GeoExpress Command Line Utilities: A Complete Quick-Start GuideGeoExpress is a high-performance image compression and tiling tool widely used in GIS, remote sensing, and mapping workflows to reduce storage and speed delivery of large raster datasets. Its command-line utilities let you automate compression, convert formats, generate image pyramids, and prepare imagery for web and enterprise use. This guide walks through installation, core commands, common workflows, scripting tips, and troubleshooting to get you productive quickly.
What GeoExpress command-line utilities are for
GeoExpress command-line tools provide batchable, script-friendly access to the core functionality of the GeoExpress GUI:
- Compress large rasters to fast, space-efficient formats for archival, distribution, or optimized serving.
- Create multiresolution pyramids (overviews) so viewers and servers can request appropriate zoom levels.
- Tile and reproject imagery to match target coordinate systems or web mapping tiling schemes.
- Extract metadata and validate files for integration into catalogues and processing pipelines.
Installation and prerequisites
- Obtain GeoExpress from the vendor (make sure you have a valid license).
- Supported OS: Windows and Linux (check your version compatibility).
- Prerequisites: typical libraries and system requirements specified by the vendor; ensure you have command-line access and PATH configured so GeoExpress executables are reachable from terminals or scripts.
Common command-line utilities and their purposes
Note: exact executable names and flags depend on GeoExpress versions; consult your local installation’s help output (e.g., –help) for precise syntax.
- gxcompress / geocompress: Compress imagery into GeoExpress’s optimized formats. Use when you need efficient storage and fast decompression.
- gxreformat / georeformat: Convert between raster formats (GeoTIFF, MrSID, JPEG2000, etc.).
- gxbuildoverviews / geobuild: Generate image pyramids (multiresolution overviews).
- gxtile / geotile: Create tiles (fixed-size or tilesets) for web mapping or tile caches.
- gxinfo / geoinfo: Inspect metadata, geometry, and internal structure of compressed files.
- gxvalidate / geovalidate: Verify file integrity and report issues.
Basic workflow examples
Below are generalized workflows; adapt flags and filenames to your installed version.
- Compress a GeoTIFF to GeoExpress format
- Purpose: reduce storage while preserving required quality.
- Typical steps:
- Inspect source with gxinfo.
- Choose compression options (lossy/lossless, quality, block size).
- Run gxcompress with band selection, compression level, and output path.
Example (conceptual):
gxinfo source.tif gxcompress -input source.tif -output source.gx -quality 90 -tile 1024 - Build pyramids (overviews)
- Purpose: accelerate zoomed display and reduce I/O.
gxbuildoverviews -input source.gx -levels 2,4,8,16
- Tile imagery for web delivery
- Purpose: produce XYZ/WMTS-style tiles or a tileset for a server.
gxtile -input source.gx -scheme XYZ -tileSize 256 -zoomMin 0 -zoomMax 14 -output tiles/
- Reformat and reproject
gxreformat -input source.tif -output source.jp2 -srs EPSG:3857
Scripting and automation tips
- Use shell scripts (bash on Linux/macOS, PowerShell on Windows) to chain commands: inspect -> compress -> build overviews -> tile -> validate.
- Add logging and exit-code checks to catch failures in pipelines.
- Process large collections with parallelism tools (GNU parallel, xargs -P) but be mindful of I/O and license concurrency limits.
- Store chosen compression profiles as reusable parameter sets or wrapper scripts.
Choosing compression settings
- Lossless vs lossy: choose lossless for analytical datasets (DEM, multispectral with analysis needs) and lossy for imagery where visual fidelity is primary but storage matters.
- Quality parameter: test at multiple settings on representative samples and compare filesize, visual quality, and downstream processing results.
- Tile/block size: align tile size with typical viewer request sizes (256–2048 px). Larger tiles can improve throughput for large reads but increase memory use.
Integrating with GIS servers and viewers
- Many web servers and tile caches accept tiled outputs (XYZ, MBTiles, WMTS). Produce the matching tile layout and metadata (tilemapresource.xml, tilejson).
- When serving compressed tiles directly, ensure the server supports your compressed format or convert to an accepted delivery format on-the-fly.
Troubleshooting common issues
- Command not found: ensure the GeoExpress executables folder is on PATH.
- Performance bottlenecks: check disk I/O and CPU; increase parallel jobs carefully; use local SSD for temporary processing.
- Unexpected visual artifacts: try higher quality or lossless compression; verify band order and color profile handling.
- License errors: verify license server availability and concurrency limits.
Example end-to-end script (conceptual)
A typical pipeline for a folder of GeoTIFFs:
- Loop over files
- Compress to .gx
- Build overviews
- Tile to XYZ
- Validate outputs
(Replace with exact command names/flags for your version and OS.)
Best practices checklist
- Test settings on representative samples before batch processing.
- Keep source files unchanged; write outputs to a separate folder.
- Automate metadata capture (date, EPSG, compression used) for provenance.
- Monitor disk and memory when processing huge datasets.
- Maintain small test datasets for regression testing when updating GeoExpress versions.
Further reading and help
- Use the command-line help (e.g., gxcompress –help) for exact flag names and options.
- Consult vendor documentation and release notes for features and compatibility.
- For scripting patterns, search community forums for examples matching your OS and dataset types.
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