The Esri Binary Float Grid filter imports and exports Esri floating point grid files in Esri Spatial Analyst .FLT, .HDR format.
File Description
A grid is a raster data storage format native to Esri. There are two types of grids: integer and floating point. Use integer grids to represent discrete data and floating-point grids to represent continuous data.
Attributes for an integer grid are stored in a value attribute table (VAT). A VAT has one record for each unique value in the grid. The record stores the unique value (VALUE is an integer that represents a particular class or grouping of cells) and the number of cells (COUNT) in the grid represented by that value. For example, if 50 cells have a value of 1 representing a forest, then the VAT would show a VALUE = 1 and COUNT = 50 for each of the 50 cells. Floating-point grids do not have a VAT because the cells in the grid can assume any value within a given range of values. The cells in this type of grid do not fall neatly into discrete categories. The cell value itself is the attribute that describes the location. For example, in a grid that represents elevation data in meters above sea level, a cell with a value of 10.1662 indicates that the location is about 10 meters above sea level.
The HDR file is a binary file. Information stored in the file includes the cell size, type of grid (integer or floating point), compression technique, blocking factor, and tile information.
The coordinate system of a grid is the same as that of other geographic data. The rows and columns are parallel to the x- and y-axes of the coordinate system. Since each cell within a grid has the same dimension as other cells, the location and area covered by any cell is easily determined by its row and column. The coordinate system of a grid is thus defined by the cell size, the number of rows and columns, and the x,y coordinate of the upper left corner. Grids also carry additional information, such as the coordinate system associated with the grid.
File Format
The Esri Binary Float Grid format consists of 2 files: a binary .FLT image file and ASCII .HDR header file with the same filename but different file extension. For example, Test.FLT and Test.HDR.
Grids are implemented using a tiled raster data structure in which the basic unit of data storage is a rectangular block of cells. Blocks are stored on disk in compressed form in a variable-length file structure referred to as a tile. Each block is stored as one variable-length record.
The size of the tile for a grid is based on the number of rows and columns in the grid at the time of creation. The upper limit on the size of a tile is set by the application and is very large (currently set at 4,000,000 x 4,000,000 cells). As a result, most grids used for GIS applications are automatically stored in a single tile. The spatial data for a grid is automatically split across multiple tiles if the size of the grid at the time of creation is larger than the upper limit for the size of a tile.
File Name Extensions
.FLT, .HDR
Import Method
Choose the File | Import command.
Import Options
Specify import options in the Lattice Import Options dialog.
Export Method
Select a lattice or image module and choose the File | Save Data command.
See Also