README.DAT The image files (TM.LAN and TM.IMG) in this subdirectory is a full TM scene that has been compiled by stitching four individual quads together at their common boundaries. This image has been stored in Erdas 7.5 format and Erdas 8.2 format. Please note that the image data are contained in columns 33-6999. Columns 1-32 and columns 7000-7067 contain prefix and suffix data as described below. The prefix data contained in columns 1-32 are described in Table 5-17 of the 1985 User's Guide for Landsat Thematic Mapper Computer- Compatible Tapes. The suffix data contained in columns 7000-7067 are the same as those described in Table 5-17 for columns 4253- 4320. The prefix and suffix data have been included to serve as a method of verifying that the tape data have been transferred properly. Comparing line and band numbers in the prefix (cols 13-20) and suffix (cols 7065-7067) data with what the system believes (using Erdas CURSES for example) allows one to confirm that the data have transferred properly. Note that rows 2984-5965 in the full scene are considered rows 1-2982 in the prefix and suffix data. The statistics in the statistics file (TM.STA) have been generated using all (skip factor of 1) non-zero image data values (cols 33- 6999). README.ANC The files in the \ANCIL subdirectory are the volume descriptor, leader, trailer, supplemental, and null volume files found on Landsat tapes. THE ANCILLARY FILES FROM THIS LANDSAT SCENE ARE IN A DIFFERENT FORMAT FROM OTHER SCENES, AND MAY BE INCOMPLETE. This scene was retrieved from a copy of the original scene. The copy contained ancillary files of different sizes and lengths than the original. THE NAMING CONVENTIONS FOR THE ANCILLARY FILES OF THIS SCENE ARE SLIGHTLY DIFFERENT THAN THOSE OF OTHER LANDSAT TM SCENES. Specifically, each quad has a Header File (H) for each band, and has NO Volume Directory File (V), Trailer File (T), Supplemental Volume Directory File (P), P-Supplemental File (S), or Null Volume Directory File (N). For this scene only, each band of data was preceded by an ancillary file of record length 360 bytes. This file has been designated a "header" file (H) and appears to contain some of the information present in the normal Volume Directory file (V). Following the "header" file is the Leader File (L), which seems to be the same as the normal leader file (see table below). The next file contains the data, the first record of which is the Image File Descriptor (D), the same as on the normal TM scenes. There are NO Trailer files (T), Supplemental Volume Files (P), P-supplemental files (S), or Null Volume Directory Files (N) available for this scene. The following describes the naming convention for this scene: Qntb ||||_ BAND NUMBER |||__ FILE TYPE ||___ QUAD NUMBER |____ Always Q All ancillary file names are prefaced with Q. QUAD NUMBER (n) There are four possible quad numbers in a TM full scene (1-4). Within a TM full scene, the quads are arranged as follows: _______________ | | | | QUAD1 | QUAD2 | |_______|_______| | | | | QUAD3 | QUAD4 | |_______|_______| FILE TYPE (t) The following file types are found on a TM tape: The reference to "Section (S)/Table (T)" in the table below refers to Section/Table numbers in the 1985 User's Guide for Landsat Thematic Mapper Computer-Compatible Tapes. Record Section (S)/ Code Description Length Table (T) V Volume Directory File 360 S5.5 Volume Descriptor Record S5.5.1/T5-4 File Pointer Records S5.5.3/T5-5 L Leader File 4320 S5.5.3,S5.6.1 Leader file Descriptor Record S5.5.3/T5-7 Scene Header Record S5.6.1.1/T5-13 Map Projection Ancillary Record S5.6.1.2/T5-15 Radiometric Calibration Ancillary Record S5.6.1.3/T5-16 D Image File Descriptor Record 4320 S5.5.3/T5-9 T Trailer File 4320 S5.5.3,S5.6.3 Trailer File Descriptor Record S5.5.3/T5-8 Trailer Data Record S5.6.3/T5-19 P Supplemental Volume Directory File 360 S5.5/T5-4 S P-Supplemental File * S5.7 File Descriptor Record 540 T5-10 Band Quality Records 3600 S5.7.1/T5-21 Annotation Record 540 S5.7.1/T5-20 N Null Volume Directory File 360 S5.5 Null Volume Descriptor Record S5.5.1/T5-4 *Note that the P-Supplemental file has been saved as an "unformatted" file such that it is 26280 bytes long with 1 "record" of 540 bytes, 7 "records" of 3600 bytes, and 1 final "record" of 540 bytes. BAND NUMBER (b) Band numbers in a TM scene range from 1-7.