Ratiometric dating

However, this reduces the amount of energy that can be detected as the area of the ground resolution cell within the IFOV becomes smaller.This leads to reduced radiometric resolution - the ability to detect fine energy differences.The radiometric resolution of an imaging system describes its ability to discriminate very slight differences in energy The finer the radiometric resolution of a sensor, the more sensitive it is to detecting small differences in reflected or emitted energy. The illustration on the right is the same but presented in 8 bits or 256 shades of grey, which provides more details.This collage shows the difference in the level of detail between the two representations.

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Here researchers showed that Zircons can form in the upper mantle and persist there for millions of years before entering the Earth's crust through volcanic processes.Image data are generally displayed in a range of grey tones, with black representing a digital number of 0 and white representing the maximum value (for example, 255 in 8-bit data).By comparing a 2-bit image with an 8-bit image, we can see that there is a large difference in the level of detail discernible depending on their radiometric resolutions.Zircons can be found in igneous rocks, metamorphic rocks and also in sedimentary deposits. A typical zircon crystal in granite for example is 100 - 300 micrometers across, although some can grow to several centimetres in size - especially in pegmatites (a very coarse-grained rock similar in composition to granite).Another interesting property of Zircon is its durability.Conversely, coarser spatial resolution would allow improved radiometric and/or spectral resolution.Thus, these three types of resolution must be balanced against the desired capabilities and objectives of the sensor.However, if only 4 bits were used, then only 24=16 values ranging from 0 to 15 would be available.Thus, the radiometric resolution would be much less.Imagery data are represented by positive digital numbers which vary from 0 to (one less than) a selected power of 2. The maximum number of brightness levels available depends on the number of bits used in representing the energy recorded.This range corresponds to the number of bits used for coding numbers in binary format. Thus, if a sensor used 8 bits to record the data, there would be 28=256 digital values available, ranging from 0 to 255.

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