[GRASS-user] i.atcorr with ASTER L1B

[Michael Perdue]

If you can interpolate and organize the data as follows, I can  
incorporate it fairly painlessly;

/* not real data */
sensor= Spot 2
band= 3 hvr2
Lower edge wavelength = 0.715
Upper edge wavelength = 0.9175
Spectral Response =
.0000, .0001, .0001, .0002, .0004, .0005, .0007, .0009
.0012, .0014, .0017, .0021, .0024, .0028, .0032, .0036
.0040, .0045, .0054, .0065, .0080, .0112, .0170, .0245
.0330, .0450, .0740, .0990, .1520, .2140, .3050, .4200
.5970, .6750, .7900, .8270, .8400, .8408, .9010, .9050
.9100, .9140, .9050, .9260, .9470, .9670, .9760, .9840
.9710, .9790, .9880,1.0000, .9902, .9840, .9780, .9710
.9470, .9510, .9450, .9380, .9340, .9300, .9360, .9420
.9140, .8970, .7980, .7000, .5970, .4610, .3700, .2630
.1730, .1259, .0888, .0619, .0450, .0346, .0267, .0207
.0160, .0120, .0086, .0060, .0040, .0025, .0013, .0003
.0000

Note that;
(Upper edge wavelength - lower edge wavelength)/2.5nm should equal the  
number of elements in the Spectral response.
(Lower edge wavelength - 250nm)/2.5nm should be a integer. ie 250,  
257.5 & 260 not 251,258.5 & 261.

Linear interpolation is probably the safest, but bilinear should be  
fine. I'd plot the "before" and "after" one on top of the other to  
make sure there are no major deviations between the two. If you're  
familiar with, I found using Octave/matlab and interp1 to greatly  
simplify things. In the mean time I'll try to figure out GeomCond.cpp  
so I can simply submit a patch.

Cheers,

Mike

On 28-Jul-09, at 5:23 PM, andrew haywood wrote:

> Hi Mike
>
> thanks for this supporting information. I will start the  
> interpolation. Is there any prefered method for this? Can I use a  
> bilinear approach.
> I think this is as far as I can take it though - as I have no  
> understanding of lwave.cpp and the file construct. Will it be ok to  
> post a txt file on the list with the interpretation results?
>
> Cheers
> Andrew
>
>
> On 7/29/09, Michael Perdue <michael_perdue at yahoo.ca> wrote:
> Hi Andy,
> Yes, it looks like the right info for the SPOT sensor platforms.  
> Iwave.cpp expects the data to be in 2.5nm increments so you will  
> have to interpolate the data to the correct interval. It's a bit  
> tedious, but is straight forward. I might be able to dedicate some  
> time to it, but won't have any till the weekend now.
> Cheers,
> Mike
>
> On 27-Jul-09, at 10:35 PM, andrew haywood wrote:
>
>> Hi All,
>>
>> Im just adding to this discusssion. I would be interested in using  
>> i.atcorr with SPOT 2, 3, 4 and 5. I have found a file on the http://www.spotimage.com/web/en/555-spot-images.php 
>>  website that contains the spectral sensitivity data. Is this the  
>> same as the spectral profile? It looks like the data is in 5nm  
>> increments. Do i need to create 2.5nm increments or can i tell the  
>> function its in 5nm or 10nm increments?
>> Any help would be appreciated.
>> thanks
>> Andy
>>
>>
>>
>> On 7/28/09, Michael Perdue <michael_perdue at yahoo.ca> wrote:
>> Hi Markus,
>>
>> Here is a text file with everything organized as I think it should  
>> be. I didn't add the this Iwave.cpp to submit a patch as I wasn't  
>> really sure how to modify GeomCond.cpp.
>>
>> Cheers,
>> Mike
>>
>> On 26-Jul-09, at 1:34 PM, Markus Neteler wrote:
>>
>> Great - the header of Iwave.cpp contains instructions how to add
>> a new sensor like this.
>>
>> thanks
>> Markus
>>
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>>
>
>
>

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