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HTC

NDVI of Landsat ETM

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HTC    58

Hello every body!

When i calculate NDVI index of Landsat ETM image. I use function:

NDVI = (IR-RED)/(IR+RED).

The result is not exactly. The NDVI of Rich forest = 0.2-0.3. Infact NDVI of Rich forest >0.5. I use Erdas, Envi... for calculation but the result is bad. The data of mine: Landsat ETM 2003.

If someone know solution, please help me. Thank you very much.

Regard

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HTC    58

These literature research about forest in my country. When i calculate NDVI index in my Landsat image, the result is bad. Value index is low: 0.2-0.3. The rich tropical forest have high value of NDVI (usually: >0.5).

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rahmansunbeam    473

Ok, it's really hard to say anything from this end coz you are the one doing all the literature survey. There could be hundreds of reason why the result do not match

-the source you are talking about has different methodology with different data in different software,

-the data you are using is over or under prepared

-the area you are calling 'rich forest' has changed during this time

-and many more

If I were you, i'd go visit those places called 'rich' and see if the there is really something. That's actually ground truthing.

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dr_s1ngh    15

Dear HTC!! You should first do atmospheric correction of your satellite image using Envi FLAASH or ERDAS ATCOR module.TOA radiance or reflectance would also serve ur purpose. But for getting accurate values of NDVI, you should use reflectance image calibrated by FLAASH module. if U r using ENVI for NDVI calculation using reflectance image.. u should just write the NDVI formula in Band math as:

(((float(b1)-float(b2))/(float(b1)+float(b2))))

where, b1 denotes NIR and b2 represents Red band.

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