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Highlights • Evaluates utility of scatterometer data for estimation of urban built-up volume. • Dense Sampling Method-processed scatterometer data are compared to airborne lidar. • Analysis conducted for nine urban areas in the United States. • Strong, linear correlations observed between radar- and lidar-derived datasets. • Results promote three-dimensional approach to land use/land cover analyses. Abstract Accurately mapping urban infrastructure and extent is a high priority for resource management and service allocation as well as for addressing environmental, socioeconomic, and geopolitical concerns. Most available data products only document surficial (two-dimensional) land use and land cover (LULC), yet a substantial component of urban growth occurs in the vertical dimension. Light detection and ranging (lidar) data offer the potential for monitoring three-dimensional (3D) change, but the extreme lack of systematic lidar coverage worldwide inflicts considerable gaps in both spatial and temporal coverage. Satellite scatterometer (radar) data may serve as an alternative data source for characterizing urban growth and development in both the horizontal and vertical directions. The accuracy of these radar-based datasets for estimating building volumes remains to be validated quantitatively. For nine U.S. cities, we test whether scatterometer data can be used to estimate 3D urban built-up volume. We found strong, linear correlations between the lidar-derived and radar-derived building volume estimates for all cities with r2 values as high as 0.98 when using spatial trend analysis. Given the high expense that limits lidar data acquisition to small areas at sporadic points in time, satellite scatterometer data provide a breakthrough method for monitoring both vertical growth and horizontal expansion of cities across the world with a continuous decadal time scale. [ABSTRACT FROM AUTHOR]

A specific example of radar navigation versus the new cooperative surveillance system, known as Automatic Dependent Surveillance-Broadcast (ADS-B), illustrates the shift in air transportation from the current National Airspace System (NAS) to the Next Generation Air Transportation System (NextGen). Drawing from system-of-systems concepts provides insights into exploring the shift. An agent-based model simulates this specific transition from radar navigation to ADS-B navigation and the benefits thereof, specifically in terms of fuel efficiency, as one of many benefits due to NextGen. The results of the simulation indicate a significant fuel savings when ADS-B is used. Furthermore, the modeling approach appears promising for other studies of NextGen. [ABSTRACT FROM AUTHOR]

There is now a large installed base of high-frequency (HF) coastal ocean radars in the United States able to measure surface currents on an operational basis. However, these instruments also have the potential to provide estimates of the spatially variable surface wind field over distances ranging from 10 to 200 km offshore. This study investigates the ability of direction-finding HF radars to recover spatial maps of wind speed and direction from the dominant first-order region radar returns using empirical models. Observations of radar backscatter from the Martha's Vineyard Coastal Observatory HF radar system were compared to wind observations from an offshore tower, finding significant correlations between wind speed and the backscatter power for a range of angles between the wind and radar loop directions. Models for the directional spreading of wind waves were analyzed in comparison to data-based results, finding potentially significant differences between the model and data-based spreading relationships. Using empirical fits, radar-based estimates of wind speed and direction at the location of the in situ wind sensor had error rates of 2 m/s and 60°, which decreased with hourly averaging. Attempts to extrapolate the results to the larger domain illustrated that spatially dependent transfer functions for wind speed and direction appear possible for large coastal ocean domains based on a small number of temporary, or potentially mobile, in situ wind sensors. [ABSTRACT FROM AUTHOR]

High-frequency (HF) surface wave radar has been identified to be a gap-filling technology for Maritime Domain Awareness. Present SeaSonde HF radars have been designed to map surface currents but are able to track surface vessels in a dual-use mode. Rutgers and CODAR Ocean Sensors, Ltd., have collaborated on the development of vessel detection and tracking capabilities from compact HF radars, demonstrating that ships can be detected and tracked by multistatic HF radar in a multiship environment while simultaneously mapping ocean currents. Furthermore, the same vessel is seen simultaneously by the radar based on different processing parameters, mitigating the need to preselect a fixed set and thereby improving detection performance. [ABSTRACT FROM AUTHOR]

The article focuses on the use of radar imaging in monitoring the oil spill in the Gulf of Mexico. It notes that radar being a remote sensing instrument has the capability to image the surface at night and below cloud cover. It mentions that the National Aeronautics and Space Administration (NASA) positioned the uninhabited aerial vehicle synthetic aperture radar (UAVSAR) to monitor the coastline for scientific studies.

