In this paper we present a description of a new multispectral airborne mapping light detection and ranging (lidar) along with performance results obtained from two years of data collection and test ...campaigns. The Titan multiwave lidar is manufactured by Teledyne Optech Inc. (Toronto, ON, Canada) and emits laser pulses in the 1550, 1064 and 532 nm wavelengths simultaneously through a single oscillating mirror scanner at pulse repetition frequencies (PRF) that range from 50 to 300 kHz per wavelength (max combined PRF of 900 kHz). The Titan system can perform simultaneous mapping in terrestrial and very shallow water environments and its multispectral capability enables new applications, such as the production of false color active imagery derived from the lidar return intensities and the automated classification of target and land covers. Field tests and mapping projects performed over the past two years demonstrate capabilities to classify five land covers in urban environments with an accuracy of 90%, map bathymetry under more than 15 m of water, and map thick vegetation canopies at sub-meter vertical resolutions. In addition to its multispectral and performance characteristics, the Titan system is designed with several redundancies and diversity schemes that have proven to be beneficial for both operations and the improvement of data quality.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Ground-based LIDAR (also known as laser ranging) is a novel technique that may precisely quantify fuelbed characteristics important in determining fire behavior. We measured fuel properties within a ...south-eastern US longleaf pine woodland at the individual plant and fuelbed scale. Data were collected using a mobile terrestrial LIDAR unit at sub-cm scale for individual fuel types (shrubs) and heterogeneous fuelbed plots. Spatially explicit point-intercept fuel sampling also measured fuelbed heights and volume, while leaf area and biomass measurements of whole and sectioned shrubs were determined from destructive sampling. Volumes obtained by LIDAR and traditional methods showed significant discrepancies. We found that traditional means overestimated volume for shrub fuel types because of variation in leaf area distribution within shrub canopies. LIDAR volume estimates were correlated with biomass and leaf area for individual shrubs when factored by species, size, and plant section. Fuelbed heights were found to be highly variable among the fuel plots, and ground LIDAR was more sensitive to capturing the height variation than traditional point intercept sampling. Ground LIDAR is a promising technology capable of measuring complex surface fuels and fuel characteristics, such as fuel volume.
Airborne laser scanning (ALS) is a remote-sensing technique that provides scale-accurate 3D models consisting of dense point clouds with x, y planimetric coordinates and altitude z . Using ALS, very ...high-resolution (VHR) digital surface models (DSMs) have been widely used for commercial and scientific applications since the early 1990s. Although there is widespread usage, there has been little comprehensive investigation of quality control for ALS DSMs in the literature, as most studies have been limited to assessing point-based vertical accuracy. This article is dedicated to investigating the quality of ALS DSMs for different land classes using statistical and visual approaches based on absolute and relative vertical accuracy metrics. Rather than a limited number of ground control points (GCP), the model-to-model-based approach is applied and DSMs derived from terrestrial laser scanning (TLS) point clouds that have around 5 mm absolute and 3 mm relative geolocation accuracy were used as the reference data for comparison. The results demonstrate that in open, grass, and building land classes, the ALS DSMs reached both standard deviation (σ) and normalized median absolute deviation (NMAD) of 3–5 cm after the elimination of any systematic biases. This result sufficiently satisfies the vertical accuracy requirements for 1/1000-scale topographic maps determined by National Digital Elevation Program (NDEP) specifications. In tall vegetation, a higher number of discrepancies larger than 0.5 m exist, reversing the relation between σ and NMAD. These vegetation errors also do not appear to be normally distributed. As an additional investigation, the performance of ALS DEMs under dense high-vegetation areas was assessed. These under-canopy ALS DEMs, created using only classified ground returns, offer both σ and NMAD of 12–14 cm, a performance level that is difficult to achieve under-canopy using photogrammetric techniques.
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In this paper we present results obtained with a new single-wavelength LiDAR sensor which allows seamless sub-meter mapping of topography and very shallow bathymetry in a single pass. The National ...Science Foundation supported National Center for Airborne Laser Mapping (NCALM) developed the conceptual design for the sensor that was built by Optech Inc. The new sensor operates at a wavelength of 532 nm and is fully interchangeable with an existing 1064 nm terrain mapping sensor operated by NCALM, connecting to the same electronics rack and fitting into the same aircraft mounting assembly. The sensor operates at laser pulse repetition frequencies (PRFs) of 33, 50 and 70 kHz, making it possible to seamlessly map shallow water lakes, streams, and coastal waters along with the contiguous terrain, including rural and urban areas. This new sensor has been tested in a wide variety of conditions including coastal, estuarine and fresh water bodies, with water depths ranging from 20 centimeters to 16 meters, with varying benthic reflectivity and water clarity. Observed point densities range from 1-4 points/m 2 for terrestrial surfaces and 0.3-3 points/m 2 for sub water surfaces in a single pass, and double these values when the data are collected with 50% side swath overlap, a minimum standard for NCALM's airborne LiDAR surveys. The seamless high resolution data sets produced by this sensor open new possibilities for geoscientists in fields such as hydrology, geomorphology, geodynamics and ecology.
