请问spot-vgt数据中s10与d10有什么区别？sm（status map）数据如何使用？

<P> 在网上查了好久好久，都没能找到答案</P>
<P>很希望能在这里得到高人指点！</P>
<P>非常感谢！！！！</P>

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<P 10px; MARGIN-RIGHT: 10px"><FONT face="Arial, Helvetica, sans-serif" size=2>VGT-S (S= synthesis) products are MVC or Maximum Value Composite Syntheses. The pixels selected for the syntheses are based on the selection of the maximum NDVI value, to ensure coverage of all landmasses worldwide with a minimum effect of cloud cover. The pixel brightness count is the ground area's reflectance (corrected for atmospheric effects); pixels in the sea area are set to 0. A map of computed normalised difference vegetation index values (NDVI image plane) is also supplied with the product.  </FONT>
<P 10px; MARGIN-RIGHT: 10px"><FONT face="Arial, Helvetica, sans-serif" size=2>Each pixel of a VGT-S product represents a ground area of approximately 1 km x 1 km. The global coverage of a synthesis extends from 75°N to 56°S. A VGT-S product can be ordered as a VGT-S1 or a VGT-S10 product, in a map projection specified by the user, covering the whole world or a selected part (region of interest) defined by the user. </FONT></P></FONT>
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<P><FONT face="Arial, Helvetica, sans-serif" size=2>VGT D-10 products are BDC syntheses or BiDirectional Composite syntheses. These syntheses are based on a bidirectional reflectance distribution function.</FONT></P>
<P><FONT face="Arial, Helvetica, sans-serif" size=2>The pixel brightness count is the ground area's reflectance; pixels in the sea area are set to 0.</FONT></P>
<P><FONT face="Arial, Helvetica, sans-serif" size=2>A VGT-D product covers the whole world or a selected part (region of interest) and can be ordered in a map projection specified by the user. The global coverage of a synthesis extends from 75°N to 56°S. A map of computed normalised difference vegetation index values (NDVI image plane) is also supplied with the product.</FONT></P>
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<LI><FONT face="Arial, Helvetica, sans-serif" size=2>The status map of an BDC synthesis includes the following indicators: sea/land, ice-snow/not ice-snow, clouds or shadow/clear, MIR quality, BRDF model adjustment quality flag for each band.</FONT> </LI>