Applications of Shuttle Radar Topography Mission Elevation Data (original) (raw)
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The Shuttle Radar Topography Mission (SRTM), the first relatively high spatial resolution near-global digital elevation dataset, possesses great utility for a wide array of environmental applications worldwide. This article concerns the accuracy of SRTM in low-relief areas with heterogeneous vegetation cover. Three questions were addressed about low-relief SRTM topographic representation: to what extent are errors spatially autocorrelated, and how should this influence sample design? Is spatial resolution or production method more important for explaining elevation differences? How dominant is the association of vegetation cover with SRTM elevation error? Two low-relief sites in Louisiana, USA, were analyzed to determine the nature and impact of SRTM error in such areas. Light detection and ranging (LiDAR) data were employed as reference, and SRTM elevations were contrasted with the US National Elevation Dataset (NED). Spatial autocorrelation of errors persisted hundreds of meters spatially in low-relief topography; production method was more critical than spatial resolution, and elevation error due to vegetation canopy effects could actually dominate the SRTM representation of the landscape. Indeed, low-lying, forested, riparian areas may be represented as substantially higher than surrounding agricultural areas, leading to an inverted terrain model.
Remote Sensing of Environment, 2006
The Shuttle Radar Topography Mission has provided high spatial resolution digital topographic data for most of Earth's volcanoes. Although these data were acquired with a nominal spatial resolution of 30 m, such data are only available for volcanoes located within the U.S.A. and its Territories. For the overwhelming majority of Earth's volcanoes not contained within this subset, DEMs are available in the form of a re-sampled 90 m product. This has prompted us to perform an assessment of the extent to which volcano-morphologic information present in the raw 30 m SRTM product is retained in the degraded 90 m product. To this end, we have (a) applied a simple metric, the so called dissection index (di), to summarize the shapes of volcanic edifices as encoded in a DEM and (b) using this metric, evaluated the extent to which this topographic information is lost as the spatial resolution of the data is reduced. Calculating di as a function of elevation (a di profile) allows us to quantitatively summarize the morphology of a volcano. Our results indicate that although the re-sampling of the 30 m SRTM data obviously results in a loss of morphological information, this loss is not catastrophic. Analysis of a group of six Alaskan volcanoes indicates that differences in di profiles calculated from the 30 m SRTM product are largely preserved in the 90 m product. This analysis of resolution effects on the preservation of topographic information has implications for research that relies on understanding volcanoes through the analysis of topographic datasets of similar spatial resolutions produced by other remote sensing techniques (e.g., repeat-pass interferometric SAR; optical stereometry).
The Shuttle Radar Topography Mission?a new source of near-global digital elevation data
Exploration Geophysics, 2005
The Shuttle Radar Topography Mission (SRTM) has generated a homogeneous near-global digital elevation model (DEM) of the Earth using single-pass radar interferometry. The crew of Space Shuttle Endeavour (STS-99) operated the modified dual-antenna synthetic aperture radar systems for 11 days in February 2000. SRTM acquired both C-band and X-band synthetic aperture radar data, collecting 3D data using a 60-metre mast extending from the shuttle payload bay, containing additional C-band and X-band receiver antennas.
Validation of the Shuttle Radar Topography Mission height data
IEEE Transactions on Geoscience and Remote Sensing, 2000
The Shuttle Radar Topography Mission (SRTM) provided data for detailed topographical maps of about 80% of the Earth's land surface. SRTM consisted of single-pass C-and X-band interferometric synthetic aperture radars (INSARs). In order to utilize SRTM data in remote sensing applications the data must be calibrated and validated. This paper presents The University of Michigan's SRTM calibration and validation campaign and our results using recently acquired C-band SRTM data of our calibration sites. An array of calibration targets was deployed with the intention of determining the accuracy of INSAR-derived digital elevation maps. The array spanned one of the X-band swaths and stretched from Toledo, OH to Lansing, MI. Passive and active targets were used. The passive targets included trihedrals and tophats. The locations in latitude, longitude, and elevation of the point targets were determined using differential GPS. We also acquired U.S. Geological Survey (USGS) digital elevation models (DEMs) to use in the calibration and validation work. The SRTM data used in this study are both Principal Investigator Processor (PI) data, which are not the refined final data product, and the ground data processing system (GDPS) data, which are a more refined data product. We report that both datasets for southeastern Michigan exceed the SRTM mission specifications for absolute and relative height errors for our point targets. A more extensive analysis of the SRTM GDPS data indicates that it meets the absolute and relative accuracy requirements even for bare surface areas. In addition, we validate the PI height error files, which are used to provide a statistical characterization of the difference between the SRTM GDPS and USGS DEM heights. The statistical characterization of the GDPS-USGS difference is of interest in forest parameter retrieval algorithms.
