Resistograph

[Rinapea]

Hi me again and the horse chestnut tree.

Could someone explain about the resistograph? Any disadvantages?

Why would you choose the resistograph over the PICUS?

Is the resistograph only used on the stem?

Is it beneficial to do on a horsechestnut tree when decay is normally in the branches not at the root? 

Thank you

Rina 

[Khriss]

Never been keen on them. Hard to interpret and bulky to carry, not sure how they would come over in a Court with a jury ( I do use a long bit and cordless drill for decay mapping ) root and branch wood can be investigated with them , but again - bulky ! K

[Gary Prentice]

8 minutes ago, Khriss said:

Never been keen on them. Hard to interpret and bulky to carry, not sure how they would come over in a Court with a jury ( I do use a long bit and cordless drill for decay mapping ) root and branch wood can be investigated with them , but again - bulky ! K

Sorry Khriss, I'd disagree that they are hard to interpret. Have a look at some of David Humphries threads involving them. There's quite a few examples of their use in the canopy, although not so many of David aloft 

 

[Khriss]

Dunno - must be me Gary , an I am normally good with graph information ! K

[Chris at eden]

2 hours ago, Rinapea said:

Hi me again and the horse chestnut tree.

Could someone explain about the resistograph? Any disadvantages?

Why would you choose the resistograph over the PICUS?

Is the resistograph only used on the stem?

Is it beneficial to do on a horsechestnut tree when decay is normally in the branches not at the root? 

Thank you

Rina 

Its basically a micro drill which measures resistance.  So solid wood resits the drill and then when you hit decayed wood there is less resistance so the drill goes in easier.  This then shows on a graph so you can measure the thickness of the sound wall literally by measuring the graph.  Its a physical resistance test so not much scope for it to be skewed.  Unless you believe Frank Rinn that is!  You apply your own pressure to the drill button on the resitograph and Frank says that this introduces a variable.  The one his company produces has a flick switch for on and off so the pressure from the drill is more constant.  Its also a lot more expensive to buy.

 

Picus on the other hand measures time of flight of sound waves travelling through the wood and then gives you a two dimensional picture (or 3D of you do more than one scan).  This can go a bit astray sometimes and its doesn't work well on some types of decay as mentioned by Gary previously.  Picus may not always be as accurate as the resi drill but its less invasive.  There is a place for both but the appropriate one would be recommended by your VTA results. 

 

You wouldn't drill or Picus a tree just for the sake of it though, you would be investigating a defect you had already suspected or identified.  You would start with a mallet and a probe and go from there.  I inspect 1000's of trees every year and I probably recommend decay detection on two or three. 

 

           

[Nick Connell]

Normally a Resistograph is chosen over a Picus either for the application or cost.

Micro Drill - £7k
Picus - £20K

A Picus is really only useful on trees over 450mm diameter so anything less would be Microdrill territory.

Micro Drill takes about 30 seconds to set up and use with instant feedback but only a snap shot of what's going on in the tree

Picus takes about 30mins - 1hr depending on tree, measuring points, access etc but gives you more of an over view.

I've got a Picus 3 and a Micro Drill. It's best to work both together as you can do a few drills to see the best location to do the Picus. Also the results of the Picus can sometimes be misleading for many different reasons and you would need to cross check with a drill before felling a tree for instance on the strength of a tomograph.

[Stephen Blair]

Hi Nick, what courses would be needed to accurately use and interpret both the above.
Thanks

[Nick Connell]

I got my kit from Sorbus and they give you training on it. I am not sure what particular course would help in the interpretation that's really down to years of general experience of trees and understanding what the kit can do for you and like most things time on the kit.

[Chris at eden]

2 minutes ago, Stephen Blair said:

Hi Nick, what courses would be needed to accurately use and interpret both the above.
Thanks

Sorbus run a workshop for their customers that they call master classes that support, definitely the resi drill but I think also the Picus.  Its an add on to what you already do as VTA though, so competency in that is needed.  Sorbus also do re-con units if you want to pick one up on the cheap.  You can get a resi drill for £2.5k.   

 

There is an assignment on the L6 dip course which covers interpretation of decay detection equipment also as well as other bits and pieces about decay detection. 

 

   

[David Humphries]

4 hours ago, Gary Prentice said:

Sorry Khriss, I'd disagree that they are hard to interpret. Have a look at some of David Humphries threads involving them. There's quite a few examples of their use in the canopy, although not so many of David aloft 

 

Cheeky git !

I've been know to get off the ground (very) occasionally, see last image for pictoral evidence.

 

In my opinion the beauty of the microdrill (apart from the debatable invasive nature of the actual incision) is that you can use it anywhere on a tree unlike the sonic tomographs which can take a while to set up and have issues with interpretation.

We haven't got one (through choice) but occasionally bring in consultants with access to Picus and Arbotom so have had the benfits of seeing the results first hand.

With all these things, building up a portfolio of knowledge on different tree species with different decay is invaluable and the microdrills give us that experience as we often have it hand and make user of that access quite a lot.

 

Here's an article we penned for the Arb Association magazine a while back looking at interpretting  decay and dysfunction with a microdrill.