric carbon dioxide

Retinal axons in Xenopus show different behaviour patterns on various glial substrates in vitro.

A robust optical parametric oscillator and receiver telescope for differential absorption lidar of greenhouse gases

The design of a Space-borne multispectral canopy LiDAR to estimate global carbon stock and gross primary productivity