fetchez-transformez

The Vertical Transformation Extension for Fetchez.

⚠️ BETA STATUS: This project is in active development.

Transformez provides robust vertical datum transformations for geospatial data. It acts as a bridge between the messy reality of vertical datums (Tidal, Orthometric, Ellipsoidal) and your data processing pipeline.

It works in two modes:

1. Standalone CLI: Generate shift grids (GTX) for any region.
2. Fetchez Plugin: Automatically transform data as it is downloaded.

🌎 Features

• Tidal Transformations: Wraps NOAA's VDatum to transform between tidal surfaces (MLLW, MHHW) and geometric datums.
• Geoid Grids: Seamlessly applies PROJ-CDN geoids (GEOID18, GEOID12B, EGM2008).
• Time-Dependent Shifts: Integrates HTDP to handle crustal velocities and epoch transformations (e.g., ITRF2014 @ 2020.0 -> NAD83(2011) @ 2010.0).
• Grid Engine: Automates the fetching, stitching, and mosaicking of partial VDatum grids into a single continuous shift surface.

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📦 Installation

Requires Fetchez (v0.3.3+) and standard geospatial libs.

# Clone and install
git clone [https://github.com/ciresdem/fetchez-transformez.git](https://github.com/ciresdem/fetchez-transformez.git)
cd fetchez-transformez
pip install -e .

Note: For Tidal transformations, you must have Java installed to run the embedded VDatum JAR.

🛠 Usage

1. As a Fetchez Hook (The Pipeline Way) Automatically transform data immediately after download. This generates a shift grid for the exact region of the downloaded data and applies it.

# Download SRTM and convert from EGM96 (Default) to Ellipsoidal (WGS84)
fetchez srtm -R -120/-119/33/34 --hook transformez:in=5773,out=4979

# Download Multibeam and convert from MLLW to NAD83(2011) Ellipsoidal
fetchez multibeam -R ... --hook transformez:in=5866,out=6319

2. As a Standalone CLI Use transformez to generate shift grids for use in other software (like PDAL, GDAL, or CARIS).

# Generate a GTX shift grid from MLLW to NAVD88
transformez -R -95/-94/28/29 -E 1s \
    --vdatum-in "5866" \
    --vdatum-out "6319:g2012b" \
    --output mllw_to_navd88.gtx

🗺 Supported Datums

Transformez supports a "Compound Datum" string format: EPSG:GEOID.

• Ellipsoidal: 6319 (NAD83 2011), 4979 (WGS84)

• Orthometric: 5703 (NAVD88), 5702 (NGVD29)

• Tidal: 5866 (MLLW), 5869 (MHHW), 5714 (MSL)

• Geoids: g2018, g2012b, xgeoid20b

Example: 6319:g2018 represents NAD83(2011) Orthometric height derived via Geoid18.

📄 License

MIT