Glossary
Prescription Map
A georeferenced map that divides a field into zones and assigns each zone a target application rate — the file a drone or floater follows to run a variable-rate job.
Definition
A prescription map (often called an "Rx" or VRA map) is built by combining data layers — NDVI imagery, historical yield maps, soil-test grids, elevation, and EC scans — into a set of management zones, then assigning each zone a rate. The map is exported as a shapefile or controller-specific format and loaded into the application equipment. During the job, GNSS tells the machine which zone it is over and the rate changes automatically. The quality of the prescription depends entirely on the quality and honesty of the underlying data layers.
In an Alberta Context
For an Alberta grower, the most accessible starting layer is a current-season drone NDVI flight, which can be flown over a quarter in well under half an hour and turned into zones the same week. Layering that against last year’s yield-monitor data and a soil test produces a prescription that reflects the actual variability of the field rather than a generic textbook rate. NDVI on its own shows vigour, not nutrient need — ground-truth it with soil and yield data before committing rates. In Canada today these prescriptions drive granular spreading (fertilizer, seed) by drone. Liquid pesticide application by drone is a separate matter, now under a narrow interim pathway following PMRA’s June 2026 Letter of No Objection.
Why It Matters
The prescription map is the bridge between sensing and doing. A drone NDVI flight that just produces a pretty picture changes nothing; turned into a prescription map and flown as a variable-rate spread, it changes where the fertilizer lands and what the field returns. It is also the documentation trail that supports VRA claims for funding and sustainability programs.
Frequently Asked Questions
+Who builds the prescription map — UAV AG or my agronomist?
Either. Many growers have their agronomist assign the rates; UAV AG can fly the NDVI layer and assemble the zones, then your agronomist signs off on the rates. What we always do is confirm the final Rx file loads cleanly into the spreader before the job.
+What data do I need to send to get a draft prescription?
The most useful inputs are last year’s yield map, a recent soil test, and field boundaries. With those plus a current NDVI flight we can draft management zones; rates are set with your agronomist.
+What file format should a prescription map be in?
A shapefile is the most widely compatible; some controllers also read GeoTIFF or GeoJSON. Send what you have and we will confirm compatibility for the DJI Agras spreading job.
+Does the drone record what it actually applied?
Yes — an as-applied log of where product landed and at what rate is captured for your records and for any funding or 4R documentation.