NASADEM 2.1.0

Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) search and download utility

NASADEM - Digital Elevation Model (DEM) Access Utility

This Python package provides utilities for accessing and downloading Digital Elevation Model (DEM) data from the NASADEM dataset, which is a reprocessed version of the Shuttle Radar Topography Mission (SRTM) data.

Version 2.0.0 modernizes the package to use NASA's official earthaccess library for reliable and efficient data access from NASA's Earthdata Cloud.

Gregory H. Halverson (they/them)
[e-mail]
NASA Jet Propulsion Laboratory 329G

What's New in v2.0.0

• 🚀 Modern Data Access: Uses NASA's official earthaccess package
• ✅ Reliable Downloads: Built-in retry logic and error handling
• ☁️ Cloud-Optimized: Direct access to NASA Earthdata Cloud
• 🔐 Simplified Authentication: Multiple authentication options (.netrc, environment variables, interactive)
• 🗑️ Removed Legacy Code: Deprecated old LP DAAC connection methods

Installation

pip install NASADEM

Or install from source:

git clone https://github.com/gregory-halverson/NASADEM.git
cd NASADEM
pip install -e .

Prerequisites

You need a NASA Earthdata account to download NASADEM data.

Authentication

There are several ways to authenticate:

Option 1: Interactive Login (Recommended for first-time users)

import earthaccess
earthaccess.login()  # Will prompt for credentials and optionally save them

Option 2: .netrc File

Create a ~/.netrc file with your credentials:

machine urs.earthdata.nasa.gov
    login YOUR_USERNAME
    password YOUR_PASSWORD

Then set proper permissions:

chmod 600 ~/.netrc

Option 3: Environment Variables

export EARTHDATA_USERNAME=your_username
export EARTHDATA_PASSWORD=your_password

Option 4: Direct Credentials

from NASADEM import NASADEMConnection

nasadem = NASADEMConnection(
    username="your_username",
    password="your_password",
    persist_credentials=True  # Optionally save to .netrc
)

Usage

Basic Usage with Default Instance

from NASADEM import NASADEM
from rasters import RasterGrid

# Define target area
geometry = RasterGrid.from_bbox(
    xmin=-118.5, ymin=33.5, xmax=-117.5, ymax=34.5,
    cell_size=30, crs="EPSG:4326"
)

# Get elevation data
elevation = NASADEM.elevation_m(geometry)
print(f"Elevation range: {elevation.min():.1f} to {elevation.max():.1f} meters")

# Get surface water body mask
water = NASADEM.swb(geometry)

Custom Connection

from NASADEM import NASADEMConnection

# Create connection with custom download directory
nasadem = NASADEMConnection(
    download_directory="~/my_nasadem_data"
)

# Use it the same way
elevation = nasadem.elevation_m(geometry)

Point Extraction

from rasters import Point, MultiPoint
from NASADEM import NASADEM

# Single point
point = Point(-118.0, 34.0)
elevation = NASADEM.elevation_m(point)
print(f"Elevation at point: {elevation:.1f} m")

# Multiple points
points = MultiPoint([
    Point(-118.0, 34.0),
    Point(-117.5, 33.8),
    Point(-118.2, 34.2)
])
elevations = NASADEM.elevation_m(points)
print(f"Elevations: {elevations}")

Working with Tiles

from NASADEM import NASADEM

# Get tiles covering an area
tiles = NASADEM.tiles(geometry)
print(f"Tiles needed: {tiles}")

# Download a specific tile
granule = NASADEM.download_tile("n34w118")
elevation = granule.elevation_m
swb = granule.swb

API Reference

NASADEMConnection

Main class for accessing NASADEM data.

Methods:

• elevation_m(geometry): Get elevation in meters
• elevation_km(geometry): Get elevation in kilometers
• swb(geometry): Get surface water body mask
• download_tile(tile): Download a specific tile
• tiles(geometry): Get list of tiles covering a geometry

Parameters:

• username (str, optional): NASA Earthdata username
• password (str, optional): NASA Earthdata password
• working_directory (str, optional): Working directory for temporary files
• download_directory (str, optional): Directory for downloaded tiles (default: ~/data/NASADEM)
• persist_credentials (bool, optional): Save credentials to .netrc (default: False)
• skip_auth (bool, optional): Skip authentication (useful for testing, default: False)

NASADEMGranule

Represents a single NASADEM tile.

Properties:

• elevation_m: Elevation raster in meters
• swb: Surface water body mask
• geometry: Raster geometry of the tile
• tile: Tile identifier (e.g., "n34w118")

Data Description

NASADEM provides:

• Elevation data: 1 arc-second (~30m) resolution global coverage (60°N to 56°S)
• Surface water body mask: Boolean mask of water bodies
• Void-filled: Improved version of SRTM with fewer data voids
• Accuracy: Vertical accuracy typically better than 16m (absolute), 10m (relative)

Tile Naming Convention

Tiles are named using latitude/longitude: {n|s}XX{e|w}XXX

Examples:

• n34w118: 34°N to 35°N, 118°W to 117°W (Los Angeles area)
• s10e142: 10°S to 9°S, 142°E to 143°E (Northern Australia)

Migration from v1.x

If you're upgrading from v1.x:

1. Authentication: Update to use earthaccess authentication methods
2. No more URL construction: The package now handles data discovery automatically
3. Deprecated: LPDAACDataPool class is no longer used
4. Same API: The main elevation_m(), elevation_km(), and swb() methods work the same

Old code (v1.x):

from NASADEM import NASADEMConnection

nasadem = NASADEMConnection(
    username="user",
    password="pass",
    remote="https://e4ftl01.cr.usgs.gov"  # Old URL
)

New code (v2.0):

from NASADEM import NASADEMConnection

# Simpler - earthaccess handles the URLs
nasadem = NASADEMConnection(
    username="user",
    password="pass"
)

Troubleshooting

Authentication Issues

If you get authentication errors:

import earthaccess
earthaccess.login(persist=True)  # Save credentials

Download Failures

The package automatically retries failed downloads. If problems persist:

• Check your internet connection
• Verify your NASA Earthdata credentials
• Check NASA Earthdata system status: https://status.earthdata.nasa.gov/

Tile Not Available

Some areas may not be covered by NASADEM (latitudes > 60°N or < 56°S). The error message will indicate this.

References

• NASA JPL. (2013). Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM). NASA Earthdata. Retrieved from https://earthdata.nasa.gov.
• Farr, T. G., Rosen, P. A., Caro, E., Crippen, R., Duren, R., Hensley, S., ... & Alsdorf, D. (2007). The Shuttle Radar Topography Mission. Reviews of Geophysics, 45(2), RG2004. https://doi.org/10.1029/2005RG000183
• NASADEM Data Product. (2020). NASA Jet Propulsion Laboratory. Retrieved from https://doi.org/10.5067/MEaSUREs/NASADEM/NASADEM_HGT.001
• earthaccess Documentation. Retrieved from https://earthaccess.readthedocs.io/

License

See LICENSE file.

Documentation

• Migration Guide - How to upgrade from v1.x to v2.0.0
• Changelog - Version history and changes
• Release Summary - Detailed v2.0.0 release notes

Contributing

Issues and pull requests are welcome at https://github.com/gregory-halverson/NASADEM