L8 TOA Reflectance values >1 are probably due to cloudy pixels and values

High TOA reflectance values are also probably due to atmospheric influence (primarily path radiance) hence a proper atmospheric corrections should be applied to TOA reflectance through a suitable  radiative transfer model.

Excellent read and demonstration to understand and analyze Landsat 8 data for many applications:

http://surfaceheat.sites.yale.edu/understanding-landsat-8

enjoy......

Hi,

2.4 is odd. Try another data set or stretch your current TOA data between 0 and 1

Update- I took each band and manually retrieved TOA reflectance using the ρλ = (MρQcal + Aρ)/(sin(θSE)) formula and metadata info per band. I then ended up with values mostly in the 1.2-1.4 range as my maximum values, which is significantly better, and may be attributed to artifacts, cloudy pixels, etc. in the scenes. I then manually corrected for atmosphere using dark subtract for each band separately. This seems to be working much better; thank you all for the input, an I hope my algorithm step also works!

see link meybe help you but its for ENVI 5.3

and the formula he used for band math you can finde in text below

sorry all guys i have a question.

i have some  points data contains x,y (coordinates) and some measured material on the 

ground  by Spectrometer. now i got TOA reflectance using ENVI 5.3.

how can i extract  spectrum value or DN from IMG or TIF and their coordinates be same as points i had?

https://www.youtube.com/watch?v=5Ce0rghyrcU&t=7s

Arshad, regarding your question, I think there are a number of ways to extract DN values of specific points along with its coordinates of a multi-band raster in ENVI 5.3. Refer to the answer that I have added to your question on your profile page.