Multispectral Ground Calibration




The radiation that is reflected from any subject under observation varies with factors that are independent of that subject.   These include properties of the atmosphere, the time of day they were imaged, latitude, etc.  If the multi-spectral imaging system does not take these factors into account during image processing, the wavelengths reflected by a subject that are represented in the image will differ from those that would be represented under other more nominal conditions.  Multispectral Ground Calibration Targets help users standardize representation of the reflected radiation from a given subject under varying light conditions.

Multispectral Ground Calibration Targets provide a relatively flat response to incident radiation throughout the VIS-NIR wavelengths monitored by Tetracam cameras.  Placed in the camera’s field of view, the known reflectance values of a Multispectral Ground Calibration Target may be used as a standard to provide calibration correction factors.  These enable Tetracam systems to compensate for lighting conditions that would otherwise skew image results.  Precisely positioned Ground Calibration Targets may also be used to help geo-reference image mosaics.  In addition, these targets may be used to correlate imaging results obtained from a variety of different remote sensing systems. 

The Ground Calibration Targets are fabricated from highly durable Type 822 Woven Polyester fabric.  Targets may be staked down to the ground through grommets stitched into the targets.  Staking targets insures they lie flat and that they stay in place. These targets have been sold to a wide range of customers including NASA, USDA, DoD, Monsanto and numerous farms and universities located throughout the world.  Targets range from 1.2 meters to 20 meters in size.  The optimum size selected by the user will depend upon the pixel sampling needed to satisfy calibration statistics.  The neutral grayscale band average reflectivity of each target ranges from 3% to 82%.   The percentage is selected so images do not appear over- or under-saturated.  Lower values show details in shade.  Higher values would be selected for bright lighting conditions.  Grayscale values from 6% to 48*% are the most common selections for nominal lighting conditions.


Target Construction: Fabrication Notes

Ultrasonic tacking with sewn seams and hems

Stitch type: Double needle lockstitch - background seam and hems

Single needle lockstitch - resolution elements or patterns

Thread: Polyester thread color approximates reflectivity level

Web seam overlap: 1 inch (25mm)

Panel hem width: 2 inch, (50mm) double fold

Hold-down: Grommets on approximate 1m centers (dependent upon panel dimensions)

Edge grommets: #4 black brass rolled rim claw grip


Multispectral Ground Calibration Target Pricing

Target Panel Outside Dimension* Fabric Webs / Panel Standard Price /Panel
1.2 x 1.2 meter 1 web, 0 seams $940.00
3 x 3 meter 2½ webs, 2 seams $1,480.00
3.6 x 3.6 meter 3 webs, 2 seams $2,140.00
4.3 x 4.3 meter 3½ webs, 3 seams $3,050.00
5 x 5 meter 4 webs , 3 seams $4,255.00
6 x 6 meter 5 webs, 4 seams $5,940.00
8 x 8 meter 6 webs , 5 seams $10,560.00
9 x 9 meter  7 webs, 6 seams $13,365.00
10 x 10 meter 8 webs, 7 seams $15,900.00
* Final panel size taking in account one 1" web-to-web seam overlaps and 2" wide double fold hems.
Standard gray scale reflectance levels: 3%, 6%, 12%, 24%, 36%, 48%, 56%, max white 82%
Custom reflectance levels and color panels may be coated based upon requirements
Discrete wavelength calibration panels available for HSI Systems - request quotation
Resolution Target Arrays (Tri-Bar, Edge, Siemens Star, Custom Patterns) - request quotation
R10 Target Stakes: $6.00 each as of July 2013

Price includes: 
Ground calibration panel of indicated dimension 
Target instruction manual with initial spectral reflectance data 
Repair fabric
Prices do not include shipping and handling charges.  
Prices are subject to change without notice.
Depending upon the size and number of panels ordered, nominally 1 to 2 weeks ARO.





Smart NDVI cameras are multispectral cameras for precision agriculture that can calculate vegetation indices and create false color NDVI images without the use of an image processing program accessory.

Precision Farming and Forestry need multispectral camera and NDVI camera images to create orthomosaic maps that allow interventions to be optimized. NDVI phenocameras that can perform time lapse photography are best for slow growing flora, while faster growing commercial harvests are best served by airborne NDVI mapping cameras.