You can get the answer at http://landsat.usgs.gov/Landsat8_Using_Product.php, in the metadata file (*_MTL.txt) are the values of gain and offset (REFLECTANCE_MULT_BAND_XX, REFLECTANCE_ADD_BAND_XX)

There are a series of pieces of information you'll need to get to top of atmosphere reflectance. Software like LEDAPS provides many of the necessary pieces i.e. sun-sensor geometry etc. You'll also need the gain and offset for LDCM, which, to the best of my knowledge, hasn't been released yet.

Keep an eye on www.landsat.usgs.gov website for the release of the LDCM gain and offset characteristics.

You can get the answer at http://landsat.usgs.gov/Landsat8_Using_Product.php, in the metadata file (*_MTL.txt) are the values of gain and offset (REFLECTANCE_MULT_BAND_XX, REFLECTANCE_ADD_BAND_XX)

What about E-SUN values of the exatmospheric bands of Landsat 8? Are they available? There is any equation that we can use to estimate them?

You can calculate reflectance direclty ρλ' = MρQcal + Aρ and then divide the result by cos(θSZ) (cosine of sun zenith angle). Or you can assess exatmospheric irradiance applying spectral response functions to solar spectral Irradiance (weighted average).

Dear Hanqiu Xu! As, Luis Palacios mentioned the website, it is mentioned there how to calculate it. At-sensor Reflectance and TOA reflectance are same things.

Thanks for the previus answer!

In order to apply an Atmosperic Correction such as Dark Object Subtraction I follow the same process as Landsat 7? Is there any new method for Landsat 8?

You may have to use this at this stage and wait to see if there is any suggestion in the coming Landsat 8 handbook.

Stella, You can apply dark object subtraction, because it is independent of other factors. But be careful because the bands are not exactly the same. For example in the NIR band the effect of water vapor is much lower in OLI than in ETM+ so it is different transmissivity. Look at: http://landsat.usgs.gov/ldcm_vs_previous.php

@Stella: What is your exact goal to calculate from Landsat8?

I am using Landsat images in order to calculate NDVI and then with an algorithm that uses NDVI and Land use-Land Cover I estimate the Leaf Area Index.

Then you can use the method mentioned here http://landsat.usgs.gov/Landsat8_Using_Product.php. I also used the same. ut don't use bands 1 and 9.

starting from DN gain and offset aren't RADIANCE_MULT_BAND_ and RADIANCE_ADD_BAND_?

GIS Ag Maps has provided a method to do image-based atmospheric correction for Landsat 8. Please visit http://www.gisagmaps.com/landsat-8-atco/. ESUN values were calculated and listed in the Landsat 8 ESUN Values section of the web.

Nevertheless, USGS has indicated “the ESUN values are not provided for Landsat 8 data because they are not required for converting data to reflectance.” So we may have to wait the coming Landsat 8 Handbook to get details regarding the ESUN.

Then what is the role of ESUN values calculated by gisagmaps? If USGS said ESUN values are not required for surface reflectance, then how to get accurate surface reflectance by eliminating atmospheric effects? How we will fit gisagmaps in this domain?

As far as I am aware, ESUN is not designed specially for Atmospheric correction.

http://landsat.usgs.gov/Landsat8_Using_Product.php

In this link from USGS it's possible to read how to calibrate

We are offering an excellent forum for this type of discussions. Why not attending ForestSat 2014? Deadline for abstracts on April 30th, visit http://forestsat2014.com

I have a problem with TOA reflectance with a correction for the sun angle, because when I have SUN_ELEVATION more than 50º my reflectance shows negative values, why? Thank you very much. 

Someone can tell me where I get the Qcal value to calculate the reflectance?

from head file of the image

Dear Hanqiu Xu,

Please find the below link you can get answer. First you have convert DN to Radiance ,then radiance to reflectance conversion is possible.

http://www.rsgis.ait.ac.th/~honda/textbooks/advrs/DN2Reflectance_2p.pdf

Normalization of Landsat 8 bands?

If you use R there is a package called landsat8

Thanks all for the response. The problem now can be worked out as USGS has issued a handbook for this.

Conversion to TOA Radiance

Landsat Level-1 data can be converted to TOA spectral radiance using the radiance rescaling factors in the MTL file:

Lλ = MLQcal + AL

where:Lλ = TOA spectral radiance (Watts/( m2 * srad * μm))ML =Band-specific multiplicative rescaling factor from the metadata (RADIANCE_MULT_BAND_x, where x is the band number)AL=Band-specific additive rescaling factor from the metadata (RADIANCE_ADD_BAND_x, where x is the band number)Qcal =  Quantized and calibrated standard product pixel values (DN)         

Conversion to TOA Reflectance

Reflective band DN’s can be converted to TOA reflectance using the rescaling coefficients in the MTL file:  

ρλ' = MρQcal + Aρ

where:ρλ' = TOA planetary reflectance, without correction for solar angle.  Note that ρλ' does not contain a correction for the sun angle.Mρ=Band-specific multiplicative rescaling factor from the metadata (REFLECTANCE_MULT_BAND_x, where x is the band number)Aρ =Band-specific additive rescaling factor from the metadata (REFLECTANCE_ADD_BAND_x, where x is the band number)Qcal =  Quantized and calibrated standard product pixel values (DN) TOA reflectance with a correction for the sun angle is then: 📷where:ρλ=  TOA planetary reflectanceθSE =  Local sun elevation angle. The scene center sun elevation angle in degrees is provided in the metadata (SUN_ELEVATION).θSZ =Local solar zenith angle;  θSZ = 90° - θSE