Measure across a crack

Last update 20 Mach 2023
When measuring across a crack you might use the method with the double-point on the same ring i.e. getting a new startpoint for calculating the next ring width. Though when setting the point 25:1 above, you have to compensate for the width of the crack to make the distance between point 24 and 25:1 correspond to the actual width of the broken ring.

Using the CrackMarker tool when measuring over a crack

There is a tool in CooRecorder to measure across a crack - the CrackMarker tool.

The picture above shows two possible paths for measuring across the crack. The upper path is very precise and it is the method to be prefered when possible, i.e. the old way as described above with a pair of measuring points.

Though there are cases when you cannot traverse the crack that easy. Then the lower path may be considered!

When using the CrackMarker tool you can set a crackmark point at each side of the crack as shown above. When CDendro reads the .pos file, it will subtract the width of the crack from the full width of the ring.

The main problem with this method is that it is difficult to see the edges of the crack as the scanner does not look in right angles towards the wood surface. Instead this picture was obviously taken aslant, as it shows a bit of the inside of that crack as a light area.

To use the CrackMarker tool, click on its button and it will light up. You can also select it with the M key on your keyboard. Then click where you want to set the points. When ready, click e.g. the D key (data mode) to continue measuring as normal.

You may set a single crackmark in front of a ring border as shown above. You may do so also in front of a W-point at a latewood/earlywood border. There is no limit for the number of crackmarks within the same ring but they have to be on a straight line to make the measurements correct - see the tooltip in the following image (from CooR version 9.3)!

Better precision when setting M (crackMarker, %gap) commands

  • CrackMarker (M): Use Ctrl-Click to place a new crackmarker point and make it snap to an imaginable line between the two adjacent yearly border (latewood) points.

Extensive use of start-point shifting

Here is an example of a sample that has been heavily eaten up by the house longhorn beetle. The trunc is in the Sandviken house at Västanvik, Nämdö and was sampled by Lars Löfstrand in 1994.

The picture demonstrates how you can again and again shift the starting point when measuring a next ring width.

Note: The circle around point 10 is there only to demonstrate how you by clicking on the "Show selected" button easily can get a connection between a point on the sample and the corresponding points (1738) on the curves.
As the samle is displayed with older rings towards the right, the curves have been displayed the same way. (A user can change that with the Times button.)



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