I have found a mistake in my previous methodology; hereby a correction to
Step 3 (and following) in the document I sent out:
Attached is also a random colour table for WinDisp, qual256.clr, with a
different colour for each value from 0 - 255. (Save it into the WinDisp4
programme directory.)
Step 3 - Find centre of subset image
The Long (X) and Lat (Y) are displayed in WinDisp4 in the third box from the
left, in the status bar, and in that order (Long-Lat).
Since WinDisp4 starts numbering the lines and pixels at 0,
the centre pixel of the image is (width-1)/2 = 163 and
the centre line of the image is (height-1)/2 = 100.5
Thus, to find the exact latitude and longitude of the subset centre, which
you
will need for the conversion to Lambert, display the image (File > Open >
Image) and set the zoom to the centre of your image:
Image name: your imported subset image
Difference image name:
Colour table: qual256 (attached)
Image X1 (0=default) : 162
Image Y1 (0=default) : 99
Image X2 (0=default) : 165
Image Y2 (0=default) : 102
Maximise the window. Place the cursor in the centre of column 163 and on the
border between line 100 and 101, and read off the X-coordinate = 23.73° and
the Y-coordinate = -27.30°
Long Centre: 23.73 Lat Centre: -27.30
Step 4 - Process > Image > New
You need to create a new blank image with the correct projection (Lambert
Azimuthal) and dimensions, in order to re-project the Goode image.
Height: 202
Width: 327
Step 5 - Process > Header > Edit
Set the Header of the new image. Get Lat/Long Centre values from Step 3.
Since the subset image now becomes a reference image with the centre of the
projection at the centre of the image, the X and Y centre should be half the
width and half the height:
X Centre: 163.5 Y Centre: 101
(I am not sure whether to use the centre of the image as in Step 3 (pixel
163, line 100.5) or half the width/heigh as explained above (163.5, 101). I
have tried both and the latter matches the Africa boundary better.)
Image Type: 0, Generic
Projection: 6, Lambert Azimuthal
Height: 202
Width: 327
Latitude Centre: -27.30
Longitude Centre: 23.73
X Centre: 163.5
Y Centre: 101
DX: 8000
DY: 8000
QUAL256.clr
