User:Ituajr/Alignment Tutorial

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Revision as of 07:10, 23 May 2020 by Ituajr (talk | contribs)
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This tutorial demonstrates the use of the Align_Overlay spreadsheet. In addition to these notes, you will need:

The steps are:

  1. Skim through Align_Overlay.txt to get an idea of what's going on
  2. Open the Align_Overlay.xlsm spreadsheet. If you get a warning "macros have been disabled", click "Enable Content".
  3. In WME, go to, which is the approximate location of the tutorial overlay
  4. Select the Image Overlays tab in WME (looks like a tiny rectangle around distant mountain ranges).
  5. In the left pane, click on "+ Add image overlay", then "choose file", and select the Tutorial_overlay.jpg file. The overlay should appear on the Waze map. You can use the "Opacity" slider in the left pane to make it translucent so you can see the obscured part of the Waze map.
  6. Identify some feature that you can find on both the Waze map and the overlay. To make it easier for this tutorial, I've marked the centre of the intersection of Milton St and Burwood Rd with a point comment "Tutorial ref A" on the Waze map, and with a red arrow near the left edge of on the overlay.
  7. In the spreadsheet, record the real coordinates of this reference point in the "Reference Points (Waze)" section of the spreadsheet. I've pre-filled this entry for you. (The coordinates for your cursor position are displayed in the lower right corner of the editor window, just to the right of the scale bars.)
  8. Record the apparent coordinates of this reference point in the "Reference Points (Overlay)" section of the spreadsheet. (Place your cursor over the reference point in the overlay, and record the coordinates shown in the map window.)
  9. Repeat for a second reference point. You could use the intersection of Shaftesbury and Milton, which I've marked with a point comment "Tutorial ref B" and a red arrow, as before.
  10. The lower half of the spreadsheet should now some initial alignment suggestions, but don't trust them yet.
  11. Repeat steps 7 and 8 for a third reference point, such as the intersection of Monash and Alexandra.
  12. In the "Adjust alignment" section, the Std Err values for Scale and Rotation should be less than 0.1. If not, go back and check your work. Start by looking for an unexpectedly large value in the Shit East or Shift North values for each row in the "Reference Points (Overlay)" section. Once the Str Err values are small enough, the "Adjust alignment" section should contain recommendations for scale and rotation.
  13. Make a note of the RMS Err figure above he "Adjust alignment" box. That gives you an idea of how close you are to a good alignment.
  14. Adjust the scale by setting the map zoom to either 2 or 10, and clicking the diagonal shrink or stretch (as appropriate) arrows in the Image Overlay controls by the suggested number of times. [If you have WME Toolbox installed, the zoom level is shown in the URL when you hover over the link symbol in the bottom right corner of the editor window. If you don't have that addin, fully zoomed in is zoom=10, fully zoomed out is zoom=0. Start at one extreme or the other, and click either "+" or "-" to step through the zoom levels.]
  15. Adjust the rotation in the appropriate direction in the same way, using the small (not 45 degree) arrows in the appropriate direction. Normally you'd use the "Number of clicks at 100% (sensitivity), but for fine adjustment, set the Sensitivity slider to 10% and use the "Clicks at 10%" count. (The Sensitivity slider can be adjusted to a precise value using the left and right arrows.) Return the slider to 100% afterwards.
  16. Ignore the Shift East and Shift North sections for the moment - they aren't accurate until the scale and rotation have been adjusted and the new coordinates have been entered into the table.
  17. Now go back and record the new lat/long figures for the apparent position of all your reference points.
  18. You should see an improvement in the RMS Err value, and the Shift East and Shift North should now be consistent.
  19. Apply the suggested East and North shifts, and follow any recommendations for adjusting scale and rotation. Then go back and update the apparent positions of all the reference points.
  20. By now, you should have a pretty good alignment of the overlay with the map - the RMS error should be less than 10 metres. Use the opacity slider to compare the overlay features with the Waze map features. You'll see that the alignment is pretty good, but is limited by the positioning of my red arrows.
  21. For better precision work, replace my original reference points one at a time with ones that can be located more precisely. For example, north-east of Tutorial ref A there's a large pink and grey building. The NE corner of that block can be located more precisely than the somewhat vague "centre of the intersection" that we first used.
  22. If you can't get consistent values or a good alignment, go back and check all your lat/long figures, and confirm that you're using the same reference points on the Waze map and the overlay. If that doesn't work, add more reference points until an outlier becomes apparent.
  23. For a real project, you would now save your aligned overlay using "Attach to map".