The article explores the experiences of American physicist Thomas Kuhn from 1940 to 1951, with a focus on his field training, his accomplishments as a physicist during World War II and his doctoral research. The author emphasizes that Kuhn valued creativity as an inherent element in any intellectual activity, which he applied to his own work since being a young physicist. Kuhn's participation in the development of battlefield radar countermeasures for the U.S. Navy, in conjunction with the U.S. National Defense Research Committee during World War II, is discussed. The author elaborates on Kuhn's doctoral research under the supervision of the American physicist John Hasbrouck Van Vleck.

This article discusses the history of the AEGIS project of the U.S. Navy. It considers the project as the greatest program in the country's history and one of the largest in terms of investment. It identifies the phases of the history and lessons of AEGIS: concept study, engineering development, production, construction, and in-service support. In addition, the article notes the elements of the project, including radar, missile, weapon system and combat system.

Normal near surface radio-frequency (RF) propagation in the littorals across the land–sea boundary is rare due to the land–sea temperature difference, coastline shape, ground cover, urban density, coastal topography, and soil moisture content. The resulting frequent existence of coastal non-standard vertical profiles of refractivity and the resulting RF propagation has a profound impact on the performance of Navy ship-borne radars operating within 100 nm of the shore. In addition, these non-standard RF propagation conditions are spatio-temporally inhomogeneous. These spatial and time dependent propagation conditions and the resulting radar engineering implications cannot be revealed by a single vertical profile of refractivity taken near the ship borne radar. The results from single profile analysis techniques provide no spatiotemporal information and may lead to overly conservative radar design. Mesoscale numerical weather prediction (NWP) is a rapidly maturing technology with a strong operational Navy history that can provide a vertical profile of refractivity every 1 km in the battle space and every hour, up to 48 h, in the future. The Sensor Division at NSWCDD has applied mesoscale NWP for the last 2 years to better understand the performance of prototype radar in realistic four-dimensional (4D) coastal environments. Modern RF parabolic equation models are designed to model specific radar designs and to employ 3D refractivity fields from mesoscale NWP models. This allows for a radar design to be tested in realistic littoral non-standard atmospheres produced by stable internal boundary layers, sea breeze events, and the more rare sub-refractive events. Mesoscale NWP is currently qualitative for this purpose, but a research and development program focused on sea testing of prototype radars is described with the purpose of developing a more quantitative mesoscale NWP technology to support radar acquisition, testing, and operations. [ABSTRACT FROM AUTHOR]

The next generation radar suite will include a radar that has sensitivity far greater than shipboard radars in use today. Most likely the radar will be a multi-faced, solid state, phased array system with each array consisting of thousands of individual radiating elements powered by transmit/receive (T/R) modules. It will likely need to be large, and the demands it makes on ship services will be unprecedented. Its electrical power demands could be larger than the total ship's load for present-day ships. Array size could significantly impact topside design. This paper examines top-level radar system design choices and illustrates the trends in the ship impact of those choices. Radar design options considered are aperture size and shape, coolant operating temperature, number of array faces, and power system architecture. These design options have an effect on the radar system's weight, footprint, power demand, and cooling load. The effects on ship design can be significant. The ship impact analyses consider a radar system that includes ship-provided equipment such as electrical power distribution equipment and chill water plants. An analysis of radar systems, all with the same performance, shows that radar system power demand can change by as much as four megawatts for a notional surface combatant depending upon the radar designer's configuration choices. Radar system weight can vary by more than 100 metric tons. There is a cubic relationship between T/R module power and array face area for a constant sensitivity radar system. This relationship is examined to show that there is often a choice of T/R module power that minimizes radar ship impact. The exact choice of T/R module power depends upon the customer's preferences, the manufacturer's capabilities, and choice of vendors. This paper does not convey any official US government position or US Navy endorsement of any particular radar architecture or design approach. [ABSTRACT FROM AUTHOR]

