Water detection

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Water detection

sander.z
Hello,

My name is Sander and i'm a practical trainee at a compagnie in the Netherlands. One of my projects is to (automatically) detect water in satellite photos for use in GIS projects. I have read the manual but i cant figure out how do do this on a single TIFF image. What do i have to do? Do i need more than one file? I'm new to this.

I got is a TIFF true color image and a TIFF infrared image.

Thank you!
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Re: Water detection

Bas Retsios
Hi!

I would try the NDVI / NDWI method, thus compute an image with those
formulas and see if you can detect which pixels contain water based on a
threshold that you will have to find.

Please have a look here:
ftp://ftp.itc.nl/pub/ilwis/ilwis30/pdf/chap06.pdf
You can jump directly to chapter 6.5.2 "Normalized Difference Vegetation
Index" on page 250 (the PDF starts at page 209)

Check here for the generic NDVI formula (Normalized Difference
Vegetation Index):
http://en.wikipedia.org/wiki/Normalized_Difference_Vegetation_Index
And here for the NDWI formula (Normalized Difference Water Index):
http://www.seos-project.eu/modules/agriculture/agriculture-c01-s03.html

The problem may be that the images that are provided to you do not
exactly match the required input for the formulas, but you can still try
it and check if you get a good result.

ILWIS list: if someone has a better suggestion, please submit here.

Cheers,

Bas Retsios
ILWIS team


On 11/3/2015 11:58, sander.z wrote:

> Hello,
>
> My name is Sander and i'm a practical trainee at a compagnie in the
> Netherlands. One of my projects is to (automatically) detect water in
> satellite photos for use in GIS projects. I have read the manual but i cant
> figure out how do do this on a single TIFF image. What do i have to do? Do i
> need more than one file? I'm new to this.
>
> I got is a TIFF true color image and a TIFF infrared image.
>
> Thank you!
>
>
>
> --
> View this message in context: http://ilwis.forum.52north.org/Water-detection-tp4025787.html
> Sent from the 52° North - ILWIS Community Forum mailing list archive at Nabble.com.
> _______________________________________________
> Ilwis mailing list
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> Please respect our mailing list guidelines:
> http://52north.org/resources/mailing-lists-and-forums/guidelines

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Re: Water detection

sander.z
Hello, i tried your option but there is a problem. When i load the .tif image it creates 4 images (band 1-4 i think), but the 4th one is all white (255).
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Re: Water detection

Bas Retsios
Hi!

Check the data-provider what the 4 bands are. Quite likely you are
dealing with an RGB photo, not an actual satellite image.
The 4th band is then probably the intensity ("alpha") channel, so it is
okay to have all values set to 255 ("opaque", thus not "transparent" or
"semi-transparent").

Bas Retsios
ILWIS team



On 17/3/2015 16:30, sander.z wrote:

> Hello, i tried your option but there is a problem. When i load the .tif image
> it creates 4 images (band 1-4 i think), but the 4th one is all white (255).
>
>
>
> --
> View this message in context: http://ilwis.forum.52north.org/Water-detection-tp4025787p4025791.html
> Sent from the 52° North - ILWIS Community Forum mailing list archive at Nabble.com.
> _______________________________________________
> Ilwis mailing list
> [hidden email]
> http://list.52north.org/mailman/listinfo/ilwis
> http://ilwis.forum.52north.org
> Please respect our mailing list guidelines:
> http://52north.org/resources/mailing-lists-and-forums/guidelines

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Re: Water detection

kumarbj
Ilwis team

Is Ilwis compatible with windows 8.1 ?
I am not able open sat. Data n the same Ilwis version which worked smoothly in Windows 8.
Can you help?

Jaya Kumar

Sent from my iPad

> On 18-Mar-2015, at 14:51, Bas Retsios <[hidden email]> wrote:
>
> Hi!
>
> Check the data-provider what the 4 bands are. Quite likely you are dealing with an RGB photo, not an actual satellite image.
> The 4th band is then probably the intensity ("alpha") channel, so it is okay to have all values set to 255 ("opaque", thus not "transparent" or "semi-transparent").
>
> Bas Retsios
> ILWIS team
>
>
>
>> On 17/3/2015 16:30, sander.z wrote:
>> Hello, i tried your option but there is a problem. When i load the .tif image
>> it creates 4 images (band 1-4 i think), but the 4th one is all white (255).
>>
>>
>>
>> --
>> View this message in context: http://ilwis.forum.52north.org/Water-detection-tp4025787p4025791.html
>> Sent from the 52° North - ILWIS Community Forum mailing list archive at Nabble.com.
>> _______________________________________________
>> Ilwis mailing list
>> [hidden email]
>> http://list.52north.org/mailman/listinfo/ilwis
>> http://ilwis.forum.52north.org
>> Please respect our mailing list guidelines:
>> http://52north.org/resources/mailing-lists-and-forums/guidelines
>
> _______________________________________________
> Ilwis mailing list
> [hidden email]
> http://list.52north.org/mailman/listinfo/ilwis
> http://ilwis.forum.52north.org
> Please respect our mailing list guidelines:
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Re: Water detection

schouwenburg
Hi,
Ilwis is not tested on windows 8 or later for the moment. Our development environment is windows 7. From a personal observation I can say that I didn’t find any problems on windows 8.1 which runs on my own laptop. Granted, I didn’t test extensively there, but it seemed to work normally.

Martin Schouwenburg
[hidden email]

-----Original Message-----
From: Ilwis [mailto:[hidden email]] On Behalf Of B Jaya Kumar
Sent: maandag 23 maart 2015 7:02
To: Retsios, V. (ITC)
Cc: sander.z; [hidden email]
Subject: Re: [Ilwis] Water detection

Ilwis team

Is Ilwis compatible with windows 8.1 ?
I am not able open sat. Data n the same Ilwis version which worked smoothly in Windows 8.
Can you help?

Jaya Kumar

Sent from my iPad

> On 18-Mar-2015, at 14:51, Bas Retsios <[hidden email]> wrote:
>
> Hi!
>
> Check the data-provider what the 4 bands are. Quite likely you are dealing with an RGB photo, not an actual satellite image.
> The 4th band is then probably the intensity ("alpha") channel, so it is okay to have all values set to 255 ("opaque", thus not "transparent" or "semi-transparent").
>
> Bas Retsios
> ILWIS team
>
>
>
>> On 17/3/2015 16:30, sander.z wrote:
>> Hello, i tried your option but there is a problem. When i load the
>> .tif image it creates 4 images (band 1-4 i think), but the 4th one is all white (255).
>>
>>
>>
>> --
>> View this message in context:
>> http://ilwis.forum.52north.org/Water-detection-tp4025787p4025791.html
>> Sent from the 52° North - ILWIS Community Forum mailing list archive at Nabble.com.
>> _______________________________________________
>> Ilwis mailing list
>> [hidden email]
>> http://list.52north.org/mailman/listinfo/ilwis
>> http://ilwis.forum.52north.org
>> Please respect our mailing list guidelines:
>> http://52north.org/resources/mailing-lists-and-forums/guidelines
>
> _______________________________________________
> Ilwis mailing list
> [hidden email]
> http://list.52north.org/mailman/listinfo/ilwis
> http://ilwis.forum.52north.org
> Please respect our mailing list guidelines:
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