The method to use in Didger to digitize a graph with multiple axes in either direction will depend if you are digitizing from a digitizing tablet or from an imported image.

Tablet Digitizing

1. Open Didger 5, click Draw | Tablet | Tablet Calibration, and calibrate the tablet using X1 and Y1.
2. Digitize the line.
3. Select the line and click Draw | Resample Polylines.
4. Choose to Resample along X direction, choose a starting, ending, and increment value, uncheck Create New Line, and click OK.
5. Once the line is resampled, click File | Export and export to a DAT file.
6. Then start a new file (File | New) and calibrate the tablet with X1 and Y2.
7. Digitize the line.
8. Resample the line using the same parameters as X1-Y1  (step 4 above)
9. Export to a DAT file. 

The X values (X1) will be the same since the lines were resampled using the same parameters. Open the two data files and copy the Y2 data into the data file containing X1 and Y1. Now you will have a data file containing X1, Y1, and Y2 data.

Image Digitizing

1. Click File | Import.
2. Select the image and click Open.
3. In the Image Registration and Warping dialog, calibrate the image using X1 and Y1 and click OK.
4. Digitize the line.
5. Select the line and click Draw | Resample Polyline (Tools | Resample Polyline in Didger 4).
6. Choose to resample along X direction, choose a starting, ending, and increment value, uncheck Create New Line, and click OK.
7. Once the line is resampled, click File | Export and export to a DAT file.
8. Select the line and delete it.
9. Select the image and click Image | Image Registration and Warping.
10. Change the Y values from Y1 to Y2 values and click OK.
11. Repeat steps 4-5 above.
12. Resample the line using the same parameters as X1-Y1  (step 6 above).
13. Export to a DAT file. 

The X values (X1) will be the same since the lines were resampled using the same parameters. Open the two data files and copy the Y2 data into the data file containing X1 and Y1. Now you will have a data file containing X1, Y1, and Y2 data.

May 1, 2018