Which accuracy can I achieve?

When we speak about ‘accuracy’, we need to make a distinction between ‘absolute accuracy’ and ‘relative accuracy’.

Absolute accuracy is the error on the coordinates of a point in the orthophoto with respect to the same point on a map or as measured by a landsurveyor.

Relative accuracy is the error on the measured distance between two points in the orthophoto. This impacts surfaces, distances and angles that you measure in the orthophoto.

Are you mainly interested in surfaces ? (for example for a new patio or lawn) and distances with respect to a house, you can use a DJI MINI 2. The relative accuracy of the result will be around a centimeter. The absolute accuracy can be a few meters because the MINI2 doesn’t have an accurate GPS on board. For example, you’ll measure the size of a 60×60 tile exactly, but the coordinates will deviate from what a landsurveyor will measure.

Also for measuring roofs or to get an idea of the volume of a pile of soil, the relative accuracy obtained with a MINI2 is sufficient.

Do you need a better absolute accuracy ? Than we recommend to use a Phantom 4 RTK, with or without ground control points. With the images taken with a Phantom4 RTK, the expected absolute accuracy will be below 5cm. Combined with 2-3 ground controle points, it is possible to get 1-3cm.