TL;DR: Off-Nadir Delta is a browser-based WebGIS platform for satellite imagery analysis. Access Sentinel-1 SAR, Sentinel-2 optical, VIIRS nighttime lights, and NASA FIRMS active fire data — no GIS software required. Free tier available. Created by Kazushi Motomura (Off-Nadir Lab), an independent personal project.
Off-Nadir Delta WebGIS
Off-Nadir Delta is a web-based satellite imagery workspace for anyone who is curious about satellite data — especially if you have never used it before and just want to see your area from space in a clear, simple way.
From there, you can slowly discover what is possible: quickly check a location after an event, watch how places change over time, and build maps you can share with others — all in your browser, without GIS software.
Get Started Without GIS Skills
Open the map in your browser, choose a place you care about, and see satellite imagery in seconds. No prior experience or special tools required.
Learn by Exploring
Try different views and dates to understand what you are seeing. Notice how water, vegetation, and cities appear in satellite images just by looking and comparing.
Speed Up Your Daily Checks
If you already work with satellite data, use Off-Nadir Delta to do quick visual checks and change detection before you dive into heavier tools and scripts.
Create a free account to explore your own locations and gently learn how satellite imagery can support your work and ideas.
Why Off-Nadir Delta?
Supported Satellite Data
Sentinel-1 (SAR)
Synthetic Aperture Radar imagery that works day and night, through clouds and smoke. Ideal for flood mapping, disaster response, and all-weather monitoring.
- • Ground Range Detected (GRD)
- • Radiometric Terrain Corrected (RTC)
- • Resolution: ~10-20 meters
- • Revisit: 6 days
Sentinel-2 (Optical)
Multispectral optical imagery with 13 spectral bands. Perfect for vegetation analysis, land cover mapping, and environmental monitoring.
- • Level-2A (atmospherically corrected)
- • Resolution: 10 meters (visible/NIR)
- • Revisit: 5 days
- • 13 spectral bands
VIIRS Nighttime Lights (NASA Black Marble)
Day-Night Band (DNB) imagery showing nighttime artificial lights from space. Ideal for urban analysis, economic activity monitoring, and disaster impact assessment.
- • VNP46A2 Gap-Filled BRDF-Corrected NTL
- • Resolution: ~500 meters
- • Daily composite products
- • Cloud-free nighttime observations
NASA FIRMS Active Fire
Near real-time active fire hotspot data from NASA FIRMS (Fire Information for Resource Management System). No API key or tokens required.
- • VIIRS (S-NPP, NOAA-20, NOAA-21): 375m resolution
- • MODIS (Terra, Aqua): 1km resolution
- • Updated daily via NASA GIBS WMS
- • Free access, no token cost
Technology Stack
Map Visualization
Data Discovery
Cloud Optimized GeoTIFF
Web Framework
Built with modern geospatial standards: SpatioTemporal Asset Catalog (STAC) for data discovery and Cloud Optimized GeoTIFF (COG) for efficient streaming of satellite imagery.
Data Sources
Off-Nadir Delta provides access to satellite data from trusted, authoritative sources:
Copernicus Programme (ESA)
European Space Agency's Earth observation programme providing free and open Sentinel satellite data.
AWS Earth Search
Amazon Web Services hosting of Sentinel-2 data for fast, reliable access.
Microsoft Planetary Computer
Sentinel-1 RTC data processed and hosted by Microsoft for radiometrically corrected SAR imagery.
NASA GIBS / FIRMS
NASA Global Imagery Browse Services (GIBS) and Fire Information for Resource Management System (FIRMS) for active fire hotspot and nighttime lights data.
Open Data Policy
All Sentinel data is freely available under the Copernicus open data policy. NASA data (VIIRS, FIRMS) is provided under NASA's open data policy for non-commercial and commercial use.
Data Accuracy & Disclaimer
Off-Nadir Delta provides access to publicly available satellite imagery on a best-effort basis. The platform streams data directly from authoritative sources (ESA Copernicus, NASA, AWS, Microsoft Planetary Computer) and does not modify or reprocess the original data.
Limitations to be aware of:
- Satellite imagery may contain cloud cover, atmospheric artifacts, or sensor noise that can affect visual interpretation.
- Data availability depends on upstream providers; coverage gaps or delays may occur without notice.
- Active fire data (NASA FIRMS) has a latency of approximately 3 hours (VIIRS) to 1-2 days (MODIS) and should not be used as the sole source for emergency decisions.
- NDVI and other derived indices are computed from source bands and may differ from values produced by specialized processing pipelines.
- This platform is independently developed and is not affiliated with ESA, NASA, or any data provider.
For critical applications (disaster response, legal evidence, regulatory compliance), always verify satellite observations with authoritative ground-truth sources. See our Terms of Service and Privacy Policy for full details.