QSWOT

A QGIS 3 plugin to discover, download, visualize, and analyze SWOT (Surface Water and Ocean Topography) hydrology data - river reaches and lakes - directly from NASA PO.DAAC's Hydrocron API.

Features

• Search by river or lake name - type "Rhine" or "Lake Michigan" and QSWOT resolves the matching SWORD reach IDs (rivers) or PLD lake IDs (lakes), then fetches their SWOT timeseries from Hydrocron.
• Streaming layer creation - features appear on the map as each reach / lake completes, so you see results building up instead of waiting for the whole batch to finish.
• Per-field selection - pick exactly which SWOT measurements you want (WSE, slope, width, area, discharge, etc.) via a tabbed checkbox UI.
• Auto layer styling - rivers as red linestrings, lakes as translucent blue polygons (with a separate point layer for sparse observations).
• Statistics dialog - compute Pearson / Spearman / Kendall correlations between any two numeric fields, or plot a time series of one field over time, with built-in mouse-wheel zoom and matplotlib navigation tools.
• Country-wide zoom - first features auto-fit the canvas to a regional overview so you see where the data is.
• Cancellable - every fetch runs as a non-blocking QGIS task with a Cancel button; closing QGIS mid-fetch shuts down cleanly.

Requirements

• QGIS 3.0 or newer.
• Python packages: numpy, matplotlib, and scipy.
  • numpy and matplotlib ship with every standard QGIS distribution (Windows OSGeo4W, official macOS package, most Linux QGIS builds).
  • scipy is optional: it's needed for Spearman and Kendall correlations. Without it, only Pearson is available. If you need Spearman/Kendall and don't have scipy, install it into the QGIS Python environment:
    • Windows (OSGeo4W shell): pip install scipy
    • macOS (official QGIS): /Applications/QGIS.app/Contents/MacOS/bin/pip3 install scipy
    • Linux: pip3 install --user scipy
• Network access to:
  • https://soto.podaac.earthdatacloud.nasa.gov (Hydrocron timeseries)
  • https://fts.podaac.earthdata.nasa.gov (river reach ID lookup)
  • https://lakes.swot-lake.workers.dev (lake ID lookup)
  • Proxy / SSL settings configured in QGIS (Settings → Options → Network) are honored automatically.

Geographic / data restrictions

• SWOT is a global mission, but only locations sampled by the satellite (i.e., not consistently every point) have data. Coverage varies by latitude and orbit phase.
• Hydrocron returns data starting from the SWOT operational era (late 2022 onwards). Date ranges before that will return empty results.
• Some river reaches and lakes (especially very small ones) may have only a handful of observations per year due to SWOT's ~21-day repeat cycle.

Installation

From the QGIS Plugins repository (recommended once published)

1. In QGIS: Plugins → Manage and Install Plugins.
2. Search for QSWOT and click Install.

From source (development)

1. Clone or download this repository.
2. Copy or symlink the swot/ folder into your QGIS plugins directory:
   • Windows: %APPDATA%\QGIS\QGIS3\profiles\default\python\plugins\
   • macOS: ~/Library/Application Support/QGIS/QGIS3/profiles/default/python/plugins/
   • Linux: ~/.local/share/QGIS/QGIS3/profiles/default/python/plugins/
3. Restart QGIS and enable the plugin via Plugins → Manage and Install Plugins.

Usage

1. Launch QSWOT from the toolbar icon or Web → &QSWOT.
2. In the dialog:
   • Enter a river name (e.g. Rhine) and/or a lake name (e.g. Constance).
   • Pick a date range.
   • Open the Query Attributes tabs and check the fields you want returned for each feature type.
   • Optionally cap the number of reaches/lakes fetched.
3. Click OK. Reaches stream into a red linestring layer; lakes into a blue polygon layer (and a point layer when SWOT has only point observations for some lakes).
4. Click River Statistic or Lake Statistic to open the stats dialog, where you can plot time series or compute correlations.
5. Lake stats require a selection first - lake searches can return features from many physically distinct lakes (e.g. "caspian" returns Caspian Sea and Caspian Lake); select the rows for the lake of interest in the attribute table before opening the stats dialog.

Issues and contributions

• Report bugs: https://github.com/0xNima/QSWOT/issues
• Source code: https://github.com/0xNima/QSWOT

License

QSWOT is released under the GNU General Public License v3.0 or later (GPL-3.0-or-later). See LICENSE for the full text.

Acknowledgements

• The SWOT mission is a joint program of NASA and CNES (Centre National d'Études Spatiales).
• Data and APIs courtesy of NASA JPL PO.DAAC.