dem-handler

Utility package for handling various Digital Elevation Models (DEMs). The package enables access to data stored in cloud as well as local copies of dem datasets.

Functionality

The core functionality of this package is to provide mosaicked DEMs for arbitrary bounds. This is valuable for creating a mosaicked DEM that covers a scene. The package provides high level functions for supported DEMs, and low level functions that can be used to handle custom DEMs.

The DEM mosaicking functions have the following features:

• When requesting a DEM for bounds that include the ocean, the mosaicked DEM will include the ocean, setting the value of non-land pixels to 0 (height above the geoid).
• If a geoid height model is provided, the height above the ellipsoid can be returned.
• The functions work for DEM tiles stored in the cloud or locally.
• The mosaicked DEM can be returned in memory, as well as saved to a file for reuse.
• When a DEM has different resolutions, the mosaicked DEM will be returned with the highest resolution.
• If the DEM is requested over the antimeridian, the request will be split into Eastern and Western hemisphere components, then merged back together in an appropriate local coordinate reference system.

For more information on how the above functionality was implemented, see the design documentation.

Supported DEMS

• Copernicus Global 30m (cop_glo30)
• REMA (2m,10m, ...)

Usage

Create mosaicked DEM for bounds from cloud files

import os
from dem_handler.dem.cop_glo30 import get_cop30_dem_for_bounds
from dem_handler.dem.rema import get_rema_dem_for_bounds

import logging
logging.basicConfig(level=logging.INFO)

# Set the bounds and make a directory for the files to download

bounds = (72,-70, 73, -69)
save_dir = 'TMP'
os.makedirs(save_dir, exist_ok=True)

# Copernicus Global 30m DEM 

get_cop30_dem_for_bounds(
    bounds = bounds,
    save_path = f'{save_dir}/cop_glo30.tif',
    adjust_at_high_lat=False,
    cop30_folder_path = save_dir,
    ellipsoid_heights = False,
    download_dem_tiles = True
)

# REMA DEM (32m)

get_rema_dem_for_bounds(
    bounds=bounds,
    save_path=f'{save_dir}/rema.tif',
    resolution=32,
    bounds_src_crs=4326,
)

Create mosaicked DEM using an existing filesystem

import os
from dem_handler.dem.cop_glo30 import get_cop30_dem_for_bounds

import logging
logging.basicConfig(level=logging.INFO)

# The NCI - copernicus Global 30m DEM 

bounds = (72,-70, 73, -69)
save_dir = 'TMP'
os.makedirs(save_dir, exist_ok=True)

# Set paths for existing files / folders
GEOID_PATH = "/g/data/yp75/projects/ancillary/geoid/us_nga_egm2008_1_4326__agisoft.tif"

COP30_FOLDER_PATH = "/g/data/v10/eoancillarydata-2/elevation/copernicus_30m_world/"

get_cop30_dem_for_bounds(
    bounds = bounds,
    save_path = f'{save_dir}/cop_glo30.tif',
    ellipsoid_heights = True,
    adjust_at_high_lat = True,
    cop30_folder_path = COP30_FOLDER_PATH,
    geoid_tif_path = GEOID_PATH,
    download_dem_tiles = False,
    download_geoid = False,
)

Install

Currently, we only support installing dem-handler from source.

1. Clone the repository
2. Install using conda (environment.yaml) or pixi (pyproject.toml)

Both will install the package locally in editable mode.

Developer Setup

This repository uses pixi to manage the environment through the pyproject.toml file.

See the developer guide document for set-up instructions.