FUNDAMENTALS OF GIS

       Metadata is data about the data. It consists of information that describes spatial data and is used to provide documentation for data products. For example, metadata describes the format, geographic boundary, projection, coordinate system, availability, and cost, etc., of a spatial data set. Metadata is the who, what, when, where, why, and how of spatial data. The key purpose of metadata is to facilitate and improve the retrieval and sharing of information. They are integral part of GIS data and are usually prepared and entered during the data production process. Metadata is important to anyone who plans to use public data for a GIS project.   Metadata is also needed to determine whether a data set will satisfy the user's requirements with respect to spatial resolution and data quality. In the case of remotely sensed images, metadata may include the percentage of cloud obscuring the scene, or whether the scene contains any specific phenomena, such as hur...

  The raster data model represents the Earth’s surface by means of an array of two-dimensional grid cells called pixels. Each pixel has an associated value, which represents the characteristics of the spatial phenomenon. These cells or pixels are used as building blocks for creating points, lines, areas, networks, and surfaces. Raster data represent points by single cells, line by sequences of neighbouring cells, and areas by collection of contiguous cells. The JPEG, BMP, and TIFF file formats are based on the raster data model. All liquid crystal display (LCD) computer monitors are based on raster technology as they are composed of a set number of rows and columns of pixels. Although pixels may be triangles, hexagons, or even octagons, square pixels are most common. Raster models are useful for storing data that varies continuously, such as an aerial photograph, a satellite image, a surface of chemical concentrations, or an elevation surface.  Elements of Raster Data Model...