This study evaluated the potential of an object-oriented approach to forest type classification as well as volume and biomass estimation using small-footprint, multiple return lidar data. The approach was applied to coniferous, deciduous, and mixed forest stands in the Virginia Piedmont, U.S.A. A multiresolution, hierarchical segmentation algorithm was applied to a canopy height model (CHM) to delineate objects ranging from 0.035 to 5.632 ha/average object. Per-object lidar point (per return height and intensity) and CHM distributional parameters were used as input to a discriminant classification of 2-class (deciduous-coniferous) and 3-class (deciduous-coniferous-mixed) forest definitions. Lidar point-height-based and CHM classifications yielded overall accuracies of 89 percent and 79 percent, respectively. Volume and biomass estimates exhibited differences of no more than 5.5 percent compared to field estimates, while showing distinctly improved precisions (up to 45.5 percent). There were no significant differences between accuracies for varying object sizes, which implies that reducing the lidar point coverage would not affect classification accuracy. These results lead to the conclusion that a lidar-based approach to forest type classification and volume/biomass assessment has the potential to serve as a single-source inventory tool. [ABSTRACT FROM AUTHOR]

The article reports on GeoSar's interferometric synthetic aperture radar data (IFSAR) as topographic mapping system in equatorial regions. Geosar technology is developed by NASA's Jet Propulsion Laboratory, U.S. Department of Defense's Defense Advanced Research Projects Agency, Califonia Department of Conservation, and Fugro EarthData, Inc. It cam collect data from an altitude of 40,000 ft. at an airspeed of over 350 mph. Its system operates two frequencies namely X-band and P-band whose wavelengths have a bandwidth of 160 MHz. It also maps drainage features, canopies and wetland habitats in equatorial regions.

Each new generation of remote sensing system typically follows the same evolutionary path from the laboratory to everyday use. For example, the first digital film scanners were actually densitometers with engineering grade servo systems driving them in a pattern across the film with fragile, purpose-built software capturing and converting the data. As the technology matures, it evolves through hardened engineering systems, specialty commercial solutions and, if the market will sustain volume, into a commodity. An inevitable parallel is a declining price in the product being produced by the system. However, how does one emulate this necessary evolution when the volume of the technology is too low to allow it to follow this course? Such was the challenge faced by Fugro EarthData as their GeoSAR system matured from a one-off experimental system developed by NASA's Jet Propulsion Laboratory (JPL) into a production system with commercial throughput and reliability expectations. The avenue chosen by Fugro EarthData was to envelop the unique GeoSAR processing algorithms into the GeoCue enterprise work flow management system. [ABSTRACT FROM AUTHOR]

We produced a landscape scale map of mean tree height in mangrove forests in Everglades National Park (ENP) using the elevation data from the Shuttle Radar Topography Mission (SRTM). The SRTM data was calibrated using airborne lidar data and a high resolution USGS digital elevation model (DEM). The resulting mangrove height map has a mean tree height error of 2.0 m (RMSE) over a pixel of 30 m. In addition, we used field data to derive a relationship between mean forest stand height and biomass in order to map the spatial distribution of standing biomass of mangroves for the entire National Park. The estimation showed that most of the mangrove standing biomass in the ENP resides in intermediate-height mangrove stands around 8 m. We estimated the total mangrove standing biomass in ENP to be 5.6 ⊗ 109 kg. [ABSTRACT FROM AUTHOR]

