Remote sensing can be defined as the science, art and technology of obtaining reliable information about earth objects, area or any phenomenon through the analysis of data acquired by a device (sensor) that is not in physical contact with the phenomenon under investigation.
The major objective of remote sensors is to detect and record energy in a selected portion of the electromagnetic (EM) spectrum, the detection is made possible because of TON/colour enhancing contrast between object or phenomenon of interest and its back ground.
The development of remote sensing technology have had a profound reflection on many human activities in some of this activities, new concept have being given confirmation also new perspective have been open to scientist.
Generally speaking, in remote sensing recording and acquisition of data and information of some properties of object or phenomenon are carried out through the use of instrument either stationery or on board mobile plat form.
Remote sensing techniques have find its application in the following fields geology, mineral resources, fisheries, Agriculture, soil mapping, land use/cover mapping, range land, water bodies, wildlife ecology, environmental assessment, and forestry (tree species identification, timber cruising, forest damage assessment, monitoring logging and reforestation, forest land appraisal, timber harvest planning and assessing application of herbicides and fertilizer In forest stands, assessing plant vigor and health in forest nursery).
TYPES OF REMOTE SENSORS
There are two  types of remote sensors.
Passive remote sensor
Active remote sensor
PASSIVE REMOTE SENSOR: these are sensors which make use of natural radiation either reflected or emitted from the earth. They do not emit energy but simply detect energy that is reflected or propagated back to the sensing device. E.g, the human eye, ear and photographic camera used without flash.
The eye detects energy in the visible portion of the electromagnetic spectrum while the ear detects sound energy. The photographic camera used in daylight without flash is a passive remote sensor.
ACTIVE REMOTE SENSORS: these are sensors that produce their own electromagnetic radiation. They emit energy to the target under investigation and collect the reflected emittions E.g LIDAR, RADAR and photographic camera used with flash
STAGES IN REMOTE SENSING PROCESS
Two stages are involves in remote sensing.
() Data collection:- This stage involves the use of sensors to acquire data on photographic film or as digital data.
(2) Data analysis: – This stage involves the critical interpretation of data collected by sensors in order to provide meaningful information. This may be visual interpretation (airphotos) or digital analysis (satellite imagery).