Hi,

The error could be from calculating the reflectance. Maybe your scaling factors were wrong. Did you perform your Atmospheric corrections adequately?

You could also use other GIS softwares to verify your answers.

It will be helpful if you could provide the satellite platform you got your images from.

I have downloaded the image from https://earthexplorer.usgs.gov.

I have just converted DN value to reflectance value using the following formula:

(2.0000E-05 * $n1_lc08_l1tp_137045_20151112_20170402_01_t1_sr_band7)+(-0.100000)

and

$n3_memory / SIN (46.28567539).

I want to add that when I generate the NDVI index, the result is found accurate.

it is same as any software just go through the tool

Thanks for your answer @ Hayder Dibs. I got my solution.

Hi Sushanta Gupta,

You could also download your study area image through ESPA. Good luck.