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Posts: 4
Registered: ‎01-18-2019
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Procedure for changing the pixel values inside an AOI using ERDAS 18

The procedure for changing the pixel values inside an AOI (that worked for previous version) doesn't seem to work for ERDAS 18. It seems like it works, until you save the modified image. At that moment, the modified pixels go back to their original values. Does anyone know how to solve this?

 

This is the procedure that used to work...

Using the Area Fill tool is an easy way to change the values of a raster image using an AOI as a mask in the IMAGINE 2D View. Open your image in an IMAGINE 2D View. Place an AOI point on the pixel that you wish to change. Make sure that the AOI is selected. Open the Area Fill tool by clicking on the Fill icon in found in the Edit group under the Multispectral tab. You must highlight the name of your raster image in the Contents panel for the Multispectral tab to be displayed. In the Area Fill tool make sure that the Function option is set to Constant and that the Fill With value is set to the new pixel value(s) that you want. Click the Apply button to convert the pixel value under the AOI point to the new pixel value. A warning message will pop up saying "Since this function modifies the pixel values of the image, you may wish to recalculate the statistics and histogram for the layer before doing any other operation that depends on this data.” Click OK. Save your image. An Attention message pops up saying “Some edits could permanently change pixel values in the image. Do you want to continue?” Click Yes.

 

 

I appreciate any help on this matter.

 

Mariana

Technical Evangelist
Posts: 665
Registered: ‎10-01-2015

Re: Procedure for changing the pixel values inside an AOI using ERDAS 18

[ Edited ]

Hi Mariana,

 

That exact workflow just worked for me. But I'm using ERDAS IMAGINE 2018 Update 2. Do you have Update 2 installed?

 

Also - what format is the data? How many bands? What bit-depth? Is it thematic or athematic?

 

In which version of ERDAS IMAGINE did this workflow work with this data?

 

Cheers

 

Ian Anderson
Chief Product Owner, Desktop Remote Sensing
Hexagon Geospatial
MP
New Contributor
Posts: 4
Registered: ‎01-18-2019

Re: Procedure for changing the pixel values inside an AOI using ERDAS 18

Ian,

 

The mentioned procedure works with ERDAS 14 and 16 for sure. I'm not sure if I have installed the Update 2. Would the workflow work without the update?

 

I'm working with an Evapotranpiration image (IMAGINE image, 1 band, 32 bit) obtained using a Landsat 5 image. I used to follow this workflow to assign a value to clouded areas (for which I created polygons within the AOI). Once I had my masked image, I used a model that replaces all the areas with the value I assigned to the AOI polygons for another image without clouds, while keeps the rest of the original image.

 

Thanks,

 

Mariana

Technical Evangelist
Posts: 665
Registered: ‎10-01-2015

Re: Procedure for changing the pixel values inside an AOI using ERDAS 18

Hi Mariana,

 

I don't know if there were any Raster Edit changes in Update 1 or 2, but I'd highly recommend moving to Update 2 anyway.

 

I tried editing again this morning specifically with a 32-bit single band image and didn't have any problems performing and saving a raster edit function. One thing you do have to watch out for is that any existing pyramid layers are not edited, so you'll need to re-build pyramids after performing the edit if you have them.

 

Cheers

 

Ian Anderson
Chief Product Owner, Desktop Remote Sensing
Hexagon Geospatial
MP
New Contributor
Posts: 4
Registered: ‎01-18-2019

Re: Procedure for changing the pixel values inside an AOI using ERDAS 18

Good morning Ian,

 

Thanks for your reply. I tried again, and it worked, although I had to keep the original raster name. If I use the "save as", and change the name of the file, the edited values are no longer there. There was no such problem with the previous ERDAS versions. I need to check if the problem was the lenght of the file name or use of special characters (like an undescore, "_") within the name. 

 

Thank you very much for your help with this matter. I really appreciate it.

 

Mariana

Technical Evangelist
Posts: 665
Registered: ‎10-01-2015

Re: Procedure for changing the pixel values inside an AOI using ERDAS 18

Hi Mariana,

 

I tried a quick Save As.., (from the Contents panel) and that worked fine too, so perhaps it's something specific in the workflow you are taking. 

You may want to log a Support Ticket to get assistance in troubleshooting the issue. 

 

Another alternative would be to use a Spatial Model to change the pixel values within the AOI extents to a specific DN value.

 

Cheers.

 

Ian Anderson
Chief Product Owner, Desktop Remote Sensing
Hexagon Geospatial
MP
New Contributor
Posts: 4
Registered: ‎01-18-2019

Re: Procedure for changing the pixel values inside an AOI using ERDAS 18

Ian,

 

Thanks for your suggestions. I'll try those.

 

Mariana

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