The LAS environment consists of the following components or interfaces to other software packages:
LAS 7.4 has been installed on computer systems that support the following configurations:
Since LAS is written in both Fortran and C, both these compilers need to be available. Two Xwindows-based programs, xid and tiepts, need X11R4 and Motif 1.1 or higher to build.
The LAS applications modules are integrated under a unified, user-friendly, menu-driven interface for novice users with extensive on-line help capabilities, and a command language interface for experienced users. This interface is created through the "Classic" (non-Xwindows) subset of the Transportable Applications Environment (TAE), developed by Century Computing, Inc., under contract to GSFC.
To assist the user, TAE provides both a menu-driven and a command-language mode. In addition, TAE allows the user to access the host operating system's command interpreter (shell commands on UNIX systems) while under TAE so that the user can utilize capabilities of the host operating system without exiting from TAE. More specific usage will be discussed in later sections.
LAS provides a catalog manager which will list the on-line images, associated files, and other files under a user's computer account. LAS uses a series of extensions to distinguish between the different files that may appear. These extensions are discussed in Section 4.3.1. The host name for a LAS image is a combination of the name as specified by the user in a LAS module and the extension. Consequently, it is easy for the user to identify the on-line images by using either a LAS catalog manager module or a host computer file listing utility. However, the LAS catalog manager module will provide to the user the information on the number of lines and samples, bands, etc.; while the host computer utility will simply list the filenames. The LAS catalog manager also provides the ability to delete images, associated files, or general files. All the LAS catalog manger modules recognize wild cards and aliases. Wild cards and aliases are described in Section 4.2.
LAS provides a complete display module, xid, which allows users to display image data, manipulate it, and save the modified images or enhancement tables to disk. It also allows the user to perform mensuration on the displayed image.
The LAS application modules provide the user with the tools necessary to perform various analyses and manipulations of the image data such as classification, clustering, film processing, Fourier transforms, geometric registration, image repair, radiometric correction, and manipulation of image statistics. There is a separate Users Guide for each module. There are two indices to these users guides, arranged alphabetically or by functional category. Typical processing scenarios using some of these modules are presented in Section 5.
The original concept behind LAS was to provide an image processing/analysis system for use with remotely sensed data. Requirements also existed to provide the user community with statistical, geographic information system (GIS), and data base management system (DBMS) capabilities. User preference and the availability of commercial packages to provide these capabilities allowed the original LAS designers to not "reinvent these capabilities" under LAS but rather to develop a flexible, simple interface capability which would allow the transfer of data between LAS and any of these other packages. The interface method selected was a file called a labeled table (LT). LAS modules that interface to one of these packages will write information to the LT, and software can be written which will transfer the data between the LT and a specific DBMS, statistics package, or GIS. Also, any of the modules in LAS that have the print parameter will also create an ASCII file containing the results of operation. These files may also be used as input into other software packages. There also exists the ability to convert ASCII files to and from the LT.
The Large Area Mosaicking System (LAMS) was first developed by the Jet Propulsion Laboratory (JPL) for use in mosaicking planetary images. It was acquired by EDC from JPL for mosaicking Landsat images. It was not originally under LAS but has since been converted to be part of the LAS system. It allows a user to geometrically and radiometrically correct images creating mosaics that can then be enhanced or processed by other LAS modules. It is flexible enough to handle imagery from rectified aerial photography to NOAA's Advanced High Resolution Radiometer (AVHRR) sensor. A more detailed description of LAMS is available in the Overview of the Large Area Mosaicking System (LAMS) of the LAS documentation set. LAMS is not normally distributed with LAS unless specificly requested.
Included in the LAS are several raster GIS modules which allow a user to perform such operations as overlay, renumbering, spread, and neighborhood analysis. These modules provide some primitive capabilities, but the requirement to have access to a more complete GIS required interfaces to be developed. Earlier versions of LAS had an interface to the Map Overlay and Statistical System (MOSS), a geographic information system originally developed for the Western Energy and Land Use Team (WELUT) of the United States Fish and Wildlife Service. The current version of LAS allows data to be exchanged with the ARC/INFO system developed by the Environmental Systems Research Institute (ESRI). This interface is through the LT for ARC coverages and via a LAS module for ARC/INFO raster or single variable file (SVF) images. These interface routines are not normally part of a LAS distribution. Conversions to and from ARC/INFO raster (GRID) files are supported at PSU (programsarc2las and las2arc.)
LAS provides some capabilities to perform certain types of statistical analysis such as maximum likelihood classification. However, for more complex statistical analysis such as analysis of variance, LAS provides the ability to transfer data to and from statistics packages. Either the LT or the ASCII files may be created or ingested in LAS. Two commercial statistics packages that have been used in conjunction with LAS are the Statistical Package for the Social Sciences (SPSS) and the SAS. Both packages are capable of information storage and retrieval, data modification, report writing, statistical analysis, and file handling. Interfaces with LAS are through LT formatted output files from several LAS modules (for example, intersect).
The need to handle not only raster and vector data but also tabular data such as soil attributes has meant that LAS needed to have an interface to a data base management system (DBMS), in this case, a relational DBMS. In a relational DBMS, data is stored in tables which are called relations. One or more relations make up a data base. A schema defines each relation in the data base. The rows in the relation are called rows, while the columns are called attributes. These tables can be created, modified, deleted, and combined using DBMS commands. Most DBMS have a query language and allow the user to perform relational operations on the data base. They also have a help and "report writer" capability as well as the capability to unload the data base for transfer between computers.
Some of the LAS application modules, such as intersect and tab2ras, interface to the DBMS through the LT files.
LAS has been designed to allow image sizes large enough for users to conduct research on global data sets or to handle the new multi-band sensors. The image size and number of bands allowed are established by the system manager when the system is installed. LAS also makes use of system globals to set processing features and limitations. The LAS system was designed to allow the following: