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Short answer
Different plants reflect light at different wavelengths with specific patterns. If you know the reflection pattern of a broad-leaved forest and that of a needle-leaved forest, you can compare them with the pattern observed with a satellite and conclude to which forest it is more similar.
Long answer
Optical remote sensing
Optical sensors ...
5
In general, no, NDVI is not used to derive vegetation type. NDVI is useful for studying phenology, but it won't tell you the type of plant that is being remotely sensed. Good land cover systems use a variety of data sources to derive general plant type (e.g. conifer vs deciduous). For instance, the National Land Class Database (NLCD) description states:
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Most likely, climatology means there was no retrieval at all.
Bayesian retrievals combine information from an a priori with information from measurements. When the retrieval fails for whatever reason, or the measurement contains insufficient information, instead of reporting no measurement at all, they copy over information from the a priori and use the ...
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Gerrit is correct, the climatological setting indicates that the value is filled in (not an actual retrieval). If you see the MODIS Vegetation Index User’s Guide, it is discussed a few times:
Cloud-free global coverage is achieved by replacing clouds with the historical MODIS time series climatology record (Fig. 5)
and
In the Climatology Fill case, ...
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After given some information about the data source I have a simple answer. Since the underscores SW etc. represent the four pixels around the city center and all the pixels cover the same physical area, taking a mean of the values will represent the average NDVI of the total area.
It is all about what you will do with the NDVI data. E.g. if something ...
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