Forest mensuration (measuring trees and forests) has come of age. I have written a few posts about forest mensuration and also how to use a smartphone to measure tree height – see links below. I recently came across some really impressive apps for use by foresters and woodland owners to measure trees and areas, and to calculate stand basal area, using an iPhone smartphone.
The Relascope (Spiegelrelaskop), invented by Austrian forester Walter Bitterlich (1908-2008), is a specialist and expensive instrument used by foresters to estimating tree height, distance to tree (although this is complicated), and the basal area of a stand (the sum of the cross-sectional area of trees, taken as a dbh and calculated inside the bark). Although a superb instrument and highly accurate in trained hands, the Spiegelrelaskop is not likely to be used by many private woodland owners as it is unaffordable to many (£1500/$2400). Other relascope types are available, see How to use a wedge prism relascope to measure basal area, but the development of powerful forest mensuration tools for smartphones, which most people carry today, is very welcome.
The apps that I’ve been trying are available free from the Apple app store, developed by Taakkumn Watakushi from Fukushima in Japan. I have no hesitation in recommending these two apps as I’m not aware of anything else like these that are available for foresters. He also provides a compass surveying app (iCompass Surveying) that enables areas to be measured but I have not tested it.
The iHypsometer is a free (in the ‘Lite’ version) tool for estimating tree height. It works on the same principles of trigonometry that I explained in How to measure tree height using a smartphone but it copes with sloping ground (i.e. when the base of tree is not level with your feet) and it completes all the tricky maths for you. It requires that you have a ‘friend’, whose height you should measure, and who should stand next to the tree, although I find that a stick cut to a suitable height works just as well. Angle measurement works in the same way as I described in How to measure tree height using a smartphone except that it uses the short side of the phone. The only feature that I would like the developer to improve is to use the longer side of the phone for sighting along, as I have found in other apps that this provides much greater accuracy.
The iBitterlich is a free app for calculating forest stand basal area. It uses the view from the camera on an iTouch (latest model)/iPhone 3G and up/iPad, on which it overlays buttons where the number of trees of different categories of dbh can be counted simply by pressing them. In the screenshot (below) I was looking at the second tree that I had counted as a ‘+3’, and I had already counted 4x ‘+2’ and 11x ‘+1’ trees in my sweep, that at this point was almost complete at 320 degrees.
After finishing a 360 degree sweep of the forest stand and counting all the trees, the average tree height is entered in another field, and form factor can be adjusted. The stand volume m3/ha and basal m3/ha are then displayed at the top of the screen. Visit the iTunes app store to download iBitterlich
Have you tried these apps in the forest and did they work for you? Are you aware of similar apps from other developers? Is there a similar set of apps for the Android platform? Do let me and readers know by sharing your views via a comment.
Other posts about forest mensuration