GIS users often use imagery to capture data. Most users are familiar with the spatial resolution of a sensor being defined by a measure called GSD (Ground Spatial Distance) or pixel size, eg. 50cm resolution is better than 1m resolution. 50cm is considered “higher resolution” as more detail is visible.
However there are other terms used in remote sensing that users should be aware of – specifically Recognition and Identification.
Detection = red object
Recognition = red vehicle
We cannot tell if this is a ute or sedan so Identification is not possible yet.
Identification = red sedan
As resolution improves cost goes up, so it is important to determine the purpose of the imagery Identification versus Recognition. In the above examples above do we need to count cars in the carpark (Recognition) or do we need to know what type of vehicle they are (Identification)?
Guidelines for Detection, Recognition and Identification
Detection = object size/3 = GSD – eg. car 5m/3 = 1.5 – 1.6m GSD required to Detect
Recognition = object size/10 = GSD – eg. car 5m/10 = 0.4 – 0.5m GSD required to recognise
Identification = object size/21 = GSD – eg. car 5m/21 = 0.1 – 0.2m GSD required to identify