14. Associated Data

In the course of processing raster images, several types of associated data files may be created for each image. LAS uses a standard set of extensions to implicitly associate a file with an image. All files in a directory with the same filename but different extensions are considered to be associated. The existence of separate files for the label information gives increased flexibility, simplifies the task of accessing the label information, and allows the image and its associated files to be easily treated as a "data set" for archive and file transfer. The associated files are sequential in organization, making them portable among operating systems. Files may use any extension; however, some standard extensions are used in naming types of files that are frequently used. Some of the file types are:

dltf             Display + Lookup table file
* ddr            Data descriptor records (DDR) file
gof.point        Graphics overlay point file
gof.line         Graphics overlay line file
gof.poly         Graphics overlay polygon file
gof.annot        Graphics overlay annotation file
grid             Geometric mapping grid file
* his            History file
lt               General purpose labeled table file
* img            Image data file
mtp              Merged tie point file
rwt              Resampling weight table file
proj             Projection definition file
stat             Statistics file
tpl              Tie point location file
tps              Tie point selection file
txt              General purpose ASCII file