Deciding what altitude to fly at is specific to the sensor you're flying with. But in general, fly lower and you get stronger ground resolution and tighter accuracy, but you also collect more data and spend more time in the field. Fly higher and you move faster, but you give up some precision.
Factors that influence altitude choice
- Sensor resolution (the higher the resolution, the higher you can fly without degrading accuracy)
- Project accuracy requirements
- Project size
- FAA Altitude Restrictions
What changes when you fly lower
- More detail per image
- Better potential accuracy
- Longer field time
- More batteries and more processing load
What changes when you fly higher
- Faster coverage
- Less field time
- Lower data volume
- Less margin for high-end accuracy, depending on the system
Practical rule: choose altitude based on the accuracy requirements and the sensor you have available.
For the majority of drone sensor combos out there, roughly 200 to 250 feet above ground is a useful middle ground. It is often the “Goldilocks zone” where crews can still get strong accuracy without over-collecting data. For projects that only require 1' contours, we generally recommend flying at 400' to reduce the data footprint and field time. For larger sensors, like the DJI Zenmuse P1, all flights should be planned at 400' unless FAA restricted since it can achieve sub 0.1' accuracy at that altitude.