Guide · July 2026
How height classification measures what is growing on your land, band by band, and turns a nagging suspicion about encroachment into a number you can budget, plan and act on.
Ask any farmer whether the veld is getting bushier and the answer is yes. Ask by how much, over how many hectares, and how fast, and it becomes a shrug and a gesture at the horizon.
That gap matters. Bush encroachment advances slowly enough that nobody notices from the bakkie until a great deal of grazing has been lost — and you cannot budget against an impression, plan clearing against one, price a property with one, or prove to a bank that the land is improving.
From a single survey flight, with no additional visit and no extra sensor: a map of how tall everything growing on the property is, divided into height bands; the hectares and percentage in each band; a summary of how much of the farm is genuinely open and producing grass; the extent of the browse layer; and, where a previous survey exists, exactly which blocks improved and which went backwards.
Every one of those is a figure in a table and a layer in a GIS file.
The survey produces a surface model — the height of the top of everything — and a terrain model of the bare earth beneath. Subtract one from the other and what remains is the height of whatever is standing there. That is a canopy height model, and it is the basis of all vegetation analysis.
The canopy height model is continuous — every cell carries a height in metres. To be useful it is divided into bands and the area within each calculated. A typical classification for South African grazing land runs from bare ground and short grass, through standing grass, low scrub and seedling encroachment, into established shrub at browsing height, small trees, and mature canopy above six metres.
The bands are configurable rather than fixed. A cattle operation cares about where grass gives way to shrub. A game operation cares about the browse layer between roughly one and a half and three metres. A forestry assessment cares about the upper classes. They should be set to the questions your property needs answered.
The output is a colour-coded map plus a table of hectares and percentages — and the table is usually the part owners find genuinely new.
Quantify encroachment, with a real number: this many hectares under woody vegetation above a given height, that many still open grassland, as a percentage of the property.
Assess real grazing capacity. Carrying capacity assumes grass. Knowing how much of the farm is genuinely open turns that from an assumption into a measurement.
Separate browse from graze. On a game property the browse band directly informs which species the land supports and in what numbers.
Plan and price clearing. Clearing is expensive and rarely affordable all at once. A height map shows where encroachment is worst, where it is still light enough to be cheap to reverse, and lets a multi-year programme be costed and sequenced rather than guessed.
And prove change over time — which is the most valuable use of all. Two surveys, a year or two apart, show precisely which blocks improved and by how many hectares. That is evidence for a buyer, a bank, a lessee or a conservation authority, and it is how good management demonstrates itself.
Large areas of South African savanna and grassland have thickened over recent decades, with the usual suspects including sickle bush and blackthorn in the bushveld and, in the drier west, invasive Prosopis. Grass production falls on land that looks superficially healthy.
Light encroachment is inexpensive to reverse. Established thicket is not. Knowing where a property sits on that curve, block by block, is what makes the difference financially — and it is precisely what an impression cannot tell you.
There are legal dimensions too. South African legislation places duties on landowners regarding declared invasive and alien species, principally under the National Environmental Management: Biodiversity Act and its regulations, alongside obligations under the Conservation of Agricultural Resources Act. Requirements differ by species and province, so specifics belong with an extension officer or an attorney — but a height map quantifies the extent of woody cover, which is where any such assessment starts.
Height classification performs strongly across the conditions most South African grazing land presents: open veld, scattered bush and moderate encroachment, where the ground is visible between vegetation and heights are measured directly.
Where thicket closes over completely, the survey continues to map extent and structure accurately while heights within those blocks are best read as indicative. A good report identifies which blocks fall into which category — and in practice those dense blocks are usually already known to the owner as the ones needing attention.
Height classification measures structure rather than species. Pairing it with your own knowledge of the property, captured during the site walk, is what turns a structural map into a management plan.
Comparisons should be flown at the same time of year, because deciduous bush changes substantially between summer and winter and like-for-like timing is what makes a comparison meaningful. The season flown is recorded as part of the report.
Calm conditions and a higher sun angle both improve the result. And it is worth establishing the baseline early — the first survey is valuable even if nothing is done with it immediately, because it is what every future comparison measures against.
A colour-coded vegetation height map as a GeoTIFF and as a presentation image, the class area table in hectares and percentages, the underlying canopy height model so bands can be recalculated later without re-flying, an open-versus-woody summary, change comparison where a previous survey exists, the surface and terrain models behind it, and a statement of method, class definitions and the season flown.
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