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Sensor Accuracy
Posted by EO College on September 30, 2021 at 3:19 pmElina Kreuzberg replied 1 year, 7 months ago 5 Members · 6 Replies 
6 Replies

I think the values in the answer sheet are wrong and dont correspond to the values based on the graphs we get.
For eg, GGreen band , DN is 310, observed value is 0.45. But using the eqn 0.1697*B4 – 7.2858, the value obtained is 45.5212 using the formula, but the value in the answer sheet is 0.456. Also the final spectral signature graph contains values between 0 and 60 whereas in the answer sheet, the values are between 0 and 1. Correction needs to be made. Please clarify if I am getting something wrong

Hi Akash,
Thanks for noticing this. The values are correct, the issues are in the equations. They are missing two decimal points, so for Green it should be 0.001697x – 0.0728 … The equations don’t get automatically updated using your new values, but you can update them yourself with the LINEST equation where y values = reflectance (R) values, and x values = pixel value (DN)
In the meantime, we will update the graphs and correct the equations.
You can still use the graph to check your values by manually looking at the DN and then finding the corresponding reflectance.
Hope that answers your question, and good luck with the rest of the exercise!
Cheers,
Elina

Dear Akash,
thank you for your message.
The responsible authors of the Sensor Accuracy topic will try to get back to you as soon as possible.
Thanks and kind regards,
the EO College Team


Dear Martin,
Thank you for pointing out the bugs! I’ve fixed the broken link and adjusted the values for the different bands, so all should now work!
Best of luck with the rest of the exercise.
Cheers,
Elina
 This reply was modified 1 year, 8 months ago by Elina Kreuzberg. Reason: typo

Dear colleagues,
thank you very much for this interesting lesson. I like the idea of the practical exercise at the end, however, there seems to be an issue with the first step already (exploring reflectances).
Hovering over the different bands gives me the same digital number for each image per target.
For the other option, opening the image in a new tab or window, the link for the red image seems to be broken. Green and NIR work.
Could you please check on this?
Currently, I believe it is not possible to work through the exercise with this errors.
Thank you.
Best regards,
Martin

Dear Martin,
thank you for your feedback.I have contacted the team responsible for the tutorial and we will try to provide you with a timely response.
Thanks,
EO College team

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