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trouble with georeferenced images

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Message 1 of 8
autoMick
842 Views, 7 Replies

trouble with georeferenced images

I'm struggling with this...

I have numerous images captured through side-scan sonar which are apparently georeferenced. I was trying to mapiinsert them, after setting a coordinate system, but can't seem to find the right coordinate system to put them in the right spot (i.e. at real world coordinates). The world file with should be WGS84 lat longs with coodinates as decimal degrees.

Could someone have a look and suggest a workflow?

I've attached all the files relating to one of the images.

Thanks

- Mick

 

Civil3d user in Australia since 2012.
7 REPLIES 7
Message 2 of 8
antoniovinci
in reply to: autoMick

First of all, please tell us: are we talking about a point on the south of Brisbane?

If so, try to _MAPIINSERT the attachment, and let us know what's goin' on, sir.

Message 3 of 8
autoMick
in reply to: antoniovinci

That attachment works perfectly Antonio. The location is south of Brisbane as you have plotted.

How did you achieve that?

Also, is there a setting that will remove the black infill around the skewed image. I actually have about 50 of these images that are a continuous series that should display seamlessly together.

Thanks

- Mick

Civil3d user in Australia since 2012.
Message 4 of 8
antoniovinci
in reply to: autoMick

The transformation of a "stupid" pair PNG/PGW into a "clever" GeoTIFF involves the following steps:

  1. convert PNG => TIF (e.g. thru Irfanview)
  2. rename PGW => TFW
  3. injection of the EPSG header within the TIF file of point #1 (e.g. thru Qgis)

About the 50 unnecessary frames, I don't know any automatic ways to get rid of 'em, so I fear you should run (50 times) the _IMAGECLIP command in Autocad, sir.

Message 5 of 8
autoMick
in reply to: antoniovinci

Thanks Antonio,

OK so quite a process then, I thought I was just missing something with mapcsassign or similar.

  1. Infraview is a neat little program - nice batch conversion feature. I'd never heard of this program before.
  2. Batch rename of PGW was quick in DOS
  3. Next stage using QGIS I had no idea on... I downloaded the program and did a bit of exploring, but now it's late.. so will have to wait till tomorrow. Any help on this stage would be appreciated. Can it be done in a batch process?

I looked at imageclip, but it looks like it only does rectangular clip? Slow process as well.

Maybe there is a way to make the black frame transparent in the image?

 

thanks

- Mick

 

Civil3d user in Australia since 2012.
Message 6 of 8
antoniovinci
in reply to: autoMick


autoMick wrote:

Maybe there is a way to make the black frame transparent in the image? 


Good point, sir: load the attachment as usual, then set TRANSPARENCY=YES in its properties.

If it works, the only difference among skennars_head.tif is the alpha channel on the 0 value of band #4.

 

P.S.

If you wanna get info about the powerful opensource Qgis, surf the Tube which contains a lot of tutorials about.

Message 7 of 8
autoMick
in reply to: antoniovinci

Thanks Antonio, I've got a bit of learning to do!

- Mick

Civil3d user in Australia since 2012.
Message 8 of 8
antoniovinci
in reply to: autoMick

You're welcome, dear Aussie: by the way, set _IMAGEFRAME = 0 in order to hide the raster boundary.

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