Statistics in SNAP

snap
#1

Hello guys,

Sorry for a simple question. But I really don’t get it statistics and histogram in SNAP. I’ve downloaded the landsat 8 product level 2, which should be atmospherically corrected and with surface reflectance values, but valus on x-axis are still in Digital Numbers probably? I’ve tried open it in ENVI at university and ENVI is also describing values in tables (compute statistics in ROIs) as DN.

Can anyone explain me a principle behind this? Thx

#2

Hi Lukáš,

USGS stores DN in the GeoTiff files of Landsat 8. In the *_MTL.txt are conversion factors to radiances and reflectances stored.
If you use the MTL.txt file to open the L8 data you will get the radiances. There is a property which lets you switch to reflectances.

If not present, create a file ‘s3tbx.properties’ in the folder [USER_HOME]/.snap/etc
in this file ‘s3tbx.properties’ add the entry

s3tbx.landsat.readAs=reflectance

If you open the GeoTiff files individually you will get the DN values.

Radiometric correction
Landsat 5/8 LVL1 Products Calibration with SNAP?
#3

Thank you Marpet I’ve already find the answer… the measure is surface reflectance but units are in binary code because it is easier for processing!