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Santiago Nguyen
Santiago Nguyen

Multispectral Images [UPD]


Multispectral imaging captures image data within specific wavelength ranges across the electromagnetic spectrum. The wavelengths may be separated by filters or detected with the use of instruments that are sensitive to particular wavelengths, including light from frequencies beyond the visible light range, i.e. infrared and ultra-violet. It can allow extraction of additional information the human eye fails to capture with its visible receptors for red, green and blue. It was originally developed for military target identification and reconnaissance. Early space-based imaging platforms incorporated multispectral imaging technology[1] to map details of the Earth related to coastal boundaries, vegetation, and landforms.[2] Multispectral imaging has also found use in document and painting analysis.[3][4]




Multispectral Images



Multispectral imaging measures light emission and is often used in detecting or tracking military targets. In 2003, researchers at the United States Army Research Laboratory and the Federal Laboratory Collaborative Technology Alliance reported a dual band multispectral imaging focal plane array (FPA). This FPA allowed researchers to look at two infrared (IR) planes at the same time.[6] Because mid-wave infrared (MWIR) and long wave infrared (LWIR) technologies measure radiation inherent to the object and require no external light source, they also are referred to as thermal imaging methods.


For nighttime target detection, thermal imaging outperformed single-band multispectral imaging. Dual band MWIR and LWIR technology resulted in better visualization during the nighttime than MWIR alone. Citation Citation. The US Army reports that its dual band LWIR/MWIR FPA demonstrated better visualizing of tactical vehicles than MWIR alone after tracking them through both day and night.[citation needed]


By analyzing the emissivity of ground surfaces, multispectral imaging can detect the presence of underground missiles. Surface and sub-surface soil possess different physical and chemical properties that appear in spectral analysis.[8] Disturbed soil has increased emissivity in the wavelength range of 8.5 to 9.5 micrometers while demonstrating no change in wavelengths greater than 10 micrometers.[6] The US Army Research Laboratory's dual MWIR/LWIR FPA used "red" and "blue" detectors to search for areas with enhanced emissivity. The red detector acts as a backdrop, verifying realms of undisturbed soil areas, as it is sensitive to the 10.4 micrometer wavelength. The blue detector is sensitive to wavelengths of 9.3 micrometers. If the intensity of the blue image changes when scanning, that region is likely disturbed. The scientists reported that fusing these two images increased detection capabilities.[6]


Most radiometers for remote sensing (RS) acquire multispectral images. Dividing the spectrum into many bands, multispectral is the opposite of panchromatic, which records only the total intensity of radiation falling on each pixel.[11] Usually, Earth observation satellites have three or more radiometers. Each acquires one digital image (in remote sensing, called a 'scene') in a small spectral band. The bands are grouped into wavelength regions based on the origin of the light and the interests of the researchers.


In the case of Landsat satellites, several different band designations have been used, with as many as 11 bands (Landsat 8) comprising a multispectral image.[14][15][16] Spectral imaging with a higher radiometric resolution(involving hundreds or thousands of bands), finer spectral resolution (involving smaller bands), or wider spectral coverage may be called hyperspectral or ultraspectral.[17][16]


Unlike other aerial photographic and satellite image interpretation work, these multispectral images do not make it easy to identify directly the feature type by visual inspection. Hence the remote sensing data has to be classified first, followed by processing by various data enhancement techniques so as to help the user to understand the features that are present in the image.


Having a higher level of spectral detail in hyperspectral images gives the better capability to see the unseen. For example, hyperspectral remote sensing distinguished between 3 minerals because of their high spectral resolution. But the multispectral Landsat Thematic Mapper could not distinguish between the 3 minerals.


There are hundreds more applications where multispectral and hyperspectral enable us to understand the world. For example, we use it in the fields of agriculture, ecology, oil and gas, atmospheric studies, and more.


Which satellite and what will be the combination of bandwidth to be used to work with forest tree canopy and what are the other things that we should focus on if we want to work with satellite images.


