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Coordinate transformation of image file

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Message 1 of 37
nomisc
2044 Views, 36 Replies

Coordinate transformation of image file

I have a satellite image file originally created with WGS 1984. I need to use it in a drawing with British National grid co-ordinates. In Arc I redefined the projection to British grid, but when I import it still comes in using the WGS co-ordinates and is consequently in completely the wrong place. I've looked at various threads, but all seem to deal with drawing or vector data rather than raster. Any help most appreciated.

36 REPLIES 36
Message 21 of 37
nomisc
in reply to: antoniovinci

Hi Antonio,

 

As you'll see from the attached this comes in to roughly the same area, though not exactly. What is your "insane" idea?

 

 

Georeferencing_error4.jpg

 

Cheers

 

Simon

 

Message 22 of 37
nomisc
in reply to: Pointdump

Hi Dave,

 

I am indeed using metric, which is why I was surprised to find my default insertion units were inches, but heigh ho. We are definitely making progress though.

 

Cheers

 

simon

Message 23 of 37
antoniovinci
in reply to: nomisc


nomisc wrote:
What is your "insane" idea?

Well, since your original TIFF is too huge to be handled, I guess you can shrink it somehow:

1] please copy and paste the following worldfile code in Notepad (taken from your metadata), and save it as SHOTLEY.TFW

            0.3164
            0.0000
            0.0000
           -0.3164
       619509.7410
       238511.9190

2] open up your monster TIFF in a graphic editor (e.g. Irfanview), then decrease its colour depth to 256, finally save it as SHOTLEY.TIF with LZW compression

3] ensure that SHOTLEY.TFW and SHOTLEY.TIF lay in the same folder

4] try now to load the latter in Autocad Map: what happens?

Message 24 of 37
Pointdump
in reply to: antoniovinci

Antonio,

 

"A geo-referenced image needs neither any Worldfile (because it already contains the geo-header) nor any .PRJ (concerning vector shapes only)..."

 

So, in this case, Shotley.tfw would overrule the geo-header in Simon's tiff?

 

How did you learn how to deal with all of these geo-files?

 

Dave

Dave Stoll
Las Vegas, Nevada

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Message 25 of 37
Alfred.NESWADBA
in reply to: Pointdump

Hi,

 

>> So, in this case, Shotley.tfw would overrule the geo-header in Simon's tiff?

In dialog _MAPIINSERT you can select the correlation source, so it's up to the user which georef-info should be used.

 

2014-11-12 11-06-05.png

 

- alfred -

------------------------------------------------------------------------------------
Alfred NESWADBA
Ingenieur Studio HOLLAUS ... www.hollaus.at ... blog.hollaus.at ... CDay 2024
------------------------------------------------------------------------------------
(not an Autodesk consultant)
Message 26 of 37
antoniovinci
in reply to: Pointdump

Pointdump wrote:

So, in this case, Shotley.tfw would overrule the geo-header in Simon's tiff?


No, Dave, just because when you modify an image in a graphic editor like Irfanview, you're losing every geo-header: in this case, a worldfile is MANDATORY.


The goal of my test is the following: if the 256-color ortho will load, it will be proved the issue is caused by the colour depth.


Whereupon, we'll be able to reconstruct the suitable geo-header: stay tuned, sir.

Message 27 of 37
nomisc
in reply to: antoniovinci

Hi Antonio,

 

Again, close, but no cigar. This puts the image in the same location as I managed with Dave after changing my input units from inches to metres, but it's still not quite right.

 

I've had a thought and cut out a small segment of the original image as I figure if we can get that to work we can do the whole thing. It's attached so do your magic.

 

Thanks

 

Simon

Message 28 of 37
Pointdump
in reply to: Alfred.NESWADBA

Alfred,

 

As usual, you cut to the heart of the matter. Thank you. Is there also a place to change the "Image Correlation" in the FDO Connection?


Data.png


How do you decide whether to use Data Connect or MAPIINSERT?

 

Dave

Dave Stoll
Las Vegas, Nevada

EESignature

64GB DDR4 2400MHz ECC SoDIMM / 1TB SSD
NVIDIA Quadro P5000 16GB
Windows 10 Pro 64 / Civil 3D 2024
Message 29 of 37
Pointdump
in reply to: antoniovinci

Antonio,

 

"...when you modify an image in a graphic editor like Irfanview, you're losing every geo-header..."

 

So that would be the subtle distinction in whether a file is called a TIFF or a GEO-TIFF.

 

"...stay tuned, sir."

 

I'm glued to this Forum. Thank you, Master Antonio!

 

Dave

Dave Stoll
Las Vegas, Nevada

EESignature

64GB DDR4 2400MHz ECC SoDIMM / 1TB SSD
NVIDIA Quadro P5000 16GB
Windows 10 Pro 64 / Civil 3D 2024
Message 30 of 37
Alfred.NESWADBA
in reply to: Pointdump

Hi,

 

>> Is there also a place to change the "Image Correlation" in the FDO Connection?

