Reference

Satellite Data Sources

Every data source behind the Map, the Watchfloor, and Delta Agent — what it is, how sharp it is, how often it refreshes, and how to credit it. All open data, all in your browser.

TL;DR: Off-Nadir Delta provides Sentinel-2 optical (10 m, 13 bands), Sentinel-1 C-band SAR (10 m, VV/VH), OPERA RTC-S1 terrain-corrected SAR (Sentinel-1 derived), VIIRS nighttime lights (NASA Black Marble, ~500 m), and NASA FIRMS active fire (375 m, daily). You can also upload your own GeoTIFF, COG, or GeoJSON data.

Sentinel-2 Optical

Optical

ESA Copernicus Programme

High-resolution multispectral optical imagery. Thirteen spectral bands from visible through near-infrared and shortwave infrared make it the workhorse for vegetation, land cover, and water analysis.

Resolution

10 m (visible/NIR)

Bands

13 spectral bands

Revisit

~5 days (constellation)

Level

L2A surface reflectance

Typical uses: True color and false color composites, NDVI / EVI / NDWI vegetation and water indices, crop and forest monitoring, land-cover change.

Attribution: Contains modified Copernicus Sentinel data [year]

Open Sentinel-2 Viewer

Sentinel-1 C-Band SAR

Radar

ESA Copernicus Programme

C-band Synthetic Aperture Radar that images the surface day or night and sees straight through cloud, smoke, and light rain. Delivered as GRD products in VV and VH polarizations.

Resolution

~10 m (IW mode)

Polarization

VV, VH

Revisit

6-day repeat cycle

Frequency

C-band, 5.405 GHz

Typical uses: Flood mapping, surface-change detection, vessel detection, and all-weather monitoring where optical imagery is blocked by clouds.

Attribution: Contains modified Copernicus Sentinel data [year]

Open Sentinel-1 SAR Viewer

OPERA RTC-S1

Analysis-Ready SAR

NASA JPL via Alaska Satellite Facility (ASF)

Analysis-ready, Radiometrically Terrain Corrected backscatter derived from Sentinel-1 (C-band). Terrain correction with a DEM makes backscatter values comparable across slopes — ideal for quantitative and time-series work in hilly terrain.

Source

Sentinel-1 (C-band)

Processing

Radiometric Terrain Correction

Format

Cloud-Optimized GeoTIFF

Distributor

ASF DAAC

Typical uses: Time-series backscatter comparison, terrain-aware change detection, and SAR analysis where consistent radiometry matters.

Attribution: OPERA RTC courtesy NASA/JPL-Caltech

Explore SAR imagery

VIIRS Nighttime Lights

Nighttime

NASA Black Marble (VNP46A2)

The VIIRS Day/Night Band measures visible light at night. NASA Black Marble products are calibrated and atmospherically corrected, turning city lights into a proxy for human activity.

Resolution

~500 m

Product

Black Marble VNP46A2

Revisit

Daily

Sensor

VIIRS Day/Night Band

Typical uses: Tracking urban development and electrification, estimating economic activity, and detecting power outages after disasters.

Attribution: NASA Black Marble VNP46A2

Open Nighttime Lights

NASA FIRMS Active Fire

Active Fire

NASA FIRMS

Near real-time thermal fire detections from VIIRS and MODIS. Hotspots are updated daily and overlaid directly on the map — no account or API key required to browse.

Resolution

375 m (VIIRS), 1 km (MODIS)

Latency

Near real-time, daily

Sensors

VIIRS, MODIS thermal

Cost

Free to browse

Typical uses: Wildfire situational awareness, monitoring fire spread, and correlating thermal anomalies with events on the Watchfloor.

Attribution: NASA FIRMS

Open Active Fire Map

Your Own Data

Bring Your Own

Uploaded by you

Bring GeoTIFF, Cloud-Optimized GeoTIFF, or GeoJSON files and combine them with satellite imagery on a single map. Your data stays alongside the open sources for custom analysis.

Raster

GeoTIFF, COG

Vector

GeoJSON

Use

Overlay with satellite layers

Reference

OpenStreetMap basemaps

Typical uses: Overlaying field boundaries, custom AOIs, survey results, or third-party rasters together with Sentinel and VIIRS imagery.

Attribution: You retain ownership of uploaded data

Upload Your Data

Attribution & Licensing

All satellite sources come from free and open programmes. When you export or publish imagery, include the relevant attribution below.

Sentinel-1 & Sentinel-2

European Space Agency (ESA) Copernicus Programme

"Contains modified Copernicus Sentinel data [year]"

VIIRS Nighttime Lights

NASA Black Marble (VNP46A2)

"NASA Black Marble VNP46A2"

OPERA RTC-S1

NASA JPL via Alaska Satellite Facility

"OPERA RTC courtesy NASA/JPL-Caltech"

NASA FIRMS Active Fire

NASA Fire Information for Resource Management System

"NASA FIRMS"

Reference Layers

OpenStreetMap contributors

"© OpenStreetMap contributors"

Your Own Data

Uploaded GeoTIFF / COG / GeoJSON

You retain ownership of uploaded data

Frequently Asked Questions

Is the satellite data free?
The underlying data — Sentinel-1, Sentinel-2, VIIRS, and NASA FIRMS — comes from free and open programmes (ESA Copernicus and NASA). Browsing events and the map is free; tokens are only spent when you load satellite imagery tiles or run analysis.
What is the difference between Sentinel-1 and Sentinel-2?
Sentinel-1 is radar (SAR): it works through clouds, day or night, and is ideal for flood and surface-change detection. Sentinel-2 is optical: it captures natural-looking, high-resolution imagery in 13 bands, best for vegetation and land-cover analysis. They are highly complementary.
Is OPERA RTC-S1 the same as NISAR L-band SAR?
No. The OPERA RTC product in Off-Nadir Delta is OPERA RTC-S1, derived from Sentinel-1 — that is C-band radar, not L-band. It is terrain-corrected, analysis-ready backscatter distributed by the Alaska Satellite Facility.
How often is each source updated?
Sentinel-2 revisits roughly every 5 days, Sentinel-1 every 6 days, and VIIRS and NASA FIRMS provide daily coverage. Actual availability over a given location depends on orbit passes and, for optical imagery, cloud cover.
Do I need to credit the data sources?
Yes. When you export or publish imagery, include the attribution listed for each source — for example, "Contains modified Copernicus Sentinel data" for Sentinel-1/2, "NASA Black Marble VNP46A2" for VIIRS, and "NASA FIRMS" for active fire data.
Can I add my own data?
Yes. Upload GeoTIFF, Cloud-Optimized GeoTIFF, or GeoJSON files and overlay them with the satellite sources on a single map. Reference layers such as OpenStreetMap basemaps are also available for context.

Start Exploring These Sources

Open Sentinel-1, Sentinel-2, OPERA RTC-S1, VIIRS, and NASA FIRMS data with a free account.