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GENERAL INFORMATION AND DIRECTORY STRUCTURE RAMS - Radarsat Antarctic Mapping System. Software developed by the Vexcel Corporation to process the Radarsat image data. Block- Blocks comprise ~150-200 frames that have been geocoded, terrain corrected, radiometrically balanced and mosaicked together. See Block Processing Stage below for additional information. Tile- Tiles are made up of Blocks that have undergone Block to Block grand geometric and radiometric balancing. There are 93 tiles which make up Antarctica. See the section on TILE & SUB-TILE NAMING CONVENTIONS for additional information. Tile Products- are the Final RAMS Products that will be distributed to the community. Final Tile Products can have a file size for 16-bit image products up to 900Mb. A final tile product contains several layers of data: SAR imagery, shadow/layover/incidence angle masks, digital elevation data, imagery indices. Some utility programs are also provided which may be useful for interpreting the image data. All of these things are distributed in seven directories: ANGLES.DIR - shadow / layover / incidence angle masks DEMINDEX.DIR - DEM index table and support files DEMS.DIR - DEMs and DEM index values IMAGES.DIR - SAR imagery indices IMGINDEX.DIR - SAR image index table and support files INDICES.DIR - SAR imagery indices MASTER.TXT - list of all sub-tiles in the tile PROGRAMS.DIR - utility programs README.TXT - This document Other data files: Tiles.nam - Text file cross referencing database structure with Tile Name ie: til_89 SP_20-20 til_90 SP_21-21 tile_name.gif- Graphic showing tile distribution and tile names SS_00-00.gif - Graphic showing the image data contained in that specific tile. SubTile-A subtile is a uniform raster binary image of a standard dimension (2048x2048 for 16-bit products) that make up a Tile. A tile could contain as many as 98 subtiles depending on the geometry/size of the Tile and the amount of data coverage contained in the tile. See the section on TILE & SUB-TILE NAMING CONVENTIONS for additional information Final- The term "Final" indicates that the SAR data are derived from blocks which have been individually processed then mosaicked together in a step called the "Grand Adjustment". In general, a block, which consists of a collection of contiguous frames, is formed by the following processing steps: PROCESSING STEPS Block Processing Stage: SAR data ingest (level 1 products) Ground control points located Tie points collected between images Block adjustment (to correct relative and absolute errors in state vectors) Orthorectification (terrain distortion removal and, optionally, radiometric corrections for pixel size) Tie points collected between orthorectified images Radiometric balancing (for radiometric seam removal) Geometric warp (optional, for residual geometric seam removal) Block mosaic formation Reset shadow / layover areas to no-data Mosaic fill-in with shadow / layover imagery Preliminary product formation (optional) Extraction of image chips around block boundaries for block-to-block tie point computation in the Tile Processing Stage. Tile Processing Stage: Grand Adjustment: done after all blocks in the mosaic have been processed. The purpose of the adjustment is to remove block-to-block geometric and radiometric seams. Seam removal requires the computation of tie points from the image chips extracted from each block. During this process an optimal 16 to 8-bit look up table is also computed if the final product is 8 bit. Final tiles are then produced from block data by applying the seam removal and radiometric equations derived from the block-to-block tie points. If the output type is 8 bit, the 16 to 8-bit look up table is also applied. TILE & SUB-TILE NAMING CONVENTIONS For RAMS, each Tile roughly corresponds to an area delineated by the boundaries of the International Map of the World 1:1,000,000 map sheets for Antarctica. The tile naming convention used is taken from the same source. (See also the Antarctic Digital Database documentation from the British Antarctic Survey.) For other uses of this system, a tile is defined as any arbitrary collection of sub-tiles in a given map projection and for a given area. The list of sub-tiles comprising a tile is given in the MASTER.TXT file. This file contains the list of sub-tile names and their minimum and maximum corner x, y values in map coordinates (Polar