We propose combining a forward model based support vector regression and the semianalytical radiative transfer model to determine shallow water characteristics. The derived water depths were compared ...to both LiDAR derived water depths and field measured water depths. The bathymetry results show that both LiDAR and hyperspectral imagery are unable to retrieve water depth for deeper water (>7 m) due to the water attenuation. Fusion was also performed with the LiDAR bathymetry as a constraint on the hyperspectral imagery; the constraint varies the estimated water characteristics but we were not able to independently assess the performance because no measurements of water column characteristics were available. The retrieved hyperspectral bathymetry yielded a standard deviation of 20 cm when compared to LiDAR bathymetry.
Pulsed Light Detection And Ranging (LiDAR) intensity has commonly been used as a measure of relative reflectance of materials to aid in both point classification and object identification. However, ...as LiDAR systems use a single light wavelength, the intensity has had little value for advanced material classification. With the advent of multispectral LiDAR systems, it may be possible to use the LiDAR intensity in multiple spectral bands to assist in automated target recognition. Towards this end, we present a comparison between LiDAR intensity images and passive reflectance from a hyperspectral imaging system in the same spectral bands. Although qualitatively the LiDAR intensity and hyperspectral imagery show good agreement, a quantitative analysis shows there are significant deviations between their respective reflectance measurements, particularly for complex features such as trees.
En Mayo del 2012, después de más de un año de investigación y planeación, un grupo dirigido por el cinematógrafo Steve Elkins con el respaldo de Bill Benenson, y Garry Spire, realizó el primer mapeo ...exploratorio de la Mosquitia Hondureña utilizando tecnología LiDAR abordo un avión bimotor Cessna 337. La tecnología Li- DAR, que es un acrónimo en Inglés para Light Detection and Ranging, es también conocida como Radar Óptico o Radar Laser y utiliza pulsos laser para generar mapas tridimensionales de la superficie terrestre. En general, equipos LiDAR actuales permiten detectar múltiples retornos para cada pulso emitido a medida que estos se propagan a través de aberturas en las coronas de los árboles y demás vegetación hasta el terreno debajo de ella. A través de filtros morfológicos es posible clasificar los retornos como provenientes de vegetación o del suelo, lo que permite separar los retornos del suelo revelando lo que el bosque oculta. La Mosquita provee las condiciones más difíciles para probar las capacidades de la tecnología LiDAR.La planeación, recolección, procesamiento y análisis preliminar de los datos LIDAR fue efectuada por técnicos del centro de investigación de ciencias e ingeniería de sistemas de Geopercepción de la Universidad de Houston y el Centro Nacional para el Mapeo Laser Aéreo de la Fundación Nacional para la Ciencia. El mapeo se enfocó en varias aéreas dentro de una extensión de jungla de aproximadamente 1000 km² en el departamento de Gracias a Dios. Los planes de vuelo y el equipo fueron configurados para lograr la máxima penetración a través de la vegetación. Emitiendo más de 20 pulsos/m² y obteniendo aproximadamente 31 retornos/m² de los cuales solo 1 o 2 corresponden al suelo. Los modelos digitales de elevación de terreno revelan debajo de la espesa vegetación una exuberante topografía y una muy compleja hidrografía. Mas interesante, muestran una extensa modificación antropogénica del terreno, en lo que parece ser restos arqueológicos.Revista Ciencias Espaciales, Volumen 8, Número 1 Primavera, 2015; 260-276
The capability of airborne LiDAR scanners (ALS) to record returns from the ground surface and other targets occluded by forest canopies has been of great value for geosciences and military ...operations. In this paper we present preliminary results from efforts aimed to characterize different types of forest canopies and to assess the quantity and quality of potential ground returns obtained through different configurations of small footprint airborne mapping LiDAR systems. The final goal of this work is to provide a methodology that allows for the quantification of the "openness" of a forest canopy and procedures to determine the best configuration of ALS systems that ensures maximum detection of ground returns independent of the many different system designs currently available.
Over the last two decades airborne terrestrial and bathymetric LiDAR systems have experienced exponential development. However, the design criteria for either terrestrial or bathymetric systems have ...created a gap where these systems are not operational. This gap is in the interface and overlap of land surface and very shallow water (<; 5 m) bodies such as lakes, lagoons, rivers, intracoastal waterways, and the surf zone. These areas are of high interest for geoscientists and engineers, and mapping this topography at high resolution in a single pass with a single system until now has been unachievable. In this paper we present a new LiDAR system that integrates design characteristics of terrestrial and bathymetric systems which enables the high resolution topographic mapping of land and shallow water bathymetry in a single pass. We will also present early results from test flights of the system under different conditions and outline future work.
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