Chapter two Image classification by Remote sensing
- 1. Remote Sensing Image 1 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 2. Unit 2: Remote Sensing Image 2.1. General Overview of Remote Sensing Imagery ❖Remote sensing imagery involves the acquisition of information about the Earth's surface from a distance, typically using sensors mounted on aircraft, satellites, drones, or other platforms. ❖It allows for the collection of data without physical contact with the object or area of interest. ❖Satellite imagery is collected by a host of national and international government and private agencies. ❖Most of this data is protected by copyright and use access has to be negotiated by individual users or institutions. ❖Free access is possible through collaboration with NASA and NASA- funded institutions. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 3. ❖ Satellite imagery has resulted from a technical process called Remote Sensing. ❖ Satellite imagery provides important contextual information for a GIS and is often used to conduct heads-up digitizing whereby features from the image are converted into vector datasets. ❖ Remote sensing imagery can be categorized into different types based on the electromagnetic spectrum they capture, including: ❖ Visible Light Imagery: These images capture the portion of the electromagnetic spectrum that is visible to the human eye. ❖ They are often used for visual interpretation and analysis of features on the Earth's surface. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 4. ✓Infrared Imagery: Infrared sensors capture radiation beyond the visible spectrum. ✓They are useful for applications such as vegetation analysis, heat mapping, and identifying geological features. ✓Thermal Imagery: Thermal sensors detect heat radiation emitted by objects. ✓They are valuable for applications like monitoring urban heat islands, analyzing volcanic activity, and detecting wildfires. ✓Radar Imagery: Radar (Radio Detection and Ranging) sensors emit microwave signals and measure the signals reflected back from objects. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 5. ✓Radar imagery is useful for applications such as mapping terrain, monitoring changes in land cover, and detecting changes in surface elevation. ✓LiDAR (Light Detection and Ranging) Imagery: LiDAR systems emit laser pulses and measure the time it takes for the pulses to return after hitting objects. ✓LiDAR data are valuable for creating highly detailed 3D maps of terrain, vegetation, and man-made structures. ✓Remote sensing imagery is widely used in various fields, including agriculture, forestry, environmental monitoring, urban planning, disaster management, and defense. ✓It provides valuable awareness into Earth's surface and atmosphere, enabling scientists, researchers, and decision-makers to make informed decisions and solve complex problems. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 6. 2.2. Types of remote sensing imagery, sources and their image characteristics • Remote sensing imagery encompasses various types of data collected from different sources, each offering unique characteristics and applications. • Here's an overview of the common types of remote sensing imagery, their sources, and their key image characteristics: 2.2.1. Digital Aerial Photos: • Digital aerial photos are captured using specialized cameras mounted on aircraft. • They provide high-resolution imagery of the Earth's surface, offering detailed information about terrain, land cover, and infrastructure. • Aerial photos are commonly used in urban planning, environmental assessment, forestry, and archaeology. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 7. ✓The Digital Aerial Photo is the digital aerial photograph captured by the large format digital aerial camera which was put in commission in mid-2016. ✓The digital aerial camera can capture five spectral bands of information (Panchromatic, Red, Green, Blue, and Near-infrared). ✓The DAP is suitable for photogrammetric measurement. ✓The DAP is provided in TIFF Format and the delivering/carrying media is DVD. ✓The file size of Black & White and Color aerial photograph images is about 300MB and 1.1GB respectively. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 8. ❖Image Characteristics of DAP • High spatial resolution, providing detailed views of the Earth's surface. • Rich color information, enabling accurate interpretation of land cover and features. • Can cover large areas in a single flight, offering flexibility in data acquisition. ❖Applications: Urban planning, environmental assessment, forestry, archaeology, and infrastructure monitoring. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 9. 