The Geoscience Laser Altimeter System (GLAS) instrument onboard the Ice, Cloud, and land Elevation Satellite (ICESat) provides a globally distributed elevation data set that is well-suited to independently evaluate the accuracy of digital elevation models (DEMs), such as those produced by the Shuttle Radar Topography Mission (SRTM). We document elevation differences between SRTM C-band 1 and 3 arcsecond resolution DEMs and ICESat 1064 nm altimeter channel elevation data acquired in an areas of variable topography and vegetation cover in the South American Amazon Basin, Asian Tibetan Plateau - Himalayan Mountains, East Africa, western Australia, and the western United States. GLAS received waveforms enable the estimation of SRTM radar phase center elevation biases and variability with respect to the highest (canopy top where vegetated), centroid (distance-weighted average), and lowest (ground) elevations detected within ICESat laser footprints. Distributions of ICESat minus SRTM elevation differences are quantified as a function of waveform extent (a measure of within-footprint relief), SRTM roughness (standard deviation of a 3 ⊗ 3 array of elevation posts), and percent tree cover as reported in the Vegetation Continuous Field product derived from Moderate Resolution Imaging Spectrometer (MODIS) data. SRTM roughness is linearly correlated with waveform extent for areas where percent tree cover is low. The SRTM phase center elevation is usually located between the ICESat highest and lowest elevations, and on average is closely correlated with the ICESat centroid. In areas of low relief and sparse tree cover, the mean of ICESat centroid minus SRTM phase center elevation differences for the five regions examined vary between -3.9 and 1.0 m, and the corresponding standard deviations are between 3.0 and 3.7 m. With increasing SRTM roughness and/or tree cover, the SRTM elevation remains essentially unbiased with respect to the ICESat centroid but the standard deviations of the differences increase to between 20 and 34 m, depending on the region. For the Australia, Amazon, Africa, United States, and Asia regions, including all tree cover and roughness conditions, 90 percent of the SRTM elevations are within 6.9, 11.5, 12.1, 16.8, and 37.1 m of the ICESat centroid, respectively. In vegetated areas, the SRTM elevation on average is located approximately 40 percent of the distance from the canopy top to the ground. The variability of this result increases significantly with increasing SRTM roughness. The results are generally consistent for the five regions examined, providing a method to estimate for any location the correspondence between SRTM elevations and highest, average, and lowest elevations using the globally-available MODIS-derived estimate of tree cover and the measure of SRTM roughness. [ABSTRACT FROM AUTHOR]

The Shuttle Radar Topography Mission (SRTM) generated one of the most-complete high-resolution digital topographic data sets of the world to date. The elevations generated by the on-board C-band sensor represent surface elevations in ‘bare earth’ regions, and the elevations of various scatterers such as leaves and branches in other regions. Elevations generated by a medium-footprint (>10 m diameter) laser altimeter (lidar) system known as NASA's Laser Vegetation Imaging Sensor (LVIS) were used to assess the accuracy of SRTM elevations at study sites of variable relief, and land-cover. Five study sites in Maine, Massachusetts, Maryland, New Hampshire, and Costa Rica were chosen where coincident LVIS and SRTM data occur. Both ground and canopy top lidar elevations were compared to the SRTM elevations. In ‘bare earth ’ regions, the mean vertical offset between the SRTM elevations and LVIS ground elevations varied with study site and was approximately 0.0 m, 0.5 m, 3.0 m, 4.0 m, and 4.5 m at the Maine, Maryland, Massachusetts, New Hampshire, and Costa Rica study sites, respectively. In vegetated regions, the mean vertical offset increased, implying the phase center fell above the ground, and the offset varied by region. The SRTM elevations fell on average approximately 14 m below the LVIS canopy top elevations, except in Costa Rica where they were approximately 8 m below the canopy top. At all five study sites, SRTM elevations increased with increasing vertical extent (i.e., the difference between the LVIS canopy top and ground elevations and analogous to canopy height in vegetated regions). A linear relationship was found sufficient to describe the relationship between the SRTM-LVIS elevation difference and canopy vertical extent. [ABSTRACT FROM AUTHOR]

