[Geotiff] Re: Geotiff Digest, Vol 26, Issue 1

[Prajjval]

Hello,

I think that there is no such difference in reading the geotiff, either it
is a DEM or anything else.
So read the geotiff image data and use it as is. Means it does not matter
that the data is DEM or pixel value. The DEM data which is in geotiff format
means that the values stored in it are height.

Also the value stored in geotiff is always used as it is and it is not
relative to anyother value.

The ModelTiepointTag stores the top left location of your geotiff image. And
ModelPixelScaleTag stores the pixel size of your geotiff image.

Vineet Bhargava
India

Firstly I am  new to the geotiff world .


I am trying to  read DEM data which is supplied in geotiff format. Its
geotiff image with 181 rows x 181 cols
I  wrote some code to read the basic tags. And they are as follows

SAMPLESPERPIXEL  1
TIFFTAG_BITSPERSAMPLE  16
TIFFTAG_PHOTOMETRIC  1     (1       /* min value is black */ )
TIFFTAG_PLANARCONFIG  1   ( single plane image)

Now my doubt how do I read the height data stored in this Geotiff Image
?
And is this height stored relative to some value ( like any value seen
in  ModelTiepointTag  .. )

Any API's in libgeotiff  / pointers on handling Digital Elevation data
in geotiff will be appreciated .



FYI ..
This is the Geotiff info for the input data

Geotiff_Information:
   Version: 1
   Key_Revision: 1.0
   Tagged_Information:
      ModelTiepointTag (2,3):
         0                0                0
         6.99861111       54.0013889       0
      ModelPixelScaleTag (1,3):
         0.00277778       0.00277778       0
      End_Of_Tags.
   Keyed_Information:
      GTModelTypeGeoKey (Short,1): ModelTypeGeographic
      GTRasterTypeGeoKey (Short,1): RasterPixelIsArea
      GeographicTypeGeoKey (Short,1): GCS_WGS_84
      GeogCitationGeoKey (Ascii,6): "wgs84"
      GeogAngularUnitsGeoKey (Short,1): Angular_Degree
      End_Of_Keys.
   End_Of_Geotiff.


Thanks in advance,
--Chandrakant

On 9/6/06, geotiff-request at lists.maptools.org <
geotiff-request at lists.maptools.org> wrote:
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> Today's Topics:
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>    1. Processing Elevation data in Geotiff
>       (Chandrakant Mohire (RBIN/ECM2))
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Wed, 6 Sep 2006 14:58:07 +0530
> From: "Chandrakant Mohire (RBIN/ECM2)" <Chandrakant.M at in.bosch.com>
> Subject: [Geotiff] Processing Elevation data in Geotiff
> To: <geotiff at lists.maptools.org>
> Message-ID:
>         <6222DD7606D1314C85F63D9CF40207E00304C87C at kormail02.in.bosch.com>
> Content-Type: text/plain; charset="us-ascii"
>
> Hello ,
>
> Firstly I am  new to the geotiff world .
>
>
> I am trying to  read DEM data which is supplied in geotiff format. Its
> geotiff image with 181 rows x 181 cols
> I  wrote some code to read the basic tags. And they are as follows
>
> SAMPLESPERPIXEL  1
> TIFFTAG_BITSPERSAMPLE  16
> TIFFTAG_PHOTOMETRIC  1     (1       /* min value is black */ )
> TIFFTAG_PLANARCONFIG  1   ( single plane image)
>
> Now my doubt how do I read the height data stored in this Geotiff Image
> ?
> And is this height stored relative to some value ( like any value seen
> in  ModelTiepointTag  .. )
>
> Any API's in libgeotiff  / pointers on handling Digital Elevation data
> in geotiff will be appreciated .
>
>
>
> FYI ..
> This is the Geotiff info for the input data
>
> Geotiff_Information:
>    Version: 1
>    Key_Revision: 1.0
>    Tagged_Information:
>       ModelTiepointTag (2,3):
>          0                0                0
>          6.99861111       54.0013889       0
>       ModelPixelScaleTag (1,3):
>          0.00277778       0.00277778       0
>       End_Of_Tags.
>    Keyed_Information:
>       GTModelTypeGeoKey (Short,1): ModelTypeGeographic
>       GTRasterTypeGeoKey (Short,1): RasterPixelIsArea
>       GeographicTypeGeoKey (Short,1): GCS_WGS_84
>       GeogCitationGeoKey (Ascii,6): "wgs84"
>       GeogAngularUnitsGeoKey (Short,1): Angular_Degree
>       End_Of_Keys.
>    End_Of_Geotiff.
>
>
> Thanks in advance,
> --Chandrakant
>
>
>
>
>
>
>
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