I was wondering if anyone can comment on this excerpt:
"Radiometric resolution of the sensor varies with the amount of energy received at the sensor. Fine spatial resolution requires a small IFOV. Smaller the IFOV, smaller would be the area of the ground resolution cell and hence less energy is received from that area. When the energy received is less, lesser would be the ability of the sensor to detect the fine energy differences, thereby leading to poor radiometric resolution." taken from http://nptel.ac.in/courses/105108077/module2/lecture8.pdf
My knowledge of radiometric resolution is that it reflects the quantization levels of a remote sensing system. I assume that this is independent spatial resolution since gray tone levels are designed with the sensor in mind and not dependent of the reflective properties of the spatial footprint on the ground after the fact. I just can grasp the connection in the excerpt as with other similar but very few instances. I have also not found any of these instances from journal papers or books. Please comment.
Spatial resolution is defined by the IFOV and the altitude of the sensor (which is fixed with the 3 keppler law as soon as you have fixed the period).
THere is always a trade off to find between spatial, radiometric and spectral resolution. HIgh spatial means low IFOV so low radiometric. So if you want relatively high spatial and high radiometric you have to decrease the spectral resolution (which will increse the number of photons as your filter is less restrictive, you lose some colors). This is the case for exemple with the SPOT sensors serie.
Hope it helps
best
hubert
Ron i may say you are not worng but Hubert explained that there is a trade off between the spatial, radiometric and spectral resolution. we cant have best of three is one dataset.
The radiometric resolution of a sensor is not directly defined by the quantization levels. It is defined by the capability of a sensor to discriminate between different values of signal intensity, and as such it is limited fundamentally by the SNR, as it was mentioned by Mr. Liew. It's true that the radiometric resolution may be further degraded by the process of quantising the detected signal (what you are referring to).
Meanwhile, the radiometric resolution can be increased at the expense of either spatial resolution (i.e. when the signal is acquired from a larger area / IFOV) or spectral resolution (which requires a wider spectral bandwidth).
If you speak of signal to noise ratio, indeed spatial resolution have a dramatic impact. If you are limited by the detector noise, noise is constant per pixel. Hence, for the same optics, signal will drop at the second power of the resolution at a constant integration time. However, in remote sensing application, integration time drop must decrease proportionally with the ground resolution to avoid smearing. Hence, when you are limited by the detector noise signal to noise ratio decrease at the third power of the ground resolution for the same optics! It is better if you are shot noise limited.
Thank you all for your responses. It was troubling at first to understand but it definitely makes sense now.
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