Microwave Remote Sensing

Active and passive microwave remote sensing are two distinct methods used in the field of remote sensing to collect information about the Earth's surface and atmosphere using microwave radiation. Let's explore the principles of each:

1. Active Microwave Remote Sensing:

- Principle: Active microwave remote sensing involves the transmission of microwave pulses from a sensor or satellite to the Earth's surface. These pulses are then reflected or scattered back to the sensor, where they are received and analyzed to gather information about the target area.

- Key Features:

- Microwave Source: An active microwave sensor emits microwave radiation (usually in the form of radar pulses) towards the Earth.

- Reflection and Scattering: When the microwave pulses encounter objects on the Earth's surface, they interact with them. Some of the energy is reflected back to the sensor, while the rest is scattered.

- Distance Measurement: By measuring the time it takes for the microwave pulses to travel to the target and return (time-of-flight), active microwave remote sensing can calculate the distance to the target.

- Applications: Active microwave remote sensing is used for applications such as topographic mapping, vegetation monitoring, and soil moisture estimation. Synthetic Aperture Radar (SAR) is a common example of an active microwave sensor.

2. Passive Microwave Remote Sensing:

- Principle: Passive microwave remote sensing, on the other hand, relies on the detection of naturally occurring microwave radiation emitted or scattered by the Earth's surface and atmosphere. Instead of actively transmitting microwave signals, passive sensors measure the microwave radiation already present.

- Key Features:

- Microwave Receiver: Passive microwave sensors have specialized receivers that can detect microwave emissions from the Earth.

- Spectral Bands: These sensors are sensitive to specific microwave frequencies or spectral bands, which correspond to different properties of the Earth's surface or atmosphere.

- Applications: Passive microwave remote sensing is often used for monitoring atmospheric conditions (e.g., weather forecasting), sea surface temperature, sea ice concentration, and soil moisture. It is particularly valuable for studying the Earth's energy balance.

In summary, active microwave remote sensing involves sending out microwave pulses and measuring their reflections or scattering, while passive microwave remote sensing relies on naturally emitted or scattered microwave radiation. Each method has its unique applications and advantages, making them valuable tools for Earth observation and scientific research.

Comments

Accuracy Assessment

Accuracy assessment is the process of checking how correct your classified satellite image is . 👉 After supervised classification, the satellite image is divided into classes like: Water Forest Agriculture Built-up land Barren land But classification is done using computer algorithms, so some areas may be wrongly classified . 👉 Accuracy assessment helps to answer this question: ✔ "How much of my classified map is correct compared to real ground conditions?" Goal The main goal is to: Measure reliability of classified maps Identify classification errors Improve classification results Provide scientific validity to research 👉 Without accuracy assessment, a classified map is not considered scientifically reliable . Reference Data (Ground Truth Data) Reference data is real-world information used to check classification accuracy. It can be collected from: ✔ Field survey using GPS ✔ High-resolution satellite images (Google Earth etc.) ✔ Existing maps or survey reports 🧭 Exampl...

Landsat 8 Band designation and Band Combination.

Landsat 8 Band designation and Band Combination. Landsat 8-9 Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS) Bands Wavelength (micrometers) Resolution (meters) Band 1 - Coastal aerosol 0.43-0.45 30 Band 2 - Blue 0.45-0.51 30 Band 3 - Green 0.53-0.59 30 Band 4 - Red 0.64-0.67 30 Band 5 - Near Infrared (NIR) 0.85-0.88 30 Band 6 - SWIR 1 1.57-1.65 30 Band 7 - SWIR 2 2.11-2.29 30 Band 8 - Panchromatic 0.50-0.68 15 Band 9 - Cirrus 1.36-1.38 30 Band 10 - Thermal Infrared (TIRS) 1 10.6-11.19 100 Band 11 - Thermal Infrared (TIRS) 2 11.50-12.51 100 Vineesh V Assistant Professor of Geography, Directorate of Education, Government of Kerala. https://www.facebook.com/Applied.Geography http://geogisgeo.blogspot.com

Change Detection

Change detection is the process of finding differences on the Earth's surface over time by comparing satellite images of the same area taken on different dates . After supervised classification , two classified maps (e.g., Year-1 and Year-2) are compared to identify land use / land cover changes . Goal To detect where , what , and how much change has occurred To monitor urban growth, deforestation, floods, agriculture, etc. Basic Concept Forest → Forest = No change Forest → Urban = Change detected Key Terminologies Multi-temporal images : Images of the same area at different times Post-classification comparison : Comparing two classified maps Change matrix : Table showing class-to-class change Change / No-change : Whether land cover remains same or different Main Methods Post-classification comparison – Most common and easy Image differencing – Subtract pixel values Image ratioing – Divide pixel values Deep learning methods – Advanced AI-based detection Examples Agricult...

Landsat band composition

Short-Wave Infrared (7, 6 4) The short-wave infrared band combination uses SWIR-2 (7), SWIR-1 (6), and red (4). This composite displays vegetation in shades of green. While darker shades of green indicate denser vegetation, sparse vegetation has lighter shades. Urban areas are blue and soils have various shades of brown. Agriculture (6, 5, 2) This band combination uses SWIR-1 (6), near-infrared (5), and blue (2). It's commonly used for crop monitoring because of the use of short-wave and near-infrared. Healthy vegetation appears dark green. But bare earth has a magenta hue. Geology (7, 6, 2) The geology band combination uses SWIR-2 (7), SWIR-1 (6), and blue (2). This band combination is particularly useful for identifying geological formations, lithology features, and faults. Bathymetric (4, 3, 1) The bathymetric band combination (4,3,1) uses the red (4), green (3), and coastal bands to peak into water. The coastal band is useful in coastal, bathymetric, and aerosol studies because...

Development and scope of Environmental Geography and Recent concepts in environmental Geography

Environmental Geography studies the relationship between humans and nature in a spatial (place-based) way. It combines Physical Geography (natural processes) and Human Geography (human activities). A. Early Stage 🔹 Environmental Determinism Concept: Nature controls human life. Meaning: Climate, landforms, and soil decide how people live. Example: People in deserts (like Sahara Desert) live differently from people in fertile river valleys. 🔹 Possibilism Concept: Humans can modify nature. Meaning: Environment gives options, but humans make choices. Example: In dry areas like Rajasthan, people use irrigation to grow crops. 👉 In this stage, geography was mostly descriptive (explaining what exists). B. Evolution Stage (Mid-20th Century) Environmental problems increased due to: Industrialization Urbanization Deforestation Pollution Geographers started studying: Environmental degradation Resource management Human impact on ecosystems The field became analytical and problem-solving...

Vineesh V, Geography

Search This Blog