color bar changes?

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Topic Products and Algorithms / Satellite Data Products & Algorithms / color bar changes? (locked) (2105 hits)

By Helga Date 2011-07-22 16:03

Hi,
I had saved several png files of weekly images from 2002 to 2007 that I had generated using the merged chla product when it was available 2 yrs ago. The color bar then defaulted to 0.01 to 64. Yesterday when I extended the series to 2011 so I could compare the rest of the years I noticed that the color bar defaults to 20. I loaded an older image that i could compare to be previously generated png files.
Granted I couldn't use merged product but even so i am seeing two very different images even if if tweak the color settings. I see very high chla in the Gulf of Oman which i dont in the older image - also the feature at the mouth of the Gulf of Oman is so much smaller and less distinct - do you think its just artifacts of size of image, color bar etc?
thanks a lot and apologies if this is trivial!
I am attaching the 2 images.
Helga

Attachment: comparison.pdf (240.9k)

By @sean Date 2011-07-22 19:24

Helga,

The two images - aside from being different in geographical extent - appear to be two different projections.
Both the geographic extent AND the projection are affecting the apparent size of the feature in the Gulf of
Oman. And definitely, the color bar differences as well. The merged image is scaled from 0.01 to 64 mg/m^3
while the Aqua only version is scaled from 0.01 to 20 - You should be able to scale the Aqau only version
to match the 0.01 - 64 range - thus reducing the apparent discrepancy between the two.

Sean

By Helga Date 2011-07-22 20:23

Hi Sean,
Sorry for the bother but i am not sure how i can extend the color LUT - I tried the LUT control window but i am not sure how that works. Do i have to make a new LUT file?
Thanks
Helga

By @sean Date 2011-07-22 22:23

Helga,
In the image display window, use the Functions->Rescale option.
You don't need to change the LUT, just the scaling.
Sean

Topic Products and Algorithms / Satellite Data Products & Algorithms / color bar changes? (locked) (2105 hits)