Transformez

Global vertical datum transformations, simplified.

Transformez is a standalone Python engine for converting geospatial data between vertical datums (e.g., MLLW ↔ NAVD88 ↔ Ellipsoid).

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(Above: A generated vertical shift grid transforming MLLW to NAVD88)

transformez run -R loc:"new orleans" -E 3s -I mllw -O 5703

Installation

Prerequisites: HTDP

Transformez relies on the NGS Horizontal Time-Dependent Positioning (HTDP) software to perform highly accurate plate tectonic and frame transformations. You must install this separately.

For Windows:

1. Download the pre-compiled executable (htdp.exe) directly from the NOAA HTDP page.
2. Place htdp.exe in a directory that is in your system's PATH (e.g., C:\Windows\System32 or a custom scripts folder).

For Linux / macOS:

You will need a Fortran compiler (like gfortran) to compile the source code.

# 1. Download the Fortran source code
wget https://geodesy.noaa.gov/TOOLS/Htdp/HTDP-download.zip
unzip HTDP-download.zip

# 2. Compile it
gfortran -o htdp htdp.f

# 3. Move it to your PATH
sudo mv htdp /usr/local/bin/

Install Transformez

Once HTDP is accessible in your terminal, install the python package:

pip install transformez

Usage

Generate a vertical shift grid for anywhere on Earth.

# Transform MLLW to WGS84 Ellipsoid in Norton Sound, AK

transformez run -R -166/-164/63/64 -E 1s -I mllw -O 4979

Transform a raster directly. Transformez reads the bounds/resolution from the file.

transformez run my_dem.tif -I mllw -O 5703

Integrate directly into your download pipeline.

# Download GEBCO and shift EGM96 to WGS84 on the fly
fetchez gebco ... --hook transformez:datum_in=5773,datum_out=4979

Python API

Transformez provides a high-level API for embedding transformations directly into your Python scripts, Jupyter Notebooks, or automated pipelines.

import transformez

# ---------------------------------------------------------
# Generate a Shift Grid
# ---------------------------------------------------------
# Returns a 2D numpy array. Optionally saves to a file.
# Requesting "mllw" in India triggers the Global Fallback (FES2014) automatically.

shift_array = transformez.generate_grid(
    region=[80, 85, 10, 15],  # [West, East, South, North]
    increment="3s",           # Grid resolution
    datum_in="mllw",
    datum_out="4979",         # WGS84 Ellipsoid
    out_fn="india_shift.tif"  # Optional: Save to disk
)

# ---------------------------------------------------------
# Transform an Existing Raster
# ---------------------------------------------------------
# Applies the datum shift directly to a DEM and saves the result.

out_file = transformez.transform_raster(
    input_raster="my_dem_mllw.tif",
    datum_in="mllw",
    datum_out="5703:g2012b",  # NAVD88 using specific GEOID12B
    output_raster="my_dem_navd88.tif"
)

Supported Datums

🌊 Supported Tidal Surfaces:

EPSG	NAME	DESC
1089	mllw	[USA]
5866	mllw	[USA]
1091	mlw	[USA]
5869	mhhw	[USA]
5868	mhw	[USA]
5714	msl	[USA]
5713	mtl	[USA]
0	crd	[USA]
5609	IGLD85	[USA]
9000	LWD_IGLD85	[USA]
5702	NGVD29	[GLOBAL]
9001	lat	[GLOBAL]
9002	hat	[GLOBAL]
9003	mss	[GLOBAL]

🌐 Ellipsoidal / Frame Datums (EPSG):

EPSG	NAME	DESC
4979	WGS84	World Geodetic System 1984
6319	NAD83	North American Datum 1983

🏔️ Orthometric / Geoid-Based (EPSG):

EPSG	NAME	DESC
5703	NAVD88 height	(Default Geoid: g2018)
6360	NAVD88 height (usFt)	(Default Geoid: g2018)
8228	NAVD88 height (Ft)	(Default Geoid: g2018)
6641	PRVD02 height	(Default Geoid: g2018)
6642	VIVD09 height	(Default Geoid: g2018)
6647	CGVD2013(CGG2013)	(Default Geoid: CGG2013)
3855	EGM2008 height	(Default Geoid: egm2008)
5773	EGM96 height	(Default Geoid: egm96)

🌍 Available Geoids:

g2018, g2012b, geoid09, xgeoid20b, xgeoid19b, egm2008, egm96, CGG2013

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