Precision Agriculture, Crop Mapping, and more
In the past few weeks I have had more than one conversation with people wanting to use small electric rotary wing systems (quads, hexacopters etc) for crop mapping. In more than one instance people have become upset with me when I inform them that these airframes with their relatively low endurance are not suited for mapping ten thousand hectares of sugarcane in central Guatemala.
Depending on weather conditions, payload, battery, airframe etc you can only reasonably expect 15 minutes of flight time out of most commercially available systems. With these types of times the most you will be able to map is about 20 acres an hour with multiple battery changes. The purple lines above represent the “lawnmower” pattern required to capture NADIR imagery and depending on the size of the field can represent a flight path of dozens of miles.
Another aspect is regulation. Visual Line of Sight of VLOS is a really important safety principle. If you are operating your systems out of visual line of sight you really need to be confidant in that system and willing to pay the price if things go wrong and you cannot take manual control of the unit. The above image gives you a rough idea of the size of the aircraft and how much area you can cover while keeping small UAS in sight, and yes I have “pushed” the boundaries somewhat as in practice a lot of the time you simply loose track of the system and have to rely on telemetry on your GCS to know where the unit is.
This leads me to my next statement. Unless you are crop mapping an entire field, test plot etc it makes no commercial sense whatsoever in my opinion to put a NIR camera on a quadcopter. I stand to be corrected but if you want to create NDVI data sets what is the point of only capturing a small percentage of a field and then looking for patterns in that?
So what are small electric multi rotors good for. They are great for small scale mapping (dozens of acres) and for crop scouting. That is taking simple still and video imagery quickly and efficiently. if you want to map crops you need to look at fixed wing solutions with all their inherent issues and GIS processing challenges.