README.md

Transformez

Global vertical datum transformations, simplified.

Transformez builds and applies vertical transformations across geodetic, tidal, and model-based height references, from local datums to global surfaces.

Transformez resolves your input and output references, computes the optimal geodetic pathway on the fly, and generates spatially varying shift grids. Where regional models end, Transformez continues across open ocean and inland using global proxies, coastal blending, and meter-based inland decay.

Transformez is part of the Continuous DEMs Project, an ecosystem of tools for modern, continuous digital elevation model generation. Originally incubated within CUDEM, the engine has evolved into a standalone datum transformation suite.

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📦 Installation

Install the Transformez Python package:

pip install transformez

# Install the external geodetic engines through the CLI (HTDP is only needed for dynamic-frame and epoch transformations):
transformez htdp install
transformez vdatum install   # optional, for direct VDatum comparison/validation

🚀 Quickstart

Generate a vertical shift grid anywhere on Earth.

# Transform MLLW to WGS84 ellipsoidal height in Norton Sound, AK
transformez build -R -166/-164/63/64 -E 1s -I vdatum:mllw -O epsg:4979

# Transform a raster directly. Transformez reads the bounds and resolution from the file.
transformez shift my_dem.tif -I vdatum:mllw -O epsg:5703

# Inspect a reference or plan a transformation before running it.
transformez info reference vdatum:mllw
transformez plan -I vdatum:mllw -O epsg:5703 -R -166/-164/63/64

From Python:

import transformez

shift_array = transformez.generate_grid(
    region=[80, 85, 10, 15],   # [West, East, South, North]
    increment="3s",
    datum_in="vdatum:mllw",
    datum_out="epsg:4979",
)

⚠️ Shift grids are always added to your elevation data; the sign conventions are handled internally. See the methodology guide for the physical intuition.

📚 Documentation

Would you like to know more? Check out the Official Documentation to learn about:

• The Python API: Build, inspect, reproject, and apply vertical transformations directly in your applications.
• Offline Field Ops: Pre-fetch global FES models, VDatum grids, and NASA coastlines for offline execution (transformez prefetch).
• Data Provenance: Learn how Transformez embeds automated metadata tags into output GeoTIFFs for strict scientific traceability.
• Validation & Accuracy: Measured agreement against NOAA CO-OPS, NOAA VDatum, FES/DTU, and NGS HTDP.
• Integrations: Use Transformez directly from Fetchez workflows or through the QGIS plugin.

⚖ License

This project is licensed under the MIT License - see the LICENSE file for details.

Copyright (c) 2010-2026 Regents of the University of Colorado