[GRASS-user] Low reflectance values with i.atcorr and Landsat 8

GRASS GRASS user
1

Hi,

I am using i.landsat.toar and i.atcorr –r for a region in Germany. The problem I face is that the resulting reflectance values are very low (0.2-0.3 for vegetation in band 5). I think the values should be higher (around 0.6).

I am using Landsat 8 images from Ocotber and from August. For both months I get that low values.

For i.atcorr –r I used an input range of 0,1 and an output range of 0,1. Any idea what I am doing wrong?

Overall the shapes of the reflectance curves for vegetation (value vs bands) seem reasonable, I am just worried about the values which seem to be too low.

i.landsat.toar input=“LC81960252013275LGN00_B” output=“10_toar_B” me\ |

| tfile="C:\Users\lj\Documents\grassdata\LC81960252013275LGN00_MTL.txt\ |

| " sensor=“oli8” method=“uncorrected” percent=0.01 pixel=1000 rayleig\ |

| h=0.0 scale=1.0

i.atcorr -r input=“10_toar_B5@l” range=0,1 parameters="C:\Users\lj\D\ |

| ocuments\grassdata\AC\6S parameters\10_i.atcorr_B5.txt" output="10_a\ |

| tcorr_B5" rescale=0,1

Regards, Lisa.

2
···

Hi Lisa:
Recently I made a set of ToA reflectance and radiance and atmospheric correction, similarly to what you are doing. I chose for the “range=” parameter values that were a bit above and below the min/max DN of all of the images. I first checked with r.info -r for all the bands to get the range of values, and used those to set the range appropriately.
If you try this, let us know if you are satisfied with the results.

Best,
Micha

On 6/15/2015 11:33 AM, John, Lisa wrote:

Hi,

I am using i.landsat.toar and i.atcorr –r for a region in Germany. The problem I face is that the resulting reflectance values are very low (0.2-0.3 for vegetation in band 5). I think the values should be higher (around 0.6).

I am using Landsat 8 images from Ocotber and from August. For both months I get that low values.

For i.atcorr –r I used an input range of 0,1 and an output range of 0,1. Any idea what I am doing wrong?

Overall the shapes of the reflectance curves for vegetation (value vs bands) seem reasonable, I am just worried about the values which seem to be too low.

i.landsat.toar input=“LC81960252013275LGN00_B” output=“10_toar_B” me\ |

| tfile="C:\Users\lj\Documents\grassdata\LC81960252013275LGN00_MTL.txt\ |

| " sensor=“oli8” method=“uncorrected” percent=0.01 pixel=1000 rayleig\ |

| h=0.0 scale=1.0

i.atcorr -r input=“10_toar_B5@l” range=0,1 parameters="C:\Users\lj\D\ |

| ocuments\grassdata\AC\6S parameters\10_i.atcorr_B5.txt" output="10_a\ |

| tcorr_B5" rescale=0,1

Regards, Lisa.

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