Digital terrain data file organization
DEM terrain models are usually organised and stored in smaller files called tiles of size 1 x 1 degree. This is convenient way of storing digital terrain data which can be very big in memory size. Each tile file usually has some additional metadata describing inner structure of data, reference geoid used, data coordinates projection, boundaries of the tile and some other data. Tile names usually contain coordinate of the reference geographic point (e.g. lower left corner of the tile). Organization of the tiles is illustrated in following figure.
Sometimes digital terrain data are not organised in data tiles, but can be gathered in a way that one file covers data for one country. This type of data organisation can result in very big files of tens of GB of data.
