RAMP Data
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RAMP AMM-1 SAR Image Mosaic of Antarctica:
README file for 25 m tiles
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.
