What kinds of problems will you learn to solve in the Blended Learning course on Change Detection and Time Series?
- How do you identify changes in vegetation, water, buildings, and land use using satellite images from different time periods?
- How do you determine where a change has occurred, when it began, and how significant it is?
- How do you distinguish temporary and seasonal changes from structural developments?
- How do you use longer satellite time series to identify trends, anomalies, and turning points?
- How do you translate changes and trends in satellite data into reliable information for monitoring and spatial decision-making?
During this Blended Learning course on Change Detection and Time Series, you’ll learn how to use satellite imagery from different periods to identify, analyze, and monitor changes on the Earth’s surface. You’ll work with time series from sources such as Sentinel and Landsat and learn to distinguish changes from normal variation. This will enable you to systematically track developments in landscape, vegetation, water, nature, and built-up areas.
The Theory Behind Change Detection
Change detection begins by comparing observations of the same area at different times. It is important that differences in satellite images are actually the result of changes on the Earth’s surface and are not caused by, for example, cloud cover, shadows, seasons, differences between sensors, or imaging conditions.
You will therefore learn which factors influence the comparability of satellite images and how to distinguish between actual changes and temporary variations. You will also be introduced to various forms of change detection, such as comparing images, spectral bands, indices, and land-cover maps.
From Two Satellite Images to Time Series
Comparing two points in time can reveal what has changed between two images. A time series goes further and reveals how an area evolves over months, years, or even decades. This allows you not only to detect changes but also to determine when they occur and whether they represent a temporary anomaly or a structural trend.
You will learn to organize satellite observations chronologically and recognize patterns over time. In doing so, you will pay attention to seasonal influences, trends, sudden changes, and deviations from normal patterns. Longer time series, for example, make it possible to distinguish gradual changes in vegetation, urbanization, or land use from short-term events such as droughts, floods, or wildfires. Time series analysis therefore plays an increasingly important role in continuous monitoring using remote sensing.
Working with Sentinel and Landsat Time Series
For change detection, satellite programs with regular and long-term observations are particularly valuable. You will therefore work with open-access satellite data from sources such as Sentinel and Landsat and learn to select appropriate images and time periods for various monitoring questions.
You will explore how spectral bands, indices, and classified images can be compared over time. This allows you, for example, to track changes in vegetation, surface water, land cover, and urban areas. You’ll also learn how existing European land-cover products and change layers can be used as supplementary information and references. The Copernicus Land Monitoring Service, for example, offers land-cover products and specific change layers for analyzing changes over time.
Analyzing Changes and Trends
After covering the theoretical foundation, you’ll analyze changes yourself. You’ll learn to visually identify differences between successive satellite images and explore how to determine the extent, direction, and rate of change.
For longer time series, you’ll analyze developments by combining multiple observations. You’ll examine trends, recurring patterns, anomalies, and potential turning points. This provides a more complete picture than comparing just two points in time. Modern change-detection methods therefore increasingly rely on dense time series to identify complex changes more reliably.
The analyses are performed using open data and open-source techniques. QGIS serves as a key working environment for combining, analyzing, and visualizing spatial and temporal data. The focus is not on the software itself, but on determining which analysis method is needed to reliably identify a change.
From Change to Monitoring and Insight
During the Blended Learning course, you’ll work with realistic real-world examples and satellite data from different time periods. You’ll not only investigate where changes are occurring but also attempt to explain what the observed patterns mean and how this information can be used for monitoring.
You’ll work on assignments such as:
- Compare satellite images from different years and spatially map changes in land cover.
- Analyze a vegetation time series and distinguish seasonal patterns from structural changes.
- Investigate changes in surface water and determine when and where they occur.
- Map the expansion of built-up areas or changes in land use over a longer period.
- Detect sudden changes, such as wildfires, floods, or significant vegetation loss, and analyze the subsequent recovery.
- Convert a satellite time series into maps, graphs, and conclusions that can be used to monitor developments in an area.
Upon completion, you will be able to independently compare satellite images from different periods and use time series to identify changes, trends, and anomalies. You will be able to distinguish between temporary and structural changes and translate the results into actionable information for monitoring, management, and spatial decision-making.