► Multispectral (NIR) Principles

Use of Multispectral (NIR) Cameras in Agriculture

  • Increased use of remote sensing and photogrammetry in agriculture, forestry and natural resources management.
  • Use of satellite pictures is becoming standard management tools for both business and governmental bodies.
  • Satellites have limited to low resolution and a long time to receive them for actual analysis.
  • No valid data when clouds cover the area to be photographed.
  • Satellites have limited to low resolution and a long time to receive them for actual analysis.


No valid data when clouds cover the area to be photographed


Same area comparison of satellite image (hyperspectral) at 9 m resolution with aerial multispectral image at 0.75 m resolution.

  • Aerial imaging offers highly targeted high-resolution imaging under localized control.
  • Control of the time of day when the images are taken, not possible with satellites.
  • Pictures can be taken without cloud cover.
  • Pictures immediately available for analysis, no need to wait for satellite image.


Why use in agriculture?

Agricultural profit margins are very small, so growers have a need to maximize yield on every acre and increase productivity, leading to higher profits


How?

  • Plants have a spectral reflectivity varying widely in near Infrared (NIR) spectrum.
  • The reflectivity depends on the presence of chlorophyll and xanthophyll ? the healthier the plant, the more chlorophyll it has - the more it reflects in NIR light.
  • Using multispectral camera, enables it to separately sense green, red and NIR light levels.
  • These light levels are mathematically manipulated to produce an image that is very sensitive to crop health by using normalized differenced vegetative index (NDVI), nitrogen reflectance index (NRI) or others.


Near Infrared image obtained with Tetracam camera can indicate:

  • The amount of vegetative biomass (related to the number, size and layers of leaves)
  • Vegetative vigor (related to the thickness of the spongy layer of a leaf)
  • Greenness of the leaves (related to fertility and chlorophyll levels in a leaf)
  • The variation in this crop health index throughout the field shows areas of the healthiest crop and problem areas.
  • With this information known, efforts can be made to eliminate problems and to increase crop yields and profits.



Sample pictures of cotton crop taken days apart with a multispectral camera and NDVI surface calculated based on the pictures.


In addition data and statistics can be obtained on other agricultural information:

  • Problems with planters
  • Fertilizer spreaders or chemical application equipment
  • Irrigation system performance and uniformity
  • Plugged nozzles
  • Poorly set corner timers
  • Bad spray patterns or runoff
  • Weed
  • Insect or disease infestations
  • Variable fertility levels due to soil patterns
  • Water quality
  • Water table or soil chemistry problems
  • Results of chemical treatments or on-farm research
  • Acreage of hail or wind damage
  • Acreage of seed lots or trials
  • irrigated crop acreage for water rights and permanent records


Why Tetracam?

  • The price of acquiring the data has until now been a prohibitive factor in wide-spread adoption.
  • The size and weight of existing systems has been a limiting factor.
  • Tetracam high-resolution digital multispectral systems offer compact and cost-effective tool for the acquisition of high-resolution aerial imagery available anywhere today.
  • Camera and GPS unit (optional) constitute a complete system that can be deployed on different airborne platforms.
  • Local support in South East Asia