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Catégorie :Category: nCreator TI-Nspire
Auteur Author: cami.cd
Type : Classeur 3.0.1
Page(s) : 1
Taille Size: 5.34 Ko KB
Mis en ligne Uploaded: 29/01/2025 - 01:00:13
Mis à jour Updated: 29/01/2025 - 01:00:21
Uploadeur Uploader: cami.cd (Profil)
Téléchargements Downloads: 2
Visibilité Visibility: Archive publique
Shortlink : http://ti-pla.net/a4482996
Type : Classeur 3.0.1
Page(s) : 1
Taille Size: 5.34 Ko KB
Mis en ligne Uploaded: 29/01/2025 - 01:00:13
Mis à jour Updated: 29/01/2025 - 01:00:21
Uploadeur Uploader: cami.cd (Profil)
Téléchargements Downloads: 2
Visibilité Visibility: Archive publique
Shortlink : http://ti-pla.net/a4482996
Description
Fichier Nspire généré sur TI-Planet.org.
Compatible OS 3.0 et ultérieurs.
<<
PhotogrammetryRemote Sensing (PG1-PRS) 5 Sensors The electromagnetic spectrum We already talked about the electromagnetic spectrum and identified those parts that are relevant to remote sensing activities: Ï Visible light (true color imaging) Ï Infrared (spectral information and thermal radiation) Ï (near-)UV (spectral information) Ï Microwaves (radar applications) We will focus here on the first three wavelength regions, as they are relevant to most (passive) imaging activities. Thus, the sensors to observe in these regimes are very similar and are typically based on either CCD or CMOS detectors. CCD and CMOS detectors CCD and CMOS detectors consist of semi conductor-based pixel arrays that are photosensitive. Incoming photons release electrons, which are initially trapped in potential wells. While CCDs are read out column-wise using row-wise amplifiers, CMOS pixels can all be read out at the same time using pixel-wise amplifiers. CCD and CMOS detectors are the defacto standard for digital imaging applications as they provide excellent linearity (between the number of incoming photons and the pixel read-out values) over much of their dynamic range. CCDs typically tend to have a higher dynamic range than CMOS detectors, as well as higher sensitivity and lower noise. This makes CCD detectors a first choice for scientific instruments. But, in order to reach these superior qualities, these detector have to be actively cooled (e.g., using liquid nitrogen). CMOS detectors still provide very good dynamic range, sensitivity and noise properties, but they are significantly cheaper and can be used without active cooling. In the end, both CCD and CMOS detectors can be (and are being) used for the same applications. Spectral sensitivity Depending on the setup of the detectors, there are differences in spectral sensitivity. Here is a comparison of a CCD and CMOS detector, both using R, G and B filters. Excessive transmission in the near-infrared is also possible in CCD sensors. Spectral sensitivity - Infrared As we will see in the following, some detectors are specifically designed to be sensitive to infrared wavelengths, as shown here. Different combinations of semiconductor materials provide different sensitivity properties and enable observations over a wide spectral region. Spectral Imaging By default, CMOS (and other) sensors only count the number photons absorbed, but have no information on the color (energy) of the absorbed photons. How do we receive color information? We have to employ bandpass filters (multispectral imaging) that only allow photons of a specific wavelength range to pass before they reach the sensor array. Example Instruments In the following, we will have a quick look at some existing devices for different imaging techniques and sensor platforms. Keep an eye on how the requirements to these detectors drive their design... UAV RGB imaging Zenmuse P1 Use Case: Photogrammetry The Zenmuse P1 integrates a full-frame sensor with interchangeable fixed-focus lenses on a 3-axis stabilized gimbal. Designed for photogrammetry flight missions, it takes efficiency and accuracy to a whole new level. Ï 45 MP Camera Ï f/2.8-f/16 Ï Georeferenced Imagery for High-Accuracy Mapping Ï Light-weight camera with stabilized gimbal UAV RGBI imaging DJI Mavic 3 Use Case: Precision Agriculture Ï 20 MP RGB camera Ï 5 MP multispectral camera (G, R, Red Edge, NIR) Ï Fully integrated into UAV with stabilized gimbal Aerial Imaging Aerial imaging cameras for aircraft use are significantly larger und more powerful (Leica DMC-4, Vexcel) Aerial Imaging: Vexcel Ultracam Dragon 4.1 Professionel hybrid sensor for aerial imaging RGB-NIR imaging sensor with 149 Mpixel, 2cm GSD @ ~2000m altitude, combined nadir und ublique view RIEGL Lidar Scanner: 2,4 Mhz (2 million pulses per second) Satellite multispectral imaging Space-borne instruments must withstand much harsher conditions: they must operate in vacuum, withstand large temperature differences (-10C to 45C for most electronic components) and be built robust enough to stay calibrated after launch. Example: Sentinel-2s Multi Spectral Imager (MSI): 150 mm telescope, 3-mirror design, dichroic beam splitter to separate VNIR from SWIR, the instrument operates in a pushbroom design using line scanners. The Sentinel-2 MSI focal plane consists of 12 individual detectors that are aligned in a staggered formation. This allows the detector array to take advantage of the full 20,6° field of view of the optics and deliver a swath width of 290km on the ground. Each individual VNIR detector (shown here) contains 10 line sensors for 10 different bands. These bands using different GSD of 10m, 20m and 60m (we will discuss Sentinel-2 in detail in a future lecture). The result is a stack of 10 (13 total) images of the same scene. Satellite hyperspectral imaging Requirements for hyperspectral imaging are different than for multispectral imaging. Instead of controlling the spectral respon
[...]
