DRI in drone surveillance
In January 2018 you read my article regarding DRI in Video surveillance, where we made detail analysis regarding DRI (Detection, Recognition, Identification).
DRI is a
universally accepted set of standards that measure the distance at which a
sensor can produce an image of a specific target. These standards, initially
developed by the US Army in the 1950s, are often used to compare performance
between imaging cameras.
·
Detection refers to the distance at which
a target initially appears in the image. This target is something out of the
ordinary that is warmer or cooler than the ambient environment. At this
distance, there will not be enough information to confirm what the target is,
just that something is there.
·
Recognition refers to the distance at which
you can determine an object’s class (is it human, animal, or vehicle).
·
Identification refers to the distance at which
you can differentiate between objects within a class. For example, identifying
the type of vehicle (truck, SUV, or car) or whether the human is a soldier or
civilian.
How is DRI Calculated ?
DRI is
calculated using the Johnson criteria, which is based on the number of pixels
on the target. According to the Johnson criteria, the minimum resolution
required to achieve a 50% probability for an observer to discriminate an object
are:
·
Detection: an object is present – 2 pixels on
target
·
Recognition: discern the type of object, a human
vs. a vehicle – 8 pixels on target
·
Identification: discern specific objects, a man vs.
a woman, a car model – 12.8 pixels on target
These
calculations are based solely on geometrical parameters – the target size,
distance, lens focal length, and camera detector pixel size. Signal level,
detector sensitivity, atmospheric conditions, and other factors are not
considered.
Common DRI Values for Cameras and Drones
The DRI
values can vary significantly depending on the specific camera and drone
system. However, a common benchmark for a high-performance UAV (EO sensor) will
usually be in the following range:
·
Detection: Up to 10 km for a vehicle-sized
object
·
Recognition: Up to 5 km for a vehicle-sized
object
·
Identification: Up to 2 km for a vehicle-sized
object
These
values are just examples and can vary based on the specific system and
conditions.
Factors Affecting DRI:
The range
of a drone's sensor is affected by several factors, including:
·
Sensor
Technology: Different
types of sensors (e.g., EO, infrared) have varying capabilities.
·
Sensor
Resolution: Higher
resolution sensors can provide more detailed information at a greater distance.
·
Environmental
Conditions: Factors
like weather, lighting, and atmospheric conditions can impact the sensor's
performance.
·
Target
Size and Characteristics: The
size and reflectivity of the target object will influence its visibility to the
drone's sensor.
·
Flight
Altitude: Higher
altitude generally allows for a greater detection range, but also increases the
risk of interference from atmospheric conditions.
Benefits:
Crucial
for missions like ISR (Intelligence, Surveillance, and Reconnaissance), where
accurate target identification is vital.