Environmental impact is a claim about change caused by a project. To make it stand up, you need to know what the land was like before the project touched it — and that "before" is the one thing a field team can never go back and collect once the ground is disturbed. The open satellite archive can, and that is what makes it the most valuable baseline dataset most assessments never use properly.
Why "before" is the whole assessment
An impact assessment lives or dies on attribution: can you show that a change on the ground was caused by the development, and not by the drought that year, a veld fire, or a trend that was already underway? You cannot answer that without a credible pre-disturbance baseline to measure against. A monitoring programme that starts the day construction does has nothing to compare to — every later reading is a number with no reference, and "the vegetation declined" becomes impossible to separate from "it was always going to be a dry year."
The baseline you can't collect later
This is where the archive is irreplaceable. Field surveys and drone flights can only ever record the present; once a site is cleared, its earlier condition is gone from the ground. But Sentinel-2 has imaged most of the country every few days at 10 m since 2015, and the Landsat record stretches back decades at coarser resolution. That means a baseline can be reconstructed for the years before the application — land cover, vegetation extent and condition, seasonal patterns — even when a specialist is brought onto the project late. You cannot create this data after the fact at any price; it either sits in the archive already, or it is lost. Capturing it early is the cheapest insurance an assessment can buy.
A baseline is a range, not a snapshot
A single pre-project image is almost as misleading as none. Vegetation condition swings with rainfall, season and fire, so one scene captures one moment in a naturally moving system. A defensible baseline characterises the envelope of natural variability — how far the site's condition ranged across the seasons and years before disturbance. That envelope is what later lets you say something useful: that a post-project change falls outside normal fluctuation and warrants attention, or that it sits comfortably within the range the site always moved through. Without the range, every later reading is argued in a vacuum.
What it sets up for the life of the project
A baseline built this way is not a once-off deliverable filed with the application. It is the fixed reference the whole monitoring programme is measured against — construction phase, operation, and eventually rehabilitation and closure. Because every later observation is compared to the same documented pre-disturbance record, measured the same way, the assessment carries a consistent evidence trail from before the first machine arrived to the day the liability is signed off.
Where the line sits
TerraX supplies and stands behind the remote-sensing baseline and its method — land cover, vegetation condition, change history and the range of natural variability, with its uncertainty stated and its limits (resolution, cloud, what the sensor can and cannot resolve) made explicit. The ecological interpretation, the significance of any impact, and the professional sign-off on the EIA remain with your registered practitioners. Satellite data describes condition and change; it does not, on its own, assign ecological meaning or cause — that is where the ground ecology and the registered assessor come in.
If a specialist layer is worth having on a project, it is worth having before the ground changes. That is the core of our environmental baseline service — tell us the study area and the deadline, and we will reconstruct the before while it is still in the archive.