2. Multispectral Satellite Image: ✓Source: Multispectral satellite imagery is collected by satellites orbiting the Earth. ✓Image Characteristics: ▪ Captures data across multiple spectral bands, including visible, near-infrared, and thermal wavelengths. ▪ Provides information about vegetation health, land use, soil moisture, and environmental changes. ▪ Offers medium to high spatial resolution, suitable for regional- scale analysis and monitoring. ❖Applications: Agriculture, forestry, environmental monitoring, land cover classification, and disaster management. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 10. ✓Multispectral images with more numerous bands or finer spectral resolution or wider spectral coverage may be called "hyper- spectral" or "ultra-spectral". ✓Multi-spectral imaging can capture light from frequencies beyond the visible light range, such as infrared and thermal bands. ✓This can allow the extraction of additional information that the human eye fails to capture with its receptors for red, green, and blue. ✓Multi-spectral images are the main type of images acquired by Remote sensing (RS) radiometers. ✓Multi-spectral is the opposite of panchromatic. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 11. ✓Usually, satellites have 3 to 7 or more radiometers (Landsat has 7). ✓A multispectral image is therefore composed of several channels or bands, each one containing, the amount of radiation measured in very specific wavelength ranges for each pixel (for example, green, red, or near infra-red). Spectral bands ▪ The wavelengths are approximate; exact values depend on the particular satellite's instruments: ▪ Blue, 450-guatda.com/cmx.p515...520 nm, used for atmospheric and deep-water imaging. Can reach within 150 feet (46m) deep in clear water. ▪ Green, 515...520-guatda.com/cmx.p590...600 nm, used for imaging of vegetation and deep-water structures, up to 90 feet (27m) in clear water. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 12. • Red, 600...630-guatda.com/cmx.p680...690 nm, used for imaging of man-made objects, water up to 30 feet (9.1 m) deep, soil, and vegetation. • Near infrared, 750-900 nm, primarily for imaging of vegetation. • Mid-infrared, 1550-1750 nm, for imaging vegetation and soil moisture content, and some forest fires. • Mid-infrared, 2080-2350 nm, for imaging soil, moisture, geological features, silicates, clays, and fires. • Thermal infrared, 10400-12500 nm, uses emitted radiation instead of reflected, for imaging of geological structures, thermal differences in water currents, fires, and for night studies. • Radar and related technologies, useful for mapping terrain and for detecting various objects. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 13. 3. High and Low-Resolution Satellite Imagery: ✓Source: High and low-resolution satellite imagery is acquired from Earth observation satellites. ✓Image Characteristics: ▪ High-resolution imagery offers detailed views of the Earth's surface with spatial resolutions ranging from a few centimeters to several meters per pixel. ▪ Low-resolution imagery covers larger areas but with lower spatial detail, typically ranging from tens to hundreds of meters per pixel. ▪ Both types of imagery provide valuable information for mapping, monitoring, and analysis. ✓Applications: High-resolution imagery is valuable for urban planning, infrastructure development, disaster response, environmental monitoring, and military intelligence. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 14. ✓ Low-resolution imagery is useful for regional and global-scale analysis. ✓High-resolution satellite images are a rich source of geospatial information. • Nowadays, these images contain the finest spectral and spatial information of ground realities in the different electromagnetic spectrums. • Many image processing software, algorithms, and techniques are available to extract such information from these images. • Multi spectral as well as panchromatic (PAN) high-resolution satellite images are missing, one important information, regarding ground features and realities is that information is attribute information that is not directly available in high-resolution satellite images. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 15. ▪ From the very first day, this information used to be collected through indirect ways using GPS, digitizing, geo-coding, geo- tagging, field survey, and many other techniques. ▪ Our real world has vertical labels for ground observers to identify and use this information. ▪ These vertical labels are present in the form of names, logos, icons, symbols, and numbers. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 16. 4. Microwave (RADAR) Image: • Source: Microwave imagery is collected using RADAR (Radio Detection and Ranging) sensors onboard satellites. • Image Characteristics: o Penetrates clouds, vegetation, and soil, allowing imaging regardless of weather conditions or time of day. o Provides information about terrain elevation, land cover, and surface roughness. o Can detect changes in land surface features and monitor natural disasters such as floods and landslides. • Applications: Terrain mapping, vegetation monitoring, flood detection, disaster assessment, military surveillance, detecting forest biomass, and assessing soil moisture content. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 17. ▪ RADAR imagery is particularly valuable in regions prone to cloud cover or frequent precipitation. ▪ Imaging radar works very like a flash camera in that it provides its own light to illuminate an area on the ground and take a snapshot picture, but at radio wavelengths. ▪ A flash camera sends out a pulse of light (the flash) and records on film the light that is reflected back at it through the camera lens. ▪ Instead of a camera lens and film, radar uses an antenna and digital computer tapes to record its images. ▪ In a radar image, one can see only the light that was reflected back towards the radar antenna. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 18. 5. Laser Scanning (LiDAR) Image: • Source: Laser scanning, also known as Light Detection and Ranging (LiDAR), is conducted using airborne or terrestrial LiDAR systems. • Image Characteristics: o Measures distances to the Earth's surface using laser pulses, creating detailed three-dimensional models. o Provides accurate elevation data, allowing for terrain mapping, forest inventory, and urban planning. o Can penetrate vegetation to reveal underlying terrain features and structures. • Applications: Terrain modeling, forest inventory, urban planning, flood mapping, infrastructure management, and archaeological mapping. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 19. ✓LiDAR is a technique for capturing geospatial data that uses laser scanning to create three-dimensional point clouds of geographic features. ✓It is an active remote sensing system which means that the system itself generates energy - in this case, light – to measure things on the ground. ✓LiDAR sensors can be mounted on UAVs, airplanes, or satellites. ✓LiDAR is fundamentally a distance technology. ✓From an airplane or helicopter, LiDAR systems send light to the ground. ✓This pulse hits the ground and returns to the sensor. ✓Then, it measures how long it takes for the light to return back to the sensor. ✓By recording the return time, this is how LiDAR measures distance. ✓In fact, this is also how LiDAR got its name Light Detection and Ranging. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 20. 6. Hyperspectral Image: • Source: Hyperspectral imagery is collected using sensors that capture data across numerous narrow spectral bands. • Image Characteristics: o Offers detailed spectral information, allowing for the identification and characterization of surface materials and biochemical compositions. o Provides enhanced discrimination of features and substances compared to multispectral imagery. • Applications: Mineral exploration, crop health assessment, environmental monitoring, precision agriculture, forestry, geology, and military reconnaissance. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 21. ▪ Hyperspectral imaging, like other spectral imaging, collects and processes information from across the electromagnetic spectrum. ▪ The goal of hyperspectral imaging is to obtain the spectrum for each pixel in the image of a scene, to find objects, identify materials, or detect processes. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 22. 7. UAV/Drone Image: • Source: UAV or drone imagery is captured using unmanned aerial vehicles equipped with cameras or other sensors. • Image Characteristics: o Offers high spatial resolution and flexibility in data acquisition for various applications. o Enables close-range and low-altitude data collection, providing detailed views of the Earth's surface. o Allows rapid deployment and collection of data in areas that may be inaccessible or hazardous to manned aircraft. • Applications: Agriculture, environmental monitoring, infrastructure inspection, disaster response, surveying, and mapping. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 23. ✓Drone imagery provides high-resolution, flexible, and cost-effective data acquisition for various applications, including agriculture, environmental monitoring, infrastructure inspection, and disaster response. ✓Understanding the characteristics and applications of different types of remote sensing imagery is crucial for effectively utilizing remote sensing data in various fields such as environmental science, agriculture, urban planning, disaster management, and resource exploration. ✓Each type of imagery offers unique capabilities and advantages, allowing for comprehensive analysis and interpretation of Earth's surface features and processes. 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC
- 24. Thanks for your attention! 2/17/2024 Prepared by Milkessa Dangia, WU 2024/2016EC