topo-assembly v3.2.3

Mercurial revision 5786:5c8b45563631 | 2026-08-04

Description

topo-assembly assembles tiles of data (e.g., SRTM) into a single output. It creates:

  • A .nc (NetCDF) file.

  • A .grd (GRD format) file (optional).

The tiling description is provided in an input file that defines the arrangement of the tiles. See Tiling Description Format.

Usage

topo-assembly [OPTIONS] input

Options

General Options

Option

Description

-h, --help

Display help and exit.

--debug

Enable debug verbose mode.

Input Options

Option

Description

--litto3D <file>

Path to an IGN.asc file to assemble with topography. Multiple calls allowed.

--litto3D-list <file>

Path to an ASCII file containing a list of IGN.asc files to assemble.

-mask <value>

Specify the masked value (default: +INFINITY).

--allow-missing

Continue assembly even if some tiles are missing in the frame.

Projection and Grid Options

Option

Description

--cartesian <grid>

Cartesian grid settings in the format [xmin:dx:xmax;ymin:dy:ymax]. Useful for handling poorly geo-referenced rasters.

--proj=<proj4_string>

PROJ4 option string to convert Cartesian coordinates to spherical.

Output Options

Option

Description

-o <rootname>

Root name for output files (default: assembly).

-grd

Also save topography in GRD format (in addition to NetCDF).

-deflate <level>

Compression level for output files (0 to 9). Default: 0 (no compression).

-short

Enable reading of short integer format for input data.

-shrinked

Shrink the topography to the minimum frame defined by the topography.

Tiling Description Format

The input file must follow this format:

  1. First line: Contains the X (#columns) and Y (#rows) size of the output, in number of tiles. Example: 3 2

  2. Subsequent lines: Each line describes a tile with:

    • X (column index) and Y (row index) of the tile position (origin is bottom/left).

    • File name of the tile.

    • Variable name of the data in the file.

Example:

3 2
0 0 n03_e008_3arc_v1.nc Band1
1 0 n03_e009_3arc_v1.nc Band1
2 0 n03_e010_3arc_v1.nc Band1
0 1 n04_e008_3arc_v1.nc Band1
1 1 n04_e009_3arc_v1.nc Band1
2 1 n04_e010_3arc_v1.nc Band1

Examples

Basic Assembly

Assemble tiles described in tiling.txt:

topo-assembly tiling.txt

Custom Output Name

Assemble tiles and save outputs with a custom root name:

topo-assembly -o my_output tiling.txt

Enable GRD Output

Assemble tiles and save in both NetCDF and GRD formats:

topo-assembly -grd tiling.txt

Compress Output

Assemble tiles with compression level 5:

topo-assembly -deflate 5 tiling.txt

Use Short Integer Format

Assemble tiles with short integer input data:

topo-assembly -short tiling.txt

Shrink to Minimum Frame

Shrink the output to the minimum frame defined by the topography:

topo-assembly -shrinked tiling.txt

Allow Missing Tiles

Continue assembly even if some tiles are missing:

topo-assembly --allow-missing tiling.txt

Cartesian Grid

Assemble tiles with a Cartesian grid:

topo-assembly --cartesian "[0:1:100;0:1:100]" tiling.txt

PROJ4 Projection

Convert Cartesian coordinates to spherical using a PROJ4 string:

topo-assembly --proj="+proj=utm +zone=10 +ellps=WGS84" tiling.txt

LITTO3D Assembly

Assemble LITTO3D files (IGN.asc format):

topo-assembly --litto3D LITTO3D_FRA_0374_6414_MNT5_20250531_LAMB93_RGF93_IGN69.asc tiling.txt

Assemble multiple LITTO3D files:

topo-assembly \
  --litto3D file1.asc \
  --litto3D file2.asc \
  tiling.txt

Assemble LITTO3D files from a list:

topo-assembly --litto3D-list litto3d_files.txt tiling.txt

Combined Options

Assemble tiles with compression, GRD output, and a custom root name:

topo-assembly -o my_topography -grd -deflate 4 tiling.txt

Environment Variables

topo-assembly does not rely on specific environment variables. However, if PROJ4 is used, ensure the proj library is correctly installed and configured on your system.

Notes

  1. Input Files:

    • The input file must follow the Tiling Description Format.

    • Supported input formats include NetCDF and IGN.asc (for LITTO3D).

  2. Output Files:

    • By default, outputs are named assembly.nc and assembly.grd (if -grd is used).

    • Use -o to specify a custom root name.

  3. Mask Handling:

    • Use -mask to define a custom masked value (default: +INFINITY).

    • Masked values are excluded from the assembly process.

  4. Performance:

    • For large datasets, consider using -deflate to reduce file size.

    • The -shrinked option can reduce memory usage by limiting the output to the minimum frame.

  5. Debugging:

    • Use --debug to enable verbose output for troubleshooting.

See Also