Conversion between radiance and apparent reflectance

DN value

Is the image gray value

Radiance

A little

Apparent reflectance

The reflectivity of the top of the atmosphere

Conversion formula

DN Value to radiance ：
$$L_{\lambda }=Gain\ast DN+Offset$$
In style ,$L_{\lambda }$ Is the equivalent radiance at the entrance pupil of the satellite load channel , Unit is $W/(m^2\ast sr\ast \mu m)$, Gain and offset They are the calibration coefficient gain offset , Company $W/(m^2\ast sr\ast \mu m)$

Radiance to apparent reflectance ：

• $L_{\lambda }$ ditto
• $d$ Is the distance between the sun and the earth , Celestial unit
• $ESU{N}_{\lambda }$ Is the solar irradiance .
• $\theta$ Is the solar altitude angle , And the zenith angle of the sun , If the zenith angle of the sun is known , here $sin\theta$ It can be replaced by $cos\theta$
• All the required parameters above can be passed through the following Other information Link to get

2021521 Update and supplement ：
landsat There are thermal infrared bands in the satellite , So it can be used to retrieve the temperature .

Brightness, temperature

When the radiance of an object is the same as that of a blackbody , The physical temperature of the blackbody is called the brightness temperature of the object . Brightness temperature has the dimension of temperature , But it has no physical meaning of temperature .（ Source theorem remote sensing ： Idea and algorithm ）

Landsat Satellite description , The formula for converting radiance into brightness temperature is given ：

$$T=\frac{K2}{ln\left(\frac{K1}{L_{\lambda }}+1\right)}$$

In style ：
$T$ Is the brightness temperature at the top of the atmosphere
$L_{\lambda }$ Is the radiance at the top of the atmosphere , Company $W/(m^2\cdot sr\cdot \mu m)$
$K1,K2$ Is the conversion constant ,L8 You can find in the header file , Other partial parameters are as follows ：

Other information

• Calibration coefficient issued by China Resources Satellite Application Center 、 Spectral response function and spectral solar irradiance ：http://www.cresda.com/CN/Downloads/dbcs/index.shtml
• USGS Daily distance between the sun and the earth （ Astronomical unit ）：Earth-Sun Distance in Astronomical Units for Days of the Year
• The date corresponds to the day of the year ：DAY OF YEAR CALENDAR

Supplement relevant information

ENVI_IDL The palace of technology is about digital quantification Digital Number, Radiance Radiance, Reflectivity Reflectance, Emissivity Emissive：
http://blog.sina.com.cn/s/blog_764b1e9d0101c7e6.html
Landsat8 data users handbook：
https://www.usgs.gov/media/files/landsat-8-data-users-handbook
Landsat7 data users handbook：
https://www.usgs.gov/media/files/landsat-7-data-users-handbook