No, at least I don't know an option to switch that.

In case of difficulties I would create a world-file and remove the georef-info from the image header.

 

>> How do you decide whether to use Data Connect or MAPIINSERT?

MAPIINSERT created referenced images that are (in most cases) faster on display. So PAN & ZOOM is faster.

...while MAPCONNECT/FDO can use coordinate systems 😉

 

- alfred -

------------------------------------------------------------------------------------
Alfred NESWADBA
Ingenieur Studio HOLLAUS ... www.hollaus.at ... blog.hollaus.at ... CDay 2024
------------------------------------------------------------------------------------
(not an Autodesk consultant)
Message 31 of 37
Pointdump
in reply to: Alfred.NESWADBA

Alfred,

 

"In case of difficulties I would create a world-file and remove the georef-info from the image header."

 

OK, so any image-editing will remove the geo-header, right? How do you correlate the image if the geo-reference is gone? How does a World File reference an image?

 

Dave

Dave Stoll
Las Vegas, Nevada

EESignature

64GB DDR4 2400MHz ECC SoDIMM / 1TB SSD
NVIDIA Quadro P5000 16GB
Windows 10 Pro 64 / Civil 3D 2024
Message 32 of 37
Alfred.NESWADBA
in reply to: Pointdump

Hi,

 

>> so any image-editing will remove the geo-header, right?

Any image editing done with tools not knowing anything about a georef-info in the file-header, that is correct.

But there are also tools out in www that can handle image headers to define their georeference position/rotation/scaling.

 

>> How do you correlate the image if the geo-reference is gone?

First at all, I would like to save the georef-info and try not to lose them, so e.g. inserting the image in AutoCAD and then let RasterDesign create a world-file 😉

If I don't have any georef-info I would use e.g. RasterDesign (up to rubbersheeting) or AutoCAD command _ALIGN or Map 3D commands _ADETRANSFORM or _ADERSHEET.

 

>> How does a World File reference an image?

Described >>>there<<<.

 

- alfred -

------------------------------------------------------------------------------------
Alfred NESWADBA
Ingenieur Studio HOLLAUS ... www.hollaus.at ... blog.hollaus.at ... CDay 2024
------------------------------------------------------------------------------------
(not an Autodesk consultant)
Message 33 of 37
Pointdump
in reply to: Alfred.NESWADBA

Thank you, Alfred. I've used _ALIGN many times, but I didn't know about _ADETRANSFORM or _ADERSHEET. I also didn't know about RasterDesign. I just did some reading about it in the Help Files. I'll investigate further.

 

Dave

Dave Stoll
Las Vegas, Nevada

EESignature

64GB DDR4 2400MHz ECC SoDIMM / 1TB SSD
NVIDIA Quadro P5000 16GB
Windows 10 Pro 64 / Civil 3D 2024
Message 34 of 37
antoniovinci
in reply to: nomisc


nomisc wrote:
cut out a small segment of the original image

Check the attachment out: any changes?


Please tell me: were you able to load the full color 1.5 GB imagery, or only my decreased 256-color release..?

Message 35 of 37
nomisc
in reply to: antoniovinci

Hi Antonio,

 

That works Smiley Very Happy What's more it's part of the original 1.5MB file, not the 256 version. Please tell me what you did.

 

With reference to the whole image, I was able to load the entire file, but as discussed it was in the wrong place. However, if the segment could be loaded the same rules should work for the whole image. My only slight worry is that the image has a frame around it with no data, but hopefully that shouldn't affect it.

 

Thanks again for all your help.

 

Simon

Message 36 of 37
antoniovinci
in reply to: nomisc

Simon, I'm as glad as confused, because the metadata you pasted referred to metric units, while Segment.TFW contains lat/long coordinates...

Regardless of the huge 1.5 GB file stores degrees or meters, you should convert it to the following CRS:

EPSG:27700

If you don't know how to do it, ask your Gis crew, since it's not so easy as appears.

 

Message 37 of 37
nomisc
in reply to: antoniovinci

Hi Antonio and Dave,

 

Success!! Smiley Very Happy It transpires we were very nearly there before when I converted from inches to metres. It turns out that there are a number of different transformations from WGS 1984 to OSGB (aka 27700) and the particular satellite imagery I have works best with OSGB_1936_To_WGS_1984_3 rather than the default OSGB_1936_To_WGS_1984_1! Smiley Frustrated and that is what makes the subtle difference. You gave me the idea, Dave, when you mentioned the difference between US Survey Feet and International Feet so I spoke to one of our GIS guys and hey presto.

 

Thanks everyone for all your help and suggestions

 

Simon

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