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Topic: trouble of orthorectification about spot images sample

first question:
- Can I orthorectified the reference spot image (1998) with the envi option Tools/preprocessinge/spot... with the use of the dem that was available in the sample?

second question:
-when i'm going to do the orthorectification/resampling of the second image I don't know which tool use in MAP GRID. Can you help me about?

third question:
- I've got trouble of correlation (...origin and resolution).

I'll hope in your answers!

Dan (sorry for my bad english)

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Re: trouble of orthorectification about spot images sample

Hi Dan,

You questions in order:

1- No, you cannot use the ENVI tool to orthorectify the SPOT image, the quality will not be good enough and for this particular image, you also need to generate GCP

2- "From raw image": you define an output grid that corresponds to the image you're inouting, the most common option. "From georeferenced Image": the grid will be identical to the footprint of another image you can provide as input. "Manual Edit": if you want to specify all parameters manually

3- You need to make sure the images are defined on a common grid so you can safely correlate the images. To this end, don't forget to click on the button "Adjust grid to multiple of resolution" when you define your grid.

Hope this help,
Sebastien

3 (edited by Delghe 2010-01-29 04:46:59)

Re: trouble of orthorectification about spot images sample

when the process of Orthorectification is finished program gives me a TRAPPED ERROR but at the same time gives me the Mappinmatrices.mat.
I do not understand that.

4 (edited by Delghe 2010-01-29 06:23:32)

Re: trouble of orthorectification about spot images sample

3- You need to make sure the images are defined on a common grid so you can safely correlate the images. To this end, don't forget to click on the button "Adjust grid to multiple of resolution" when you define your grid.  ----> I did this but i've got the same problem. I'm crying.

So my problem are:
1) i create the shade image like Sebastian said me but then i'm not ableto select tie points between this shade image and the first spot image to orthorectify

2) in thi first process when i do te orthorecthification i have to select "from raw image and click over adjust.....etc"?

3) at the end of orthorectification process Cosi-corr give me a trouble of resampling. Why?

4) then i do the resampling and programm will  give me the first image

5) then i have to do the same process with the new ortho image and the secondo spot image

6) when i do the orthorectification of the second image i selected FROM RAW IMAGE and click over ADJUST....

7) but also, there is the problem of Origin and resolution when i do the correlation

i don't known why. I'm very sad. If you Sebastian can give me the step of the complite process with more details i'll will send you thousend thanks because i'm stopped and i can't work. I don't know more what to do. I tried everything but i never do a correct correlation. It's very difficoult.

I hope that someone can help me.

Dan

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Re: trouble of orthorectification about spot images sample

Hi Dan,

If you click on "adjust grid ot multiple of resolution," for EACH image, you should not have pb correlating the images

1- Selecting tie point between a shaded DEM and an image is not always easy, it requires you to recognize the topographic structures on your image. The image you're using is supposed to be an "easy" one. It's better if you use a large screen to have a global view. You will see that, or course, the DEM and the raw image don't line up, that's what makes it hard.

2- yes

3- what kind of resampling trouble are you facing? Have you check the image tile size and image cache size in ENVI?

4- ok

5- yes

6- yes

7- that's not supposed to happen, mostly with the sample images that have been well tested. Please post the .hdr files of the 2 spot ortho images on the forum

You seem to be doing things better than yesterday, maybe you forgot to mention something that makes to whole thing not working. Make sure you don't have any error message and that cache and tile sizes are well configured, then restart ENVI and redo the processing.

Good luck,
Sebastien

6 (edited by Delghe 2010-01-29 10:16:21)

Re: trouble of orthorectification about spot images sample

I wrote all my steps i've done on a private message.

PS For the point 1)... when i selected tie points between the shaded image and the first spot image it's like that there are to compare two different images. so when i chase the tie points it's like a random process. If the selection was not corret it's a big problem or the post analysis at minimum square can resolve the trouble?

PPS Now i can't use Envi 'cause i've not the license of the program. Tomorrow I can do it newly and i will send you the hdr file

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Re: trouble of orthorectification about spot images sample

Selecting tie points is clearly not a random process and it's very well defined. It's not always easy to do but large structures are always easy to recognize.

Sebastien

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Re: trouble of orthorectification about spot images sample

I know that it was not a random process but i thougth that the minimal square process could give a sort of precision of this.

I don't recognize large structures in the Shade image. I only see an image in grey scale that seems completely different from the pre event spot image!

Thanks

Dan

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Re: trouble of orthorectification about spot images sample

Now i, finally, finally individuate tie points between shade image and first spot image thanks to a particoular rock structure that i recognize in both images and give me the start to search other tie points.

Now i will to orthorectified first spot image (after click ADJUST in map grid). I hope, this time, i will not have trouble of overlapping.
I'm sorry, Sebastien, for the private mail i sent you.

Now i will go next with the analysis. I hope it will go succefully. If I will have the same problem of overlapping i'll sent you the Hdr file to understand where I've done mistakes.

Thousend thanks

I hope all these trouble i'm having and posting in this forum can be to help from other users of this forum which use, for the first time, cosi-corr

Dan