>>
Compatible OS 3.0 et ultérieurs.
<<
PhotogrammetryRemote Sensing (PG1-PRS) 5 Sensors The electromagnetic spectrum We already talked about the electromagnetic spectrum and identified those parts that are relevant to remote sensing activities: Ï Visible light (true color imaging) Ï Infrared (spectral information and thermal radiation) Ï (near-)UV (spectral information) Ï Microwaves (radar applications) We will focus here on the first three wavelength regions, as they are relevant to most (passive) imaging activities. Thus, the sensors to observe in these regimes are very similar and are typically based on either CCD or CMOS detectors. CCD and CMOS detectors CCD and CMOS detectors consist of semi conductor-based pixel arrays that are photosensitive. Incoming photons release electrons, which are initially trapped in potential wells. While CCDs are read out column-wise using row-wise amplifiers, CMOS pixels can all be read out at the same time using pixel-wise amplifiers. CCD and CMOS detectors are the defacto standard for digital imaging applications as they provide excellent linearity (between the number of incoming photons and the pixel read-out values) over much of their dynamic range. CCDs typically tend to have a higher dynamic range than CMOS detectors, as well as higher sensitivity and lower noise. This makes CCD detectors a first choice for scientific instruments. But, in order to reach these superior qualities, these detector have to be actively cooled (e.g., using liquid nitrogen). CMOS detectors still provide very good dynamic range, sensitivity and noise properties, but they are significantly cheaper and can be used without active cooling. In the end, both CCD and CMOS detectors can be (and are being) used for the same applications. Spectral sensitivity Depending on the setup of the detectors, there are differences in spectral sensitivity. Here is a comparison of a CCD and CMOS detector, both using R, G and B filters. Excessive transmission in the near-infrared is also possible in CCD sensors. Spectral sensitivity - Infrared As we will see in the following, some detectors are specifically designed to be sensitive to infrared wavelengths, as shown here. Different combinations of semiconductor materials provide different sensitivity properties and enable observations over a wide spectral region. Spectral Imaging By default, CMOS (and other) sensors only count the number photons absorbed, but have no information on the color (energy) of the absorbed photons. How do we receive color information? We have to employ bandpass filters (multispectral imaging) that only allow photons of a specific wavelength range to pass before they reach the sensor array. Example Instruments In the following, we will have a quick look at some existing devices for different imaging techniques and sensor platforms. Keep an eye on how the requirements to these detectors drive their design... UAV RGB imaging Zenmuse P1 Use Case: Photogrammetry The Zenmuse P1 integrates a full-frame sensor with interchangeable fixed-focus lenses on a 3-axis stabilized gimbal. Designed for photogrammetry flight missions, it takes efficiency and accuracy to a whole new level. Ï 45 MP Camera Ï f/2.8-f/16 Ï Georeferenced Imagery for High-Accuracy Mapping Ï Light-weight camera with stabilized gimbal UAV RGBI imaging DJI Mavic 3 Use Case: Precision Agriculture Ï 20 MP RGB camera Ï 5 MP multispectral camera (G, R, Red Edge, NIR) Ï Fully integrated into UAV with stabilized gimbal Aerial Imaging Aerial imaging cameras for aircraft use are significantly larger und more powerful (Leica DMC-4, Vexcel) Aerial Imaging: Vexcel Ultracam Dragon 4.1 Professionel hybrid sensor for aerial imaging RGB-NIR imaging sensor with 149 Mpixel, 2cm GSD @ ~2000m altitude, combined nadir und ublique view RIEGL Lidar Scanner: 2,4 Mhz (2 million pulses per second) Satellite multispectral imaging Space-borne instruments must withstand much harsher conditions: they must operate in vacuum, withstand large temperature differences (-10C to 45C for most electronic components) and be built robust enough to stay calibrated after launch. Example: Sentinel-2s Multi Spectral Imager (MSI): 150 mm telescope, 3-mirror design, dichroic beam splitter to separate VNIR from SWIR, the instrument operates in a pushbroom design using line scanners. The Sentinel-2 MSI focal plane consists of 12 individual detectors that are aligned in a staggered formation. This allows the detector array to take advantage of the full 20,6° field of view of the optics and deliver a swath width of 290km on the ground. Each individual VNIR detector (shown here) contains 10 line sensors for 10 different bands. These bands using different GSD of 10m, 20m and 60m (we will discuss Sentinel-2 in detail in a future lecture). The result is a stack of 10 (13 total) images of the same scene. Satellite hyperspectral imaging Requirements for hyperspectral imaging are different than for multispectral imaging. Instead of controlling the spectral respon
[...]
>>
