This thesis describes the work carried out jointly by the University of KwaZulu-Natal and the Council for Scientific and Industrial Research (CS IR), under the supervision of Dr. N.C hetty and co-supervisi on of Dr M.D. First of all, I would like to thank my supervisor Dr N Chet ty and my co-supervisor Dr M.D Lys ko. Dr. S Bernard, the project manager of SWEOS, I am extremely grateful for both your assistance during field tests and the great knowledge given to me.
To Mrs Nobuhl e M ajozi and M r M ark Matthews, I am especially grateful for your help in carrying out measurements during the Loskop field trial.
Int roduction
The atmospheric path that separates the water body and the satellite, in addition to the land masses adjacent to the water body, affects the interpretation of the signal received by the satellite sensors or. Satellite-derived optical products need to be validated with real in situ water data to test the effectiveness of radiative transfer algorithms. The confidence of the validation process increases as the number of validation sites increases, especially for turbid water ecosystems where the optical behavior of water has significant variations.
Ship-based on-site validation offers spatial coverage that can increase confidence in validation processes. Finally, in addition to the intended elite validation capability, the realized network of H yDROWs can be used as an early warning system for bloom detection and an aquatic monitoring system.
Res earch S trat egy
Radi ometr y of HAB det ection
- Solid angle
- Radi ance
- Irradi ance
- Spectral Region of Interest
Analogously to spec tral radiation, the spec tral i radi ance i s i radi ance of a differential wavelength interval h i nterval dλ, centered on a s peci fi c wavelength is gi ven b y. Figure 6 is a poor report of solution irradiance at the opp of the atmosphere (TOA) and at the Earth's surface. The natural structure of water makes it a strong absorber of red and infrared light, thus setting a realistic upper limit of 750 nm.
Absorpt ion and s cat eri ng characteristics of certain particles act as a unique signature, often helping to determine the type of substance present in the water mass and its relative concentration. . The absorpt ion bands cause a drop in photon count at the wavelengths of absorption.
Upwell ing radi ance i n ret ri eving s at ellit e rem ot e s ensed dat a
Summar y
As a result, two possible spectral cores were experimentally investigated with the aim of including the most powerful detector in the prototype radiometric device. To test the performance of the prototype instrument in a disturbance-free environment, it was taken to the Los kop dam in the Mpumalanga province of South Africa. Measurements were made with H yDROW and the reference radiometer, H yperTSRB, at 5 optically dynamic sites.
This helped to conclude an unbiased performance assessment of the first rum graft. This second prototype will be deployed for a two-month period at S aldanha Bay on South Africa's west coast with the aim of evaluating its performance relative to a TriOS radiometer.
Sataylayt haypaspɛktral rimot sɛns fɔ ɛstiurin ɛn kɔstal wata kwaliti ɛstimɛshɔn. Intapriteshɔn fɔ haypaspɛktral rimot sɛns imej dɛn bay spɛktrum maching ɛn lukɔp tebul dɛn.
High water temperatures and nutation rates, together with projected climate changes are expected to result in an increase in the frequency and susceptibility of cation-li eutrophic blooms.1. The devastating impact of such phenomena on freshwater and freshwater systems threatens aquaculture, agriculture and the tourism industry on a global scale. ys t ems (SWEOS) proposes the use of space-based techniques combined with radiomet in-situ ric t echnol ogy to provide a robust and cost-effective method of address ng al gal bloom rel and ed haz ards. The actions that follow here give an overview of the decisions made in choosing the sensor that will be for us based on the radio and others. The SWEOS project is a m ulti-disciplinary initiative to address the severe impact of HABs on water resources in Southern Africa as Oberholster and Ashton document.1 4 Combining the emblematic project of new technol ogy with a sustainable, cost-effective and unconditional technology.
The light-sensitive pixels absorb incident photos and release electrons through the photoelectric effect.2 0 The accumulation of charge over the exposure time is transferred and converted into an analog volt age which is then converted into a digital number. The influence that optics has on the fate of light entering the system is illustrated in Figure 1 for C1 and C2.2.1 The optical design of C2 takes a more conventional shape approach where the light enters through a constraint. The part of the electromagnetic spectrum relevant for most measuring applications in water ranges from 400 nm to 750 nm.
These resolutions are considered to be sufficient to capture the upwelling radiance in water, which usually exhibits distinct signatures devoid of harp features, as seen in work by Ramkil owan and Chett y2, Di errs en and Kudel a7, and Kohl er and Philpot .2 2 The improved resolution (b y 2 nm ) that C2 has over C 1 is evident for this application. As a result, the performance of the prototype radiometer would be compromised. Facts that were considered but compromised in terms of instrument temperature stability, capacity to obtain dark signal measurements and correction for stra y light.
Stra y li ght pl a ys a major role in the non-immediate behavior of radiom e new modul e candidate c. The disadvantage of minimal traj y ive corrections (if an y) that are provided by the manufacturer is reasonable enabled by an experimental behavior conducted by y R am kil owan and Chett y.2. A workhorse dependent on the function of the instrument forces all that the dark signal to be characterized as a function of its function, all because the dark signal may be necessary manual. data capture.
C1, the cheaper of the two spectrom eters produced superior or SNR, optical throughput and spec tral sensitivity results making it the preferred candidate for us in the development of the prot ot ype radiom et er. Moreover, the correlation between H yDROW and the reference is greater than 0.99 for most of the sites.
The development of affordable bio-optical sensors is an invaluable aspect of the project. The usual approach and approach in the laboratory to calibrate radiometers is with a calibrated radio together with a uniform and well-defined light source that has a good spectral balance with respect to the characteristic response of the i nst rum ent. Five sampling locations were selected along the length of the dam as shown in Figure g.
The custom exposure time for H yDROW was chosen to be within 1 ms of the optimized exposure time set by HyperTSRB. When a light detection device is used in a medium other than that in which it was calibrated, the change in the refractive index of the intervening medium (in this case water) will cause changes in the absolute spectral response. An immersion factor or If is used to compensate for the difference in response to the instrument.
First, the refractive index at the glass-air interface (during calibration) differs from the refractive index of the glass-water interface (during in-water measurements. Second, when immersed in water, the instrument's field of view solid angle is reduced, so that a smaller percentage of the radiation can be detected. Here is the refractive index of the water and ng is the refractive index of the glass window of the i nst rum ent.
Although nw will likely differ from the actual refractive index of the water, its consistent use for both instruments reduces the relative error. It is not the case that the average self-deviation errors for the upwelling radiation from the H yperTSR B are approximately 5% (Leathers et al., 2001). The upwelling radiation signature is captured as an image of the entrance slit on the detector array.
Ideally, the image should be consistent with the spectral components of the target within the instrument bands. This can be done after recalibrating the H yperTSR B and with the data processed with ProSoft 8.0.
