[mapserver-users] Matching .TFW file with EXTENT parameter?

[Robert Sanson]

Many / most GIS have a georegistration tool, that allows you to load an image requiring registration, then click on various points within the map and enter the coordinates. The system will then orient (locate and rotate if necessary) and size the image in terms of real world coordinates.
 
You will need to find such a GIS and use it (gvSIGm, ArcMap, MapInfo, TNTMips, Manifold and others), or else work it out from land features you can recognise. Do you know where the upper left corner of your image is located? Can you identify features on the image, such as street intersections? If you can measure the distance between features on your image (in terms of pixels) and the corresponding "on the ground" measurement, you will be able to work out the size of your pixels.
 
Cheers,
 
Robert S

>>> "kreshna_iceheart at yahoo.com" <kreshna_iceheart at yahoo.com> 4/11/2008 3:43 p.m. >>>
Thanks, folks. But how do I know my x-pixel resolution? And y-pixel resolution? Can it be derived from EXTENT parameters?

Thanks again,
-Kresh


--- On Mon, 11/3/08, Robert Sanson <SansonR at asurequality.com> wrote:

> From: Robert Sanson <SansonR at asurequality.com>
> Subject: Re: [mapserver-users] Matching .TFW file with EXTENT parameter?
> To: mapserver-users at lists.osgeo.org, kreshna_iceheart at yahoo.com 
> Date: Monday, November 3, 2008, 2:35 PM
> Hi Kresh
> Tiff World File (.tfw) 
> 6 rows:
> First row is x-pixel resolution (width in your coordinate
> system)
> Second and third rows are so-called "rotational
> components" but are set to zero in the case of an
> unrotated mapsheet.
> The fourth row is the y-pixel resolution (dimension in
> coordiantes). The negative sign indicates that the image
> y-axis is positive down which is the opposite from real
> world coordinates.
> The 5th and 6th rows are the Easting and Northing of the
> middle of the upper left pixel
> Robert
> 
> >>> "kreshna_iceheart at yahoo.com"
> <kreshna_iceheart at yahoo.com> 3/11/2008 8:19 p.m.
> >>>
> I have a map file with following MapExtent parameter:
>   EXTENT 106.335006 -6.896956 107.315811 -5.983994
> 
> Recently, I got a TIFF file without coordinates. I plan to
> use the TIFF file with my map. Thus, I'm supposed to
> create a .TFW file using text editor, am I correct?
> 
> Problem is: I'm not sure what parameter to be put in
> the .TFW file. Here is the parameters I put in my TFW file
> so far:
>       1.000
>       0.000
>       0.000
>      -1.000
>     106.335006
>      -5.983994
> 
> And I failed to show the raster on my map.
> 
> Please note that I am merely guessing. It seems that the
> fifth and the sixth like of the TFW should be the leftmost
> and rightmost number of my EXTENT parameter, respectively,
> but I have no idea what the first four lines are for. 
> 
> Based on EXTENT parameter above, what the correct .TFW
> values should be? Many thanks,
> 
> -Kresh
> 
> 
> 
> 
>       
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