Counting Trees | Every Credit Has A Story
Kyle Nielsen, Acorn's Innovation Consultant and native Zimbabwean, met a variety of smallholder farmers connected to our mission and activities. In a series of travel blogs, he shares their stories and his experiences. Previously, he introduced us to farmers Grace and Mathew. This time, he explains just what ground truthing actually entails.
Counting trees: how hard can it be?
After an hour of clambering up dusty roads (read: large footpath), our tiny 2004 Suzuki Swift had finally reached the farmer we had been looking for, James. We stepped out, greeted the team, and then finally appreciated our daring ascent.
Standing atop one of the many rolling hills in the Nandi County of Kenya, we peered into the valley of some 4000 smallholder coffee farmers. And the best part? We had only just begun the ground truth exercise.
Ground truthing (or field data collection) is the general term we call our in situ data collections. Enumerators or data collectors are tasked with collecting tree samples according to our methodology.
In general, we need to know what trees have been planted and how large they are. In a one-hectare area, the enumerators measure the height and diameter amongst other characteristics of all the trees above 1.3 meters in height. (Exact information on the procedures is included in our methodology.)
Why do we do ground truthing?
The field data is converted into biomass values and used as input for our monitoring algorithms. In essence, the models need to learn how much biomass to associate with the pixels so that we can estimate the biomass present on other farms that are included in Acorn. (More comprehensive information can be found here.)
On paper, all a simple exercise. Go out, take some measuring tapes, count some trees, and job done.
Ghana. 37 degrees and hours away from the nearest town. After a full morning, we still had half the farm to go when we faced ‘the great wall’ of grass. The enumerators looked at me, and before the question came, I answered. Yes, we have to go through it.
We needed to complete the one-hectare area. Our tape measure disappeared mere metres in front of us. We reverted to shouting for one another like giant bats in the middle of a field.
To escape the heat, (and let the itching subside for a while) we sat down for lunch under a beautiful tree on a perfect patch of green grass. Halfway through tucking into my lunch of spicy rice and a fish head, I became the unintended meal for a nest of fire ants.
So, how hard can it be to count a tree?
The foreboding wall of grass