Raster Layers Projection

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plavadinho
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Joined: Wed May 06, 2009 8:21 pm

Raster Layers Projection

Postby plavadinho » Fri May 15, 2009 2:42 am

Hello!

I need some help here please.

Can someone tell me if Digiterra alows the use of raster images with a prj file to georeferenciate the raster layers like the ArcPAD does? The workflow is the same?

Thanks!

Pedro Fernandes

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Balazs Hober
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Re: Raster Layers Projection

Postby Balazs Hober » Fri May 15, 2009 8:43 am

Hi Pedro,

Have you read the following topic already: viewtopic.php?f=10&t=59? Actually raster images can be georeferenced with the Raster orientation tool.

We have two option to do this:
1. Georeferencing on the screen by manually
2. Georeferencing by coordinates

Our software use the WORLD file format for georeferencing as you can see on the [urlhttp://www.digiterra.hu/distribution/viewtopic.php?f=10&t=59]mentioned topic[/url]. JGW to JPEG, TFW to TIFF etc.

Used as attribute file associated with corresponding image file.
World files consist of 6 lines, denoting the following:

Code: Select all

sampleRasterFile.tfw
3.000000000000   (size of pixel in x direction)
0.000000000000   (rotation term for row)
0.000000000000   (rotation term for column)
-3.000000000000   (size of pixel in y direction)
934169.690845528910   (x coordinate of center of upper left pixel in map units)
236523.318065105000   (y coordinate of center of upper left pixel in map units)

Using the world file, image files can be used in most desktop GIS software and coordinates can be inputted from the world file to maintain geographic integrity.

Any question?

plavadinho
Posts: 15
Joined: Wed May 06, 2009 8:21 pm

Re: Raster Layers Projection

Postby plavadinho » Fri May 15, 2009 11:02 am

Hello again!

Thank you for the explanation.

I am asking this because almost all raster files that we have come with a prj or tfw file (the majority with a prj file).

It is simpler if i use the prj file with the jpg image (all together in the same folder) - Can i work this way?

The prj file has the following structure:

PROJCS["Lisboa_Hayford_Gauss_IGeoE",GEOGCS["GCS_Datum_Lisboa_Hayford",DATUM["D_Datum_Lisboa_Hayford",SPHEROID["International_1924",6378388,297]],PRIMEM["Greenwich",0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",200000],PARAMETER["False_Northing",300000],PARAMETER["Central_Meridian",-8.13190611111111],PARAMETER["Scale_Factor",1],PARAMETER["Latitude_Of_Origin",39.6666666666667],UNIT["Meter",1]]

If i can use directly the already existing prj or tfw files it would be easier than create a new georeferetiation file.

Thanks in advance.

Pedro Fernandes

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Balazs Hober
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Re: Raster Layers Projection

Postby Balazs Hober » Fri May 15, 2009 11:59 am

Hi Pedro,
You need to use only the WORLD file for the raster image in DigiTerra Explorer. Please play attention to that you have to use x,y coordinates in the current projection in your WORLD file. And of course you need to select the appropriate projection for GPS data collection.

Let me know if you have any other issues or have any other questions as I'd be glad to help! ;)


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