Vegetation height estimation from Shuttle Radar Topography Mission and National Elevation Datasets
Remote Sensing of Environment, 2004
A study was conducted to determine the feasibility of obtaining estimates of vegetation canopy height from digital elevation data collected during the 2000 Shuttle Radar Topography Mission (SRTM). The SRTM sensor mapped 80% of the Earth's land mass with a C-band Interferometric Synthetic Aperture Radar (InSAR) instrument, producing the most complete digital surface map of Earth. Due to the relatively short wavelength (5.6 cm) of the SRTM instrument, the majority of incoming electromagnetic energy is reflected by scatterers located within the vegetation canopy at heights well above the bbald-EarthQ surface. Interferometric SAR theory provides a basis for properly identifying and accounting for the dependence of this scattering phase center height on both instrument and target characteristics, including relative and absolute vertical error and vegetation structural attributes.
Journal of Geophysical …, 2005
1] The first near-global high-resolution digital elevation model (DEM) of the Earth has recently been released following the successful Shuttle Radar Topography Mission (SRTM) of 2000. This data set will have applications in a wide range of fields and will be especially valuable in the Earth sciences. Prior to widespread dissemination and use, it is important to acquire knowledge regarding the accuracy characteristics. In this work a comprehensive analysis of the vertical errors present in the data set and the assessment of their effects on different hydrogeomorphic products is performed. In particular, the work consisted of (1) measuring the vertical accuracy of the data set in two areas with different topographic characteristics; (2) characterizing the error structure by comparing elevation residuals with terrain attributes; (3) assessing a wavelet-based filter for removing speckle; and (4) assessing the effects of vertical errors on hydrogeomorphic products and on slope stability modeling. The results indicate that in the two sites, relief has a strong effect on the vertical accuracy of the SRTM DEM. In the high-relief terrain, large errors and data voids are frequent, and their location is strongly influenced by topography, while in the low-to medium-relief site, errors are smaller, although the hilly terrain still produces an effect on the sign of the errors. Speckling generates deviations in the drainage network in one of the investigated areas, but the application of a wavelet filter proved to be an effective tool for removing vertical noise, although further fine tuning is necessary. Vertical errors cause differences in automatically extracted hydrogeomorphic products that range between 4 and 1090. Citation: Falorni, G., V. Teles, E. R. Vivoni, R. L. Bras, and K. S. Amaratunga (2005), Analysis and characterization of the vertical accuracy of digital elevation models from the Shuttle Radar Topography Mission,
Topography is basic to many earth surface processes. It is used in analyses in ecology, hydrology, agriculture, climatology, geology, pedology, geomorphology, and many others, as a means both of explaining processes and of predicting them through modeling. Our capacity to understand and model these processes depends on the quality of the topographic data that are available. Most countries have much of the land surface covered by cartographic maps at varying scales and of varying accuracies. In most tropical countries, these maps are produced through manual interpretation of stereo pairs of aerial photos, and in some cases the topographic data can be erroneous or missing where cloud was present. With the advent of satellite imagery covering the globe, various global datasets of topography have been produced, of increasingly better resolution, from 10 arc-minutes (approximately 18 km at the equator) to 30 arc-seconds (approximately 1 km at the equator) using the United States Geological Survey (USGS) product, GTOPO30. This topography dataset was widely used for almost a decade, mainly for broadscale assessments. However, the 1-km spatial resolution prevented its use in modeling more detailed earth surface processes, especially in fields such as hydrology, pedology, or small-scale geomorphology. Researchers in these areas had to rely on local maps for the topography. Digitization or photogrammetry, time-consuming and costly processes, was needed to produce high-resolution digital elevation models (DEMs).
2004
Topography is basic to many earth surface processes. It is used in analyses in ecology, hydrology, agriculture, climatology, geology, pedology, geomorphology, and many others, as a means both of explaining processes and of predicting them through modeling. Our capacity to understand and model these processes depends on the quality of the topographic data that are available. Most countries have much of the land surface covered by cartographic maps at varying scales and of varying accuracies. In most tropical countries, these maps are produced through manual interpretation of stereo pairs of aerial photos, and in some cases the topographic data can be erroneous or missing where cloud was present. With the advent of satellite imagery covering the globe, various global datasets of topography have been produced, of increasingly better resolution, from 10 arc-minutes (approximately 18 km at the equator) to 30 arc-seconds (approximately 1 km at the equator) using the United States Geological Survey (USGS) product, GTOPO30. This topography dataset was widely used for almost a decade, mainly for broadscale assessments. However, the 1-km spatial resolution prevented its use in modeling more detailed earth surface processes, especially in fields such as hydrology, pedology, or small-scale geomorphology. Researchers in these areas had to rely on local maps for the topography. Digitization or photogrammetry, time-consuming and costly processes, was needed to produce high-resolution digital elevation models (DEMs).