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Contributor
Posts: 26
Registered: ‎05-22-2017
Accepted Solution

Transforming several ESRI ASCII Grid Files to one GeoTIFF

Dear all

 

We would like to transform several ESRI ASCII Grid Files to one GEOTIFF File with the Terrain Prep Tool. But if we try to import one of our Grid Files in the following way: --> Edit --> Add DTM --> File Type (*.asc), Erdas doesn’t response anymore. It is a DTM.

 

It seems like our ASCII file (see attachment) doesn’t fulfill the following requirement:

ASCII DTM is a Socet Set DTM format (*.asc) and is only supported in the 4-column format - supports point data and breaklines. Four-column data include X,/Y/Z information, and Point Code (mass point, breakline start or breakline continue).

 

Our ASCII File has up to 6000 columns. Hence, it seems like we have to pre-process our files. If yes, is there a tool in Erdas Imagine and could you also explain how we have to manage this?


Perhaps somebody knows another method to import our .asc Files and export it as one GeoTIFF File in Erdas-Imagine (or with an open-source product)

 

I would be very grateful if someone could help me in this matter.

 

Regards
Sajan

Contributor
Posts: 26
Registered: ‎06-01-2016

Re: Transforming several ESRI ASCII Grid Files to one GeoTIFF

Hello Sajan, 

 

Unfortunately, Imagine does not support ESRI ASCII format. The files need to be converted into an IMAGINE acceptable format like .img or tiff. This discussion may help you :http://community.hexagongeospatial.com/t5/Support-ERDAS-IMAGINE/ASC-DEM-FILES/m-p/14258/highlight/tr...

 

Once it is in .img format you can just mosaic the tiles in Mosiac pro. 

Contributor
Posts: 26
Registered: ‎05-22-2017

Re: Transforming several ESRI ASCII Grid Files to one GeoTIFF

[ Edited ]

Hi Emily

 

Thank you for your help! Smiley Happy

I converted the files into .img and i tried to mosaic these filese in Mosaic pro.

Unfortunately, you see the boundaries of the individual tiles (after merging them into one big .img file).

 

Are there any further settings needed to manage this issue? I think i have to define the individual pixel values (max,min) for each tile somewhere. But do you know, where i can do that (perhaps with a AOI file)?

 

Erdas_imagine.JPG

 

Thanks a lot!

Sajan

 

Staff
Posts: 203
Registered: ‎02-12-2016

Re: Transforming several ESRI ASCII Grid Files to one GeoTIFF

Hello Sajan,

 

You should not notice seams along the tile edges unless the image values along the seams are different. If this is a screenshot of the image after MosaicPro, the image value differences existed before adding them to MosaicPro or some option in MosaicPro was used to remap the values differently.

 

If the screenshot was captured in the MosaicPro canvas, don’t worry about it. Images could be displayed differently in MosaicPro because of differences in the statistical content of the individual tiles.

 

Regards,

Jeff

Contributor
Posts: 26
Registered: ‎05-22-2017

Re: Transforming several ESRI ASCII Grid Files to one GeoTIFF

HI Jeff

 

Thanks for your reply! It's a screenshot from Erdas Imagine (after merging the several .img Files into 1.img file)

Yes, it seems like that one has to define the max & min gray values before processing them in ER MAPPER. But I couldn't find any relevant setting to do that. A customer did it via FME and the gray values were automatically adapted (but FME increases the file size by huge amounts, which is rather bad for further processing steps).

 

But it looks like a display error. The relevant "height" values are correct and thus, it's suitable to use it for further processing.
Perhaps it's possible to pass a filter after Mosaic Pro (if somebody needs a correct representation of the DTM). But in my case, that was not necessary anymore.

 

Thanks to all!

Sajan

 

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