Christian Kohler
New Member
Posts:1  
| 14 Dec 2022 07:15 AM |
|
|
Hi!
Currently I am investigating differences in some data, in case two DEM files. Therefore I used the Change Detection Difference Map dialog in ENVI which is working perfectly fine and fast, but as I want to use it several time I am looking a possibility to recreate this functionality in IDL.
Trying to recreate the functionality in IDL I used the following functions (firstly using ENVI modeler and then exported to IDL):
1. Generate Tie Points by Mutual Information
2. Filter Tie Points by Global Transform (also tried Fundamental Matrix and Pushbroom Model here)
3. Image To Image Registration
4. Subtract results and display
But the calculation time is way longer than using the dialog and I get a non-zero difference between the two DEM files which does not appear using the ENVI dialog. Anyone can indicate the correct IDL equivalence and clarify why, running the IDL function, I get a non-zero difference I do not see using ENVI dialog.
Cheers
Christian
|
|
|
|
Ben Castellani
Basic Member
Posts:130 
| 15 Dec 2022 12:43 PM |
|
|
Does your workflow go quickly when running your model in ENVI Modeler? Is it only slow after exporting to IDL and running directly there? It may help if you post here your full IDL code so we have a chance to see why it is running slow and why there is no change detected.
|
|
|
|
Christian Kohler
New Member
Posts:1
| 16 Dec 2022 10:12 AM |
|
|
I don't think there is a lot difference changing the order.
As far as I think I found out, the dialog box simply uses something like the "ImageIntersection" function, which produces compatible results in terms of speed and difference. Maybe someone with more experience on using the dialog / the function can comment on this.
Besides if I run my DEM files through CoRegistration before doing the ImageIntersection I get differences between two DEM which are not present when directly inserting them into ImageIntersection. How is ImageIntersection supposed to be used, should I do CoRegistration first, always? or in which cases?
|
|
|
|
MariM
Veteran Member
Posts:2396 
| 20 Dec 2022 08:32 AM |
|
|
Can you post the code you generated from the modeler and are using for comparison?
I assume you are trying to recreate this workflow?
https://www.l3harrisgeospatial.com/docs/ImageChange.html
There are many different settings you can use in this workflow and you can choose to co-register your images if needed (if they are significantly offset from each other in spatial positioning). We would need to confirm you are using the same bands and parameters in the workflow and in your code.
|
|
|
|