DEM parameter file (for structure definition see typedef_DIFF.h)
NAME
DEM_par - Digital elevation model (DEM) / MAP parameter file
(ASCII) used by GAMMA DIFF&GEO software.
SYNOPSIS
non executable
EXAMPLE and PARAMETER DEFINITIONS
The format of the DEM parameter file is different for different
DEM projections. Supported DEM projections are:
| Keyword | Projection |
| EQA | Equiangular |
| UTM | Universal Transverse Mercator |
| TM | Transverse Mercator |
| OMCH | Oblique Mercator (Switzerland) |
| LCC | Lambert Conformal Conic (France) |
| PS | Polar Stereographic |
| SCH | SAR coordinates used at JPL |
| PC | Polyconic Projection |
| AEAC | Albers Equal Area Conic |
The parameter definitions are not the same for the different coordinates, but most parameters are common to all projections.
The parameters contained in the DEM/map parameter file are
structured into:
- general parameters
- ellipsoid parameters
- datum parameters
- projection parameters.
Part 1: General Parameters
| Keyword | Example | Definition |
| title | Death Valley UTM DEM | Title, name, identification for DEM |
| DEM_projection | UTM | Universal Transverse Mercator |
| data_format | REAL*4 | DEM data format; valid formats are REAL*4 (4-byte floating point) and INTEGER*2 (2-byte, short integer) |
| DEM_hgt_offset | 0.00000 | Height offset in units |
| DEM_scale | 1.0 | Height scale used in DEM in meter/unit |
| width | 2000 | DEM width in pixels |
| nlines | 2000 | DEM number of lines |
| corner_north | 4095800.000 | Northing of first DEM pixel (m) |
| corner_east | 477300.000 | Easting of first DEM pixel (m) |
| post_north | -100.0000000 | DEM posting (pixel spacing) North direction; negative numbers indicate that DEM lines are listed from North to South |
| post_east | 100.0000000 | DEM posting (pixel spacing) East direction; negative numbers indicate that DEM |
In the case of EQA coordinates the last four lines are
replaced by:
| Keyword | Example | Definition |
| corner_lat | 37.0000000 | Latitude of first DEM pixel (decimal degrees) |
| corner_lon | -117.2500000 | Longitude of first DEM pixel (decimal degrees, values between -180 and 180) |
| post_lat | -8.3333000e-04 | DEM posting (pixel spacing) in latitude; negative numbers indicate that DEM pixels are listed from North to South |
| post_lon | 8.3333000e-04 | DEM posting (pixel spacing) in longitude; negative numbers indicate that DEM pixels are listed from East to West |
In the case of PS coordinates the following parameter is
added:
| Keyword | Example | Definition |
| PS_secant_lat | 71.0000000 | latitude of the secant plane with no distortion, +/-71 degrees for N. or S. hemispheres respectively |
Part 2: Ellipsoid Parameters
| Keyword | Example | Definition |
| ellipsoid_name: | Airy 1830 | Ellipsoid name (from list or specified by user) |
| ellipsoid_ra | 6377563.396 m | Ellipsoid semi-major axis in meter |
| ellipsoid_reciprocal_flattening | 299.3249646 | Ellipsoid reciprocal flattening (i.e. 1/f) |
Part 3: Datum Parameters
| Keyword | Example | Definition |
| datum_name: | United Kingdom National | Datum name (from list or specified by user) |
| datum_shift_dx | 370.300 m | Datum shift in x direction (Cartesian coordinates) relative to WGS84 |
| datum_shift_dy | -111.060 m | Datum shift in y direction (Cartesian coordinates) relative to WGS84 |
| datum_shift_dz | 431.170 m | Datum shift in z direction (Cartesian coordinates) relative to WGS84 |
| datum_scale_m | 0.00000e+00 | Datum shift scale m parameter, (1+datum_scale_m) is the scale factor |
| datum_rotation_alpha | 0.00000e+00 arc-sec | Datum rotation angle alpha (around x axis) in arc-seconds |
| datum_rotation_beta | 0.00000e+00 arc-sec | Datum rotation angle beta (around y axis) in arc-seconds |
| datum_rotation_gamma | 0.00000e+00 arc-sec | Datum rotation angle gamma (around z axis) in arc-seconds |
| datum_country_list | United Kingdom, England, Great Britain | Datum country list (included in datums.h list for parameter set selection |
Part 4: Projection Parameters for UTM, TM, OMCH, LCC,
PS, PC, AEAC coordinates
| Keyword | Example | Definition |
| projection_name | TM - United Kingdom, England | Projection name (from list or specified by user) |
| projection_zone | 0 | Zone number (0 in the case of one single zone) |
| false_easting | 400000.000 m | False Easting [m] |
| false_northing | -100000.000 m | False Northing [m] |
| projection_k0 | 0.9996013 | Scale factor k0 used by the projection |
| center_longitude | -2.0000000 decimal degrees | Center longitude in decimal degrees (-180...180) |
| center_latitude | 49.0000000 decimal degrees | Center latitude in decimal degrees (-90...90) |
In the case of SCH coordinates the following projection
parameters are used:
| Keyword | Example | Definition |
| SCH_peg_lat | SCH peg point latitude (degrees) | |
| SCH_peg_lon | SCH peg point longitude (degrees) | |
| SCH_heading | SCH heading (degrees) | |
| SCH_corner_s | SCH corner offset from peg point s (m) | |
| SCH_corner_c/TD> | SCH corner offset from peg point c (m) | |
| SCH_post_s | SCH posting along track s (m) | |
| SCH_post_c | SCH posting along track c (m) |
DESCRIPTION
DEM_par contains parameter values used by the Differential
Interferometry and Geocoding Software DIFF&GEO. The DEM_par
file contains information on a digital terrain model (DEM) or on
a map. The DEM_par file is generated using the program create_dem_par. The user is
interactively asked for the input used to describe a DEM or map.
A variety of projections are supported.
The formats used in DEM_par are defined in the in DIFF type definition file typedef_DIFF.h.
SEE ALSO
Users Guide, typedef_ISP.h, typedef_DIFF.h .
DIAGNOSTICS
All messages are generally self-explanatory.
NOTES
None.
© Copyrights for Documentation, Users Guide and Reference Manual by Gamma Remote Sensing, 2003.
UW, CW, TS, last change 20-Feb-2003.