During the last decade many new and improved global geoscience data sets have been evaluated by researchers around the world. While new techniques such as satellite altimetry were developed to ...compute the geoid and marine gravity field to high resolution, existing data sets such as earthquake catalogs and hotspot location lists were enhanced.
These data sets contain invaluable information for every Earth scientist whether the focus is global or regional. With the advent of high‐speed Internet connections, global access to these immense resources is now easy, but actual processing still poses some obstacles.
The Cropland Data Layer (CDL) contains crop and other specific land cover classifications obtained using remote sensing for the conterminous United States. This raster-formatted and geo-referenced ...product has been widely used in such applications as disaster assessments, land cover and land use research, agricultural sustainability studies, and agricultural production decision-making. The traditional CDL data distribution channels include paper thematic maps, email data requests, CD/DVD media, and ftp bulk downloading. To effectively and efficiently meet the growing needs of our customers, CropScape (the name invented for a new interactive Web CDL exploring system) was developed to query, visualize, disseminate, and analyze CDL data geospatially through standard geospatial Web services in a publicly accessible online environment. CropScape not only offers the online functionalities of interactive map operations, data customization and downloading, crop acreage statistics, charting and graphing, and multitemporal change analysis as well in an interoperable manner, but also provides Web geoprocessing services such as automatic data delivery and on-demand crop statistics for uses in other applications. This system delivers dynamic user experiences with its comprehensive capabilities in an open geospatial context, and facilitates delivery and analysis of geospatial cropland information for decision support and various research endeavors. More than 17,000 users around the world have visited CropScape in its first 5months of availability.
Tissot's Indicatrix and regular grids have been used for assessing map projection accuracies. Despite their broad applicability for accuracy assessment, they have limitations in quantifying ...resampling errors caused by map projections. This is due to the structural uncertainty with regard to the placement and pattern of grids. It is also difficult to calculate the absolute amount of resampling error in each projection. As an alternative to traditional testing methods, the use of random points was investigated. Specifically, random point generation, resampling with spherical block search algorithms, resampling accuracy with a perfect grid, and resampling accuracy with eight projections were investigated and are discussed here. Eight global referencing methods were tested: the equal-area cylindrical, sinusoidal, Mollweide, Eckert IV, Hammer-Aitoff, interrupted Goode homolosine, integerized sinusoidal projections, and the equal area global gridding with a fixed latitudinal metric distance. The resampling accuracy with a perfect grid is about 75 percent. Results showed the sinusoidal and the integerized sinusoidal projections and equal-area global gridding to achieve the highest accuracies.
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