3.1. General concepts
Index
- Big data
- Data cube
- Equi7Grid
- Granule
- KML
- Map projection
- shapefile
- Spatial resolution
- TIF
| Big data is data sets that are so voluminous and complex that traditional data-processing application software are inadequate to deal with them. Big data challenges include capturing data, data storage, data analysis, search, sharing, transfer, visualization, querying, updating, information privacy and data source. Data sets grow rapidly - in part because they are increasingly gathered by cheap and numerous information-sensing Internet of devices such as smart phones, Earth observation sensors, software logs, etc. |
| A data cube efficiently stores a multi-dimensional array of values. Typically, applied in contexts of big data (i.e. time-series, very high-resolution satellite data), exceeding the hosting computer's main memory. This data can be effectively queried and sliced to extract the required data. |
| The Equi7Grid offers an well defined grid for storing and manipulating EO data, while minimizing data oversampling. Thus being capable of storing data more efficiently without overlapping areas and minimizing raster distortions. Equi7 offers three tiling levels: T6 600 km extent, T3 300 km extent and T1 100 km extent. | ||||||||||||||
| A granule has a fixed size, along with a single orbit and the minimum indivisible partition of a product containing all possible spectral bands. For Sentinel-2 Level-1C and Level-2A, the granules, also called tiles, are 100x100km2ortho-images in UTM/WGS84 projection. The UTM (Universal Transverse Mercator) system divides the Earth's surface into 60 zones. Each UTM zone has a vertical width of 6° of longitude and horizontal width of 8° of latitude. Tiles are approximately 500 MB in size. Tiles can be fully or partially covered by image data. Partially covered tiles correspond to those at the edge of the swath. | ||||||||||||||
| Keyhole Markup Language (KML) is an XML notation for expressing geographic annotation and visualization within Internet-based, two-dimensional maps and three-dimensional Earth browsers. KML was developed for use with Google Earth, which was originally named Keyhole Earth Viewer. It was created by Keyhole, Inc, which was acquired by Google in 2004. KML became an international standard of the Open Geospatial Consortium in 2008. Google Earth was the first program able to view and graphically edit KML files. Other projects such as Marble have also started to develop KML support. | ||||||||||||||
A map projection is a systematic transformation of the latitudes and longitudes of locations from the surface of a sphere or an ellipsoid into locations on a plane. Maps cannot be created without map projections. All map projections necessarily distort the surface in some fashion. Depending on the purpose of the map, some distortions are acceptable and others are not; therefore, different map projections exist in order to preserve some properties of the sphere-like body at the expense of other properties. The list below summarizes the most common map projections used in Austria.
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| The shapefile format is a popular geospatial vector data format for geographic information system software. It is developed and regulated by Esri as a (mostly) open specification for data interoperability among Esri and other GIS software products. The shapefile format can spatially describe vector features: points, lines, and polygons, representing, for example, water wells, rivers, and lakes. Each item usually has attributes that describe it, such as name or temperature. | ||||||||||||||
In remote sensing, spatial resolution or ground sampling distance is typically limited by diffraction, as well as by aberrations, imperfect focus, and atmospheric distortion. The ground sample distance (GSD) of an image, the pixel spacing on the Earth's surface, is typically considerably smaller than the resolvable spot size.
Example of Landsat 8's different spatial resolutions (source: https://landsat.gsfc.nasa.gov/landsat-8/landsat-8-overview/) | ||||||||||||||
| TIF stands for Tagged Image File. These files are also known as TIFF files, or "Tagged Image File Format" files. The files that contain the .tif file extension contain high-quality graphic images. These files are used for storing raster graphics images, popular among graphic artists, the publishing industry and photographers. TIFF is widely supported by scanning, faxing, word processing, optical character recognition, image manipulation, desktop publishing, and page-layout applications. |