Abstract:Unmanned Aerial Vehicles (UAV)-based remote sensing offers great possibilities to acquire in a fast and easy way field data for precision agriculture applications. This field of study is rapidly increasing due to the benefits and advantages for farm resources management, particularly for studying crop health. This paper reports some experiences related to the analysis of cultivations (vineyards and tomatoes) with Tetracam multispectral data. The Tetracam camera was mounted on a multi-rotor hexacopter. The multispectral data were processed with a photogrammetric pipeline to create triband orthoimages of the surveyed sites. Those orthoimages were employed to extract some Vegetation Indices (VI) such as the Normalized Difference Vegetation Index (NDVI), the Green Normalized Difference Vegetation Index (GNDVI), and the Soil Adjusted Vegetation Index (SAVI), examining the vegetation vigor for each crop. The paper demonstrates the great potential of high-resolution UAV data and photogrammetric techniques applied in the agriculture framework to collect multispectral images and evaluate different VI, suggesting that these instruments represent a fast, reliable, and cost-effective resource in crop assessment for precision farming applications.Keywords: unmanned aerial vehicles; vegetation; agriculture; multispectral; photogrammetry; vegetation indices; crops


Multispectral imaging captures light from a narrow range of wavelengths across the electromagnetic spectrum. Multispectral images are captured either with special cameras that separate these wavelengths using filters, or with instruments that are sensitive to particular wavelengths, including light from frequencies that are invisible to the human eye (infrared and ultra-violet, for example).


Your traditional digital camera captures the light that falls onto the sensor. The sensor captures images in the same way that your eye perceives color. To do this, your camera uses wideband filters to divide the light into three channels: red, green and blue (RGB). A multispectral camera, on the other hand, captures information that is neither available to the human observer, nor to a typical RGB camera.


Landsat satellites use multispectral sensors help analysts study land use and land cover change, vegetation and agricultural production trends and cycles, water and environmental quality, soils, geology, and other earth resource and science problems. In fact, Landsat has been one of the most important sources of mid-resolution multispectral data globally.


Multispectral imaging is also used to detect land mines and underground missiles by analyzing the emissivity of ground surfaces. Drones flown over former battlefields use a camera that acquires registered images in six spectral bands.These images are then analyzed using software that identifies metal and plastic land mines.


Soil on the surface and soil beneath the surface possess different physical and chemical properties that can be detected with multispectral analysis. Disturbed soil features increased emissivity in a specific wavelength, and analyzing images of this soil helps military commanders to identify likely locations of land mines. Detection of recently buried land-mines and improvised explosive devices using multispectral imaging is a growing field.


Multispectral imaging is also used to interpret ancient papyri and other documents from antiquity by imaging the documents in the infrared range. Typically,writing on ancient documents appears to the naked eye as black ink on black paper. But when viewed with a multispectral imaging camera, the difference between ink and paper is more distinct because of how differently ink and paper reflect infrared light.


Multispectral imaging is being used in agriculture to manage crops, soil, fertilizing and irrigation more effectively. Multispectral cameras mounted under agricultural drones detectgreen, red, redand near infrared wavebands to capture visible and invisible images of crops and vegetation. Multispectral imaging helps farmers minimize the use of sprays, fertilizers and irrigation, while increasing the yield from their fields.


Farmers integrate their multispectral images with specialized agriculture software that translates the images into meaningful data.This data includes information about land telemetry, soil condition and crop progress, and helps the farmer to monitor, plan and manage the farm more effectively, which saves time and money, and reduces the use of pesticides.


The earliest and most successful uses of multispectral imaging were in diagnostic medicine. Multispectral imaging lets healthcare providers pinpoint the presence of diseases that are hard to identify with other means. Eventually, multispectral imaging was combined with nanotechnology to diagnose health issues at the level of individual cells.


Light interacts with biological tissue in different ways, depending on the wavelength of the light. This makes spectral multispectral imaging a powerful tool for biomedical and chemical applications. For example, images captured in the near infrared wavelength help doctors take depth measurements in tissue and blood chromophores such as oxy-hemoglobin, deoxy-hemoglobin and bilirubin. Spectral imaging has the added benefit of being non-invasive, which makes it useful in assessing burns and skin inflammation. 041b061a72


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