Off-Nadir Delta
Area Monitoring

Satellite Area Monitoring

Draw any area on the map. The satellite keeps watching. Track how a place changes over time — automatically, with no GIS software and no code.

Quick Answer: Satellite area monitoring means repeatedly observing a fixed area with satellite imagery to detect change over time. You draw a polygon, choose a metric (NDVI, SAR backscatter, NDWI), and a time series is built automatically. Off-Nadir Delta does this in the browser — no GIS software, no code — and flags anomalies when readings deviate ±2σ from their seasonal baseline.

Draw & Watch

Draw any polygon on Earth and the area is monitored continuously — no manual re-checking.

Automatic Time Series

Every satellite pass is analyzed and appended to a continuous time series of your chosen metric.

Anomaly Alerts

Readings that deviate ±2σ from the seasonal baseline are flagged so change never slips past you.

Multi-Index

Track several indices over the same area to tell different change events apart with confidence.

All-Weather

Sentinel-1 SAR monitoring sees through clouds, day or night, so coverage continues during storms.

No GIS, No Code

Everything runs in the browser. No QGIS, no Earth Engine scripts, no downloads — just draw and go.

What Is Satellite Area Monitoring?

Satellite area monitoring is the practice of repeatedly observing the same geographic area with satellite imagery to detect and measure how it changes over time. Rather than interpreting a single snapshot, you build a time series of a chosen metric for a fixed polygon — so trends, seasonal cycles, and sudden events all become visible and quantifiable.

The metric you track depends on what you care about. NDVI and related indices follow vegetation health; SAR backscatter follows surface and structural change and works through clouds; NDWI follows water extent; and nighttime lights follow human activity. Tracking several at once — multi-index monitoring — lets you distinguish, for example, a harvest from a flood from deforestation.

Historically this required desktop GIS or code-based platforms. The shift that matters is no-code, browser-based monitoring: you draw an area, pick what to track, and the system handles imagery search, computation, time-series assembly, and anomaly detection for you. See the full step-by-step guide.

How It Works

1

Draw Your Area

Pan to any location on Earth and draw a polygon around the area you want to watch — a field, forest, coastline, construction site, or city block.

2

Choose What to Track

Pick one or more satellite indices — NDVI for vegetation, SAR backscatter for all-weather surface change, NDWI for water, nighttime lights, and more.

3

Let Satellites Watch

Each time a satellite passes over, the area is re-analyzed automatically and added to a continuous time series — no manual checking.

4

Get Alerted to Change

When a reading deviates from its seasonal baseline (±2σ), the area is flagged so you can investigate what changed and when.

Frequently Asked Questions

What is satellite area monitoring?▼
Satellite area monitoring is the practice of repeatedly observing a fixed geographic area with satellite imagery over time to detect and measure change. Instead of viewing a single image, you build a time series of a chosen metric — such as NDVI (vegetation), SAR backscatter (surface/structure), or NDWI (water) — for the same polygon, so gradual or sudden changes become visible and measurable.
Can I monitor an area without GIS software?▼
Yes. Traditional area monitoring required desktop GIS (like QGIS or ArcGIS) or code-based platforms (like Google Earth Engine). Off-Nadir Delta runs entirely in your browser: you draw an area, choose what to track, and the time series is built automatically — no installation, no scripting, and no data downloads.
How does automated change detection work?▼
For each new satellite pass, the selected index is recomputed over your area and compared against its historical baseline. When a value falls outside the expected range (commonly ±2 standard deviations from the seasonal mean), it is flagged as an anomaly. This statistical approach distinguishes genuine change from normal seasonal variation.
Which satellites and indices can I monitor?▼
Common choices include Sentinel-2 optical indices (NDVI, EVI, SAVI, NDWI, NDBI, NBR), Sentinel-1 SAR backscatter (VV/VH, works through clouds day or night), and VIIRS nighttime lights. Combining multiple indices over the same area — multi-index monitoring — lets you tell different change events apart.
What can satellite area monitoring be used for?▼
Typical uses include tracking deforestation and forest health, monitoring crop growth and irrigation, detecting flooding, watching construction and urban expansion, observing coastline and water-body change, and verifying environmental compliance. Any area whose surface changes over time is a candidate.
How often is an area updated?▼
Update frequency depends on the satellite. Sentinel-2 optical revisits roughly every 5 days (more often when combined with Landsat via HLS), and Sentinel-1 SAR every 6–12 days. SAR is especially valuable because it is not blocked by clouds, so monitoring continues during storms and at night.
Is satellite area monitoring free?▼
You can start free. Off-Nadir Delta offers a free tier to set up and run area monitoring, with paid plans for higher usage such as more monitored areas and more frequent automated re-analysis. See the pricing page for current details.

Related Resources

How to Monitor Any Area

Step-by-step time-series monitoring guide

Learn more

No-Code GEE Alternative

Monitor areas without writing code

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Multi-Index Monitoring

Why one sensor is never enough

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Anomaly Detection

How ±2σ change alerts work

Learn more

Vegetation Time Series

Monitor NDVI over any area

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SAR Time-Series Monitoring

All-weather change detection

Learn more

Choosing an Index

Pick the right metric to track

Learn more

Start Monitoring Any Area

Draw your first area and let the satellites keep watching. Free to start — no GIS software, no code.

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