# Coordinates of upper left corner in the world file?

According to Wikipedia and ESRI last two lines in the world file represent x and y coordinates of center of upper left pixel.

Now, if I have a world file like this:

32.0
0.0
0.0
-32.0
691200.0
4576000.0

...can I say that the "real" upper left corner of the image (upper left corner of the upper left pixel) is:

X = 691200.0 - (32.0 / 2) = 691184.0
Y = 4576000.0 - (-32 / 2) = 4576016.0

...and should I use these coordinates if I want to use the image with Bing Maps or Google Maps (after converting to Lat/Long off course), or should I stick with original ones (pixel center coordinates).

UPDATE:

I just realized that the .tab file associated with the map has coordinates of the upper left pixel (0,0) calculated the same way as in my question above. Not sure about the exact formula but resulting coordinates are the same - shifted left for half of the pixel width and up for half of the pixel height. Now I'm pretty confident that this is the right way to do it.

Yes use geographical coordinates longitude and latitude for Google/Bing Maps.

When the world file is present, ArcGIS performs the image-to-world transformation. The image-to-world transformation is a six-parameter affine transformation in the form of

The transformation parameters are stored in the world file in this order:

``````20.17541308822119 (A)
0.00000000000000  (D)
0.00000000000000  (B)
-20.17541308822119 (E)
424178.11472601280548 (C)
4313415.90726399607956 (F)
``````

The equation:

``````x1 = Ax + By + C
y1 = Dx + Ey + F
``````

where

``````x1 = calculated x-coordinate of the pixel on the map
y1 =  calculated y-coordinate of the pixel on the map
x = column number of a pixel in the image
y = row number of a pixel in the image
A = x-scale; dimension of a pixel in map units in x direction
B, D = rotation angle
C, F = translation parameters; x,y map coordinates of the center of the upper left pixel
E = negative of y-scale; dimension of a pixel in map units in y direction
``````

For Images to be overlayed with Bing Maps (MapCruncher should be used. )