Stereographic using a WGS84 ellipsoid). For all map products supported by this system, each sub-tile follows the following naming convention: Each sub-tile is the same size (51.2 km on a side or 2048x2048 pixels) with four sub-tiles residing around the origin of the map projection. The common corner is located at the South Pole (for RAMS) or (0,0). From the origin to the right, the subtiles are named E001..., E002..., etc. >From the origin to the left, the subtiles are named W001..., W002..., etc. >From the origin to the top, the subtiles are named ...T001, ...T002, etc. >From the origin to the bottom, the subtiles are named ...B001, ...B002, etc. FILE CONTENTS AND THEIR USE "CD.C" - This file contains utility functions used by the programs listed above. "CD.H" - The header file for CD.C. "README.TXT" - this file "MASTER.TXT" - This file contains a list of all sub-tiles in the tile (including each sub-tile name and corner coordinates). The pixel spacings for imagery, shadow / layover / incidence angle masks, DEMs, and index tiles are given. Map projection information is also provided. To look up the full name of the projection, see the file "PJ_LIST.H" in the PROGRAMS.DIR/PROJ.DIR directory. "ANGLES.DIR/
.SLI" - These are the shadow/layover/incidence angle sub-tiles. These are 8-bit unsigned integer binary raster images. Each sub-tile is of dimension 512 x 512 (100 meter pixel spacings). The encoding is as follows: 0 : shadow region 1..253 : incidence angle = 90 - < 8-BIT DATA NUMBER > 254 : layover region 255 : no-data "DEMS.DIR/ .DEM" - These are the DEM sub-tiles. They are headerless, 16-bit unsigned integer binary raster images. For RAMS, each sub-tile is 256 x 256. -9999 signifies no-data values for the 16-bit product. "DEMINDEX.DIR/ .DIN" - This directory contains text files indexing the data source contributing to the construction of the DEM ie: 0 = "ADD Contours & Elevation Points, ERS_1 Altimeter Ice Mode & Ocean Mode" "IMAGES.DIR/ .IMG" - These are the image sub-tiles. They are headerless, 16-bit unsigned integer binary raster images. For RAMS, each sub-tile is 2048 x 2048. To convert each DN value back to sigma0, use the program GETSIG0.C in the PROGRAMS.DIR directory. -9999 signifies no-data values for the 16-bit product. "IMGINDEX.DIR" - This directory contains files documenting the processing history of the images. The following files are included: "BLOCKS.KEY" contains a list of blocks contributing to the tile and the associated coefficients used to radiometrically and geometrically adjust the blocks. "FRAMES.KEY" contains a list of frames contributing to the tile and for each the associated GCP's, Ephemiris and radiometric balancing coefficients. "INDEX.TBL" - This is the index table for the entire tile. The index table contains rows of entries. The first column contains the index value. The second column contains the Orbit and Frame numbers. "INDICES.DIR/ .IDX" - These are the index sub-tiles. They are stored as 8-bit raster images of dimension 512 x 512 (100 meter pixel spacings). Each DN value corresponds to an entry in the index table found in the IMGINDEX.DIR/INDEX.TBL. "PROGRAMS.DIR": The following C programs are provided for final tile products. All programs contain documentation on compiling and linking in their headers. A Makefile is also provided to help users build and link the programs properly. "GEO2MAP.C" - This program converts latitude and longitude to x, y map coordinates. The projection name and ellipsoid are read from the MASTER.TXT file. GEO2MAP -h GEO2MAP: To convert (lat,lon) to map (x,y) Usage: GEO2MAP [,] [-h] - (help) print usage [-db] - (debug) print detailed info example:GEO2MAP -67.56622 -68.11323 -2289977.407354, 919950.84983 This program can be converted to a function. Instructions for doing so are provided within the header comments. "MAP2GEO.C" - This program converts x, y map coordinates to latitude, longitude. The projection name and ellipsoid are read from the MASTER.TXT file. MAP2GEO -h MAP2GEO: To convert map (x,y) to (lat,lon) Usage: MAP2GEO [,] [-h] - (help) print usage [-db] - (debug) print detailed info example:MAP2GEO -2289977, 919950 -67.56622, -68.11324 This program can be converted to a function. Instructions for doing so are provided within the header comments. "TILE2MAP.C" - This program converts RAMS tile name, line (col), & sample (row) to RAMS map x,y coordinates TILE2MAP -h usage: TILE2MAP [-h] - (help) print