Imaging Spectrometer Vs Multispectral Data

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05-02-2011 03:55 PM
BradleyHollamby
New Contributor
Hi all, I am trying to understand the difference between Imaging Spectrometer Data and Multispectral Data.

Could anyone help me?

Thank you in advance!

-Brad
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3 Replies
BradleyHollamby
New Contributor
Okay I think I figured this out:

Multispectral Data has a discrete spectral bands while Imaging Spectrometer data (also refered to as hyperspectral) has a continuous spectrum.

Does this make sense?

Thank You
Brad
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JeffreyEvans
Occasional Contributor III
Brad,
No this is not entirely correct. Unless you are referring to a lab-based image spectrometer (does collect a continuous spectrum), these terms merely refer to multispectral and hyperspectrial sensors, which are the more common terminologies. Hyperspectrial is not continuous, it just has narrow spectral ranges compared to multispectral sensors. This in combination with a very large number of bands, allows for much higher spectral resolution. But keep in mind that there is also quite a bit more noise and the SNR (signal to noise ratio) can make classification more challenging than with multispectral data.

It is critical that you atmospherically correct hyperspectrial data to remove noise attributed to water vapor and scattering. This is not trivial and requires special software (i.e., MODTRAN, ATCOR, ACORN, FLAASH). Whereas, atmospheric correction of multispectral data is considerabley easier with existing models available in both ERDAS and ENVI.

When hyperspectrial data is brought up as a suggestion in a project, I always ask if the question at hand really supports the processing overhead and expense. Rarely is this is the case and usually multispectral is more than adequate, especially given the increasing spatial resolution of many multispectral sensors. If you have a difficult to detect target or one occurring below the pixel level and want to apply a spectral unmixing approach, hyperspectrial may be a good choice.
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BradleyHollamby
New Contributor
Brad,
No this is not entirely correct. Unless you are referring to a lab-based image spectrometer (does collect a continuous spectrum), these terms merely refer to multispectral and hyperspectrial sensors, which are the more common terminologies. Hyperspectrial is not continuous, it just has narrow spectral ranges compared to multispectral sensors. This in combination with a very large number of bands, allows for much higher spectral resolution. But keep in mind that there is also quite a bit more noise and the SNR (signal to noise ratio) can make classification more challenging than with multispectral data.

It is critical that you atmospherically correct hyperspectrial data to remove noise attributed to water vapor and scattering. This is not trivial and requires special software (i.e., MODTRAN, ATCOR, ACORN, FLAASH). Whereas, atmospheric correction of multispectral data is considerabley easier with existing models available in both ERDAS and ENVI.

When hyperspectrial data is brought up as a suggestion in a project, I always ask if the question at hand really supports the processing overhead and expense. Rarely is this is the case and usually multispectral is more than adequate, especially given the increasing spatial resolution of many multispectral sensors. If you have a difficult to detect target or one occurring below the pixel level and want to apply a spectral unmixing approach, hyperspectrial may be a good choice.


Okay so if I understood that all correctly, hyperspectrial data has a higher resolution, due to the great number of bands, but takes considerably more work to prepare the data. And multispectral data is a little less in terms of resolution but is easier to prepare.

Does that basically sum up your response, more correct than my original post?

I apologize for my ignorance I'm just starting into this field.

Thank You!!!
Brad
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