An Esri grid is a raster

Raster graphics

In computer graphics, a raster graphics image, or bitmap, is a data structure representing a generally rectangular grid of pixels, or points of color, viewable via a monitor, paper, or other display medium...

 GIS file format

GIS file formats

A GIS file format is a standard of encoding geographical information into a file. They are created mainly by government mapping agencies or by GIS software developers.Metadata often includes:...

 developed by Esri

ESRI

Esri is a software development and services company providing Geographic Information System software and geodatabase management applications. The headquarters of Esri is in Redlands, California....

, which has two formats:

1. A proprietary
   Proprietary software
   Proprietary software is computer software licensed under exclusive legal right of the copyright holder. The licensee is given the right to use the software under certain conditions, while restricted from other uses, such as modification, further distribution, or reverse engineering.Complementary...
   
    binary
   Binary file
   A binary file is a computer file which may contain any type of data, encoded in binary form for computer storage and processing purposes; for example, computer document files containing formatted text...
   
   format, also known as an ARC/INFO GRID, ARC GRID and many other variations
2. A non-proprietary ASCII
   ASCII
   The American Standard Code for Information Interchange is a character-encoding scheme based on the ordering of the English alphabet. ASCII codes represent text in computers, communications equipment, and other devices that use text...
   
   format, also known as an ARC/INFO ASCII GRID

The formats were introduced for ARC/INFO

ArcInfo

ArcInfo is a full-featured geographic information system produced by Esri, and is the highest level of licensing in the ArcGIS Desktop product line. It was originally a command-line based system...

. The binary format is widely used within Esri programs, such as ArcGIS

ArcGIS

ArcGIS is a suite consisting of a group of geographic information system software products produced by Esri.ArcGIS is a system for working with maps and geographic information...

, while the ASCII format is used as an exchange, or export format, due to the simple and portable ASCII

ASCII

The American Standard Code for Information Interchange is a character-encoding scheme based on the ordering of the English alphabet. ASCII codes represent text in computers, communications equipment, and other devices that use text...

 file structure.

The grid defines geographic space as an array of equally sized square

Square (geometry)

In geometry, a square is a regular quadrilateral. This means that it has four equal sides and four equal angles...

 grid points arranged in rows and columns. Each grid point stores a numeric value that represents a geographic attribute (such as elevation

Elevation

The elevation of a geographic location is its height above a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface ....

 or surface slope) for that unit of space. Each grid cell is referenced by its x,y coordinate location.

ASCII

The format is relatively straightforward: the first six lines indicate the reference of the grid, followed by the values listed in the order they would naturally appear (left-right, top-down). For example, consider a grid, shown to the left. This could be encoded into an ASCII grid file, that would look like:

Grid image	Values	ASCII grid format
			25	75	125	175
275	NA	NA	5	2
225	NA	20	100	36
175	3	8	35	10
125	32	42	50	6
75	88	75	27	9
25	13	5	1	NA

ncols         4

nrows         6

xllcorner     0.0

yllcorner     0.0

cellsize      50.0

NODATA_value  -9999

-9999 -9999 5 2

-9999 20 100 36

3 8 35 10

32 42 50 6

88 75 27 9

13 5 1 -9999

where

• ncols and nrows are the numbers of rows and columns, respectively (represented as integer
  Integer
  The integers are formed by the natural numbers together with the negatives of the non-zero natural numbers .They are known as Positive and Negative Integers respectively...
  
  s);
• xllcorner and yllcorner are the western (left) x-coordinate and southern (bottom) y-coordinates, such as easting and northing
  Easting and northing
  The terms easting and northing are geographic Cartesian coordinates for a point. Easting refers to the eastward-measured distance , while northing refers to the northward-measured distance...
  
   (represented as real number
  Real number
  In mathematics, a real number is a value that represents a quantity along a continuum, such as -5 , 4/3 , 8.6 , √2 and π...
  
  s with an optional decimal point)
• cellsize is the length
  Length
  In geometric measurements, length most commonly refers to the longest dimension of an object.In certain contexts, the term "length" is reserved for a certain dimension of an object along which the length is measured. For example it is possible to cut a length of a wire which is shorter than wire...
  
   of one side of a square cell (a real number); and,
• nodata_value is the value that is regarded as "missing" or "not applicable"; this line is optional, but highly recommended as some programs expect this line to be declared (a real number).

The remainder of the file lists the raster values for each cell, starting at the upper-left corner. These real number

Real number

In mathematics, a real number is a value that represents a quantity along a continuum, such as -5 , 4/3 , 8.6 , √2 and π...

s (with optional decimal point, if needed) and are delimited using a single space character

Space (punctuation)

In writing, a space is a blank area devoid of content, serving to separate words, letters, numbers, and punctuation. Conventions for interword and intersentence spaces vary among languages, and in some cases the spacing rules are quite complex....

.

Binary format

A binary Esri grid is stored in several files contained in at least two directories: the name directory and an info directory, where name has strict naming conventions.