Hi,
I’m newbie in GRASS GIS and image processing. I want to produce NDVI maps from Landsat 8 imagery. I try to convert Landsat 8 DN to ToAR by using i.landsat.toar module in GRASS GIS v7.0.svn - on Windows 8 x64 platform.
The conversion parameters (Earth-Sun distance, sun elevation, DN range, gain and bias and etc.) are all reported as 0 (zero) in metadata of resulting ToAR maps (I’ve added one of the metadata generated by r.info at the end of my message).
Another issue during the conversion process, i.landsat.toar module warn that
ESUN evaluated from REFLECTANCE_MAXIMUM_BAND
???
r.report stats:
n: 10403
minimum: 0.0227376
maximum: 0.587083
Is there a problem in ‘DN to ToAR conversion’ in GRASS GIS 7.0?
How to resolve this issue? And my last question is: Can I trust these results obtained by i.landsat.toar?
Best regards,
Dr. Hasan Sarptaş
Ege University
Solar Energy Institute
Energy Tech.
İzmir, TURKEY.
(Wed Jan 22 02:49:22 2014)
r.info map=ToA_Ref_4@Landsat
±---------------------------------------------------------------------------+
| Layer: ToA_Ref_4@Landsat Date: Wed Jan 22 02:41:47 2014 |
| Mapset: Landsat Login of Creator: Hasan |
| Location: Ege |
| DataBase: C:\Users\Hasan\Documents\GIS DataBase\Landsat8 |
| Title: ( ToA_Ref_4 ) |
| Timestamp: none |
|---|
| Type of Map: raster Number of Categories: -0 |
| Data Type: DCELL |
| Data Units: unitless Vertical datum: (none) |
| Rows: 7811 |
| Columns: 7671 |
| Total Cells: 59918181 |
| Projection: UTM (zone 0) |
| N: 4423515 S: 4189185 Res: 30 |
| E: 716115 W: 485985 Res: 30 |
| Range of data: min = 0.0154847031183999 max = 2.65962954976276 |
| Data Description: |
| generated by i.landsat.toar |
| Comments: |
| Reflectance of Landsat-8 OLI/TIRS (method uncorrected) |
| ----------------------------------------------------------------- |
| Acquisition date (and time) … 2013-12-05 (-0.0000 h) |
| Production date … 2013-12-05 |
| Earth-sun distance (d) … -0.0000000 |
| Sun elevation (and azimuth) … -0.00000 (0.00000) |
| Digital number (DN) range … 0 to 0 |
| Calibration constants (Lmin to Lmax) … -24740000909121687407621537690 |
| DN to Radiance (gain and bias) … +0.00000 and +0.00000 |
| Mean solar irradiance (ESUN) … 0.000 |
| Radiance to Reflectance (divide by) … +0.00000 |
| ------------------------------------------------------------------ |
| i.landsat.toar input_prefix=“LC81800332013339LGN00_B” output_prefix=\ |
| “ToA_Ref_LC81800332013339LGN00_B” metfile=“LC81800332013339LGN00_MTL.txt” sensor=“oli8” met\ |
| hod=“uncorrected” percent=0.01 pixel=1000 rayleigh=0.0 |
| ±---------------------------------------------------------------------------+ |
| (Wed Jan 22 02:49:23 2014) Command finished (0 sec) |