What is a HDR file?
An HDR file is a GIS header file that contains header information for a Band interleaved by line (.BIL) file. It describes the image data and has the same name as that of the image file. An HDR file comprises of a set of entries, each of which describes a particular attribute of the image. The HDR file describes the layout and formatting of the BIL file for translation to real world coordinates in combination with a separate georeferencing file.
HDR File Format
HDR files are saved in ASCII text file format. It contains a set of entries where each entry describes a particular attribute of the image. Each HDR file has the following format:
<keyword> - It indicates the particular attribute that is being set
<value> - It is the value to which the attribute is being set
There is no limitation on the order of the entries in the header. However, each entry must be on a separate line of the line to comply with the parsing method used by HDR readers.
Summary of Keywords used in HDR File
|nrows||any integer > 0||none|
|ncols||any integer > 0||none|
|nbands||any integer > 0||1|
|nbits||1, 4, 8, 16, 32||8|
|byteorder||I = Intel;M = Motorola||same as host machine|
|layout||bil, bip, bsq||bil|
|skipbytes||any integer ≥ 0||0|
|ulxmap||any real number||0|
|ulymap||any real number||nrows - 1|
|xdim||any real number||1|
|ydim||any real number||1|
|bandrowbytes||any integer > 0||smallest integer ≥ (ncols x nbits) / 8|
|totalrowbytes||any integer > 0||for bil: nbands x bandrowbytes;for bip: smallest integer ≥ (ncols x nbands x nbits) / 8|
|bandgapbytes||any integer ≥ 0||0|