Measurement Guide & Protocols

Official measurement protocols for The Great Baobab Quest. All participants must follow these standards to ensure fair and scientifically valid competition entries.

Official ProtocolResilient Earth Nigeria

CBH Height

1.3 m

Above ground level

Primary Metric

CBH

Circumference at Breast Height

Age Formula

0.213 × CBH(cm)

Estimated years

Primary Measurement: Circumference at Breast Height (CBH)Most Important

CBH is the primary ranking criterion. It must be measured at exactly 1.3 metres (130 centimetres) above the ground on the uphill side of the tree. This is the internationally accepted standard for measuring tree girth, known as "Diameter at Breast Height" (DBH) in forestry science.

1

Locate the Measurement Point

Stand on the uphill side of the tree. Using a measuring tape or stick, measure 1.3 metres (130 cm) vertically up from the ground at the base of the trunk. Mark this point clearly — this is your "breast height" measurement point.

If the tree has buttress roots, swellings, or branches below 1.3m, measure above these features at the narrowest point above the irregularity, and note this in your submission.

2

Wrap the Measuring Tape

Using a flexible, non-stretch measuring tape (a tailor's tape or forester's tape is ideal), wrap it horizontally around the entire circumference of the trunk at the marked 1.3m point. Ensure the tape is:

Pulled snug but not compressing the bark
Perfectly horizontal (level) all the way around
Not twisted or angled at any point

3

Record the Measurement

Read the measurement where the tape meets itself. Record the value in metres and centimetres (e.g., 8.45 m or 845 cm). Enter this as the CBH in your submission form.

The Diameter at Breast Height (DBH) can be calculated as: DBH = CBH ÷ π (approximately CBH ÷ 3.14159)

4

Photograph the Measurement

Take a clear photograph showing the measuring tape wrapped around the trunk at the 1.3m point. The tape reading must be clearly visible in the photo. This is a required photograph for your submission.

Secondary Measurement: Total Tree Height

Height is a secondary metric used as a tie-breaker. Estimate the vertical distance from the ground to the highest point of the canopy.

Shadow Method

On a sunny day, measure the length of the tree's shadow and the length of your own shadow. Calculate: Tree Height = (Tree Shadow ÷ Your Shadow) × Your Height.

Stick Method

Hold a stick vertically at arm's length. Walk back until the stick appears to equal the tree's height. The distance from you to the tree equals the tree's height.

Secondary Measurement: Crown Spread

Crown spread measures the horizontal diameter of the canopy — an indicator of tree maturity and health.

1

Find the Widest Points

Walk around the tree and identify the two points where the canopy extends furthest from the trunk in opposite directions.

2

Measure the Diameter

Measure the distance between the two outermost canopy edges in a straight line through the centre of the tree's canopy projection on the ground. Record in metres.

Health Assessment (1–5 Scale)

Score	Crown Density	Structural Integrity	Overall Vitality
1	Very sparse, <20% foliage	Severe decay/damage, collapse risk	Dying or dead sections
2	Sparse, 20–40% foliage	Significant damage or cavities	Declining, poor growth
3	Moderate, 40–60% foliage	Some minor damage, stable	Average health
4	Dense, 60–80% foliage	Minor blemishes only	Good health, active growth
5	Very dense, >80% foliage	No visible damage	Excellent, vigorous growth

Required Photographs

Photo 1

Full Tree Shot

Step back far enough to capture the entire tree from base to crown tip. The full canopy and trunk must be visible. Use landscape orientation if possible.

Photo 2

Trunk Measurement

Photograph the measuring tape wrapped around the trunk at the 1.3m mark. The tape reading must be clearly legible. Include a marker at the 1.3m point if possible.

Photo 3

Participant Scale Reference

Stand directly next to the trunk and have someone photograph you with the tree. This provides a human scale reference for verification purposes.

Recording GPS Coordinates

GPS coordinates are essential for verification. Stand at the base of the tree and record your coordinates using your smartphone's GPS or a dedicated GPS device.

Using a Smartphone

Open Google Maps, press and hold on your location to drop a pin, then read the coordinates shown at the bottom of the screen. Enter Latitude first, then Longitude.

Coordinate Format

Enter coordinates in decimal degrees format (e.g., Latitude: 12.0022, Longitude: 8.5920). Northwest Nigeria coordinates are typically between 10°–14°N and 3°–13°E.

Estimating Tree Age from CBH

Formula: Estimated Age (years) = 0.213 × CBH (in centimetres)

This formula is based on the average annual growth rate of African Baobabs. The system calculates this automatically from your CBH entry.

CBH (metres)	CBH (cm)	Estimated Age	Classification
2.0 m	200 cm	~43 years	Young adult
5.0 m	500 cm	~107 years	Mature
10.0 m	1000 cm	~213 years	Old growth
15.0 m	1500 cm	~320 years	Ancient
20.0 m	2000 cm	~426 years	Exceptional
25.0+ m	2500+ cm	~500+ years	Heritage specimen