The Shuttle Radar Topography Mission (SRTM) produced near-global 1″ and 3″ OEMs. The cartographically-derived National Elevation Dataset (NED) provides a mechanism to assess SRTM quality. We compared 12 geomorphometric parameters from SRTM to NED for about 500,000 sample areas over the continental United States. For basic parameters like average elevation or relief, the two data sets correlate very highly. For more derived measures, such as curvature and higher moments (skewness and kurtosis), the correlations are much lower, with some parameters essentially uncorrelated between the two DEMs. Correlations improve after restricting analysis to region with average slopes greater than 5 percent, and the SRTM data set compares more closely to simulated 2″ NED than to 1″ NED. SRTM has too much noise in fiat areas, increasing average slope, while in high relief areas SRTM over smoothes topography and lowers average slopes. The true resolution of 1″ SRTM DEMs proves to be no better than 2″. [ABSTRACT FROM AUTHOR]

The NASA/NGA Shuttle Radar Topography Mission (SRTM) collected interferometric radar data which has been used by the Jet Propulsion Laboratory to generate a near-global topography data product for latitudes smaller than 60°. One of the primary goals of the mission was to produce a data set that was globally consistent and with quantified errors. To achieve this goal, an extensive global ground campaign was conducted by NGA and NASA to collect ground truth that would allow for the global validation of this unique data set. This paper documents the results of this SRTM validation effort using this global data set. The table shown below summarizes our results (all quantities represent 90 percent errors in meters). [ABSTRACT FROM AUTHOR]

The Shuttle Radar Topography Mission (SRTM) successfully acquired terrain elevation data for 80 percent of the Earth's landmass in February 2000. The radar system and data collection scheme designed by NASA's Jet Propulsion Laboratory (JPL) met the global requirements of the U.S. Department of Defense for Level 2 Digital Terrain Elevation Data (DTED®). JPL processed the raw data &to unfinished DTED® 2 and other products that were delivered to two contractors of the National Geospatial-Intelligence Agency. The contractors edited the unfinished DTED® 2, updated the associated products, and generated finished products for distribution. Automated processes were developed by each contractor to identify, delineate and set heights for lakes, rivers, and ocean coastlines in conformance with an extensive set of editing rules created to maintain consistency and uniformity in the final products. The finished DTED® is significantly better than the 16 m vertical accuracy required by the original specification. [ABSTRACT FROM AUTHOR]

The article provides information about the Delta Surface Fill (DSF), a process which replaces the void with fill source posts that are adjusted to the Shuttle Radar Topography Mission (SRTM), an imaging radar system developed by the National Aeronautics and Space Administration and the National Geospatial-Intelligence Agency, values found at the void interface. The DSF method causes the fill to more closely emulate the original SRTM surface while still retaining the useful data the fill contains. The process computes an adjustment of the fill source to the SRTM. The DSF processes was mentioned and offers information on each of the processes. The difference between the DSF and Fill and Feather technique was discussed.

The article presents a review on the origin of the Shuttle Radar Topography Mission project, an advanced imaging radar system in space in partnership with the National Geospatial-Intelligence Agency and the National Aeronautics and Space Administration in the U.S. It mentions several engineers and scientists who have greatly contributed to the success for the development the project including chief engineer Ed Caro, project manager Mike Sander, scientist Gerry Elphingstone and mechanical engineer Bill Layman. The contributions made by the scientists and engineers mentioned was emphasized. It offers a review on how the concept of making the project was made.

Focuses on the lidar industry in the United States. Association between the rate of technological change and Moore's Law; Advice for firms considering entry into the lidar business; Worldwide installed base of lidar systems; Increase in the airborne lidar data file size.