usage [-db] - (debug) print detailed info [-l] - default: 1st line in subtile [-s] - default: 1st pixel in line [-p] - default: 25 meters square [-t] - default: 51200 meters square ie: TILE2MAP W045T018 -l 50 -s 150 map (x, y) = (-2300275.000000, 920375.000000) "MAP2TILE.C" - This programs gives the Subtile name, and column and row which a specified map x,y coordinate is contained. MAP2TILE -h Usage: MAP2TILE [,] [-h] - (help) print usage [-db] - (debug) print additional info [-n] - name convention to use default: T,B,E,W (Top, Bottom, East, West) [-p] - default: 25 meters square [-t] - default: 51200 meters square MAP2TILE -1968800 -104000 W039B003 line: 65, sample: 1121 "MERGEMAP.C" -This programs generates a mosaic of SAR image subtiles within an area specified by center point and size. The mosaic includes entire subtiles so the output size may be different from the size specified. The -hdr option will generate a header text file containing samples, lines (cols,rows) the upper right and lower left x,y map coordinates. At this time only SAR image subtiles can be merged using this routine. Usage: MERGEMAP -l -size -path <...> -fout <...> -hdr [-h -db] Where: -l - center point latitude and longitude -size - dimensions of output image in meters -path <...> - path to the base product directory -fout <...> - path/name of the output image -h - (help) print usage -hdr - output header file (.h) for image -db - debug info ie: MERGEMAP -l -67.5 -68.1 -size 150000 150000 -path ../ -fout FILE.OUT -hdr "GETSIG0.c" - This program prints to standard out the "original" pixel value in power for a pixel at image location (x, y) in map coordinates. It inverts the geometric adjustment applied during block to block processing and the radiometric balancing applied during both block processing block to block processing and converts the 16-bit value to power. It does not invert any radiometric corrections made during orthorectification due to terrain. There is also some uncertainty in the inversion as the index tile used to determine which pixels come from which images is provided at a lower resolution than the imagery itself. At this time sigma0 is calculated on a pixel by pixel basis. GETSIG0 -h GETSIG0: To obtain original sigma nought value at (x,y) Usage: GETSIG0 [,] [-h] - (help) print usage [-db] - (debug) print detailed info ie: GETSIG0 -2404300 1197000 Sigma Nought (-2404300.000000, 1197000.000000): -21.211612 This program can be converted to a function. Instructions for doing so are provided within the header comments. "MAKEFILE" - A Unix Makefile for the programs. Make libproj first: Go to the PROGRAMS.DIR/PROJ.DIR/ and type "make" Then build the individual programs: Go to the PROGRAMS.DIR/ and type "make -f MAKEFILE" "PROJ.DIR/*" - This directory contains the map projection library source code used by RAMS. The header file "PROJECTS.H" is included in "CD.H". A "MAKEFILE" is provided to build the map projections library libproj. The default compilation flags are -I. to indicate that header files are stored locally. If you wish to add any flags, set the environment variable VX_DEFS to the desired additional flags. If you need to remove or modify any of the flags, modify the definition of CFLAGS in the Makefile. Note that the library must be linked with the standard C math library (see LIBS in the Makefile). GETTING STARTED: 1) The extracted Tile data from DVD will have the following directory structure: til_00/cd/ANGLES.DIR (shadow/layover/incidence angle masks) DEMINDEX.DIR (DEM index table and support files) DEMS.DIR (DEMs and DEM index values) IMAGES.DIR (SAR imagery, 16-bit binary) IMGINDEX.DIR (SAR image index table and support files) INDICES.DIR (SAR imagery indices) MASTER.TXT (sub-tile name and corner coordinates) PROGRAMS.DIR (utility programs) README.TXT Tiles.nam - Text file cross referencing database structure with Tile Name ie: til_89 SP_20-20 til_90 SP_21-21 tile_name.gif- Graphic showing tile distribution and tile names. SS_00-00.gif - Graphic showing the image data contained in that specific tile. **See Tiles.nam file to co-register the database til_00 with the actual tile name (ie: til_53 -> SR_13-14, til_54 -> SR_15-16, etc.) **See tile_name.gif for the Tile name scheme distribution. 1) Go to til_00/cd/PROGRAMS.DIR/PROJ.DIR and type "make" to create the projections library. 2) Go to til_00/cd/PROGRAMS.DIR and type "make -f MAKEFILE" to create all the utilities.