Multispectral Imagery refers to images which contain color bands beyond the normal R,G,B values. Camera sensors are able to collect light waves that are beyond human eye perception, and these are processed into additional color bands contained as part of the aerial or satellite image. Near-infrared is a common fourth band used for vegetation analysis, and is available from multiple sources for North Carolina.
In 2011, the Working Group for Orthophotography Planning, a sub-committee of the NC GICC, produced "Using Color Infrared Imagery" (PDF). This is a guide for understanding, interpreting and benefitting from color infrared imagery. The paper provides technical insight into CIR imagery and the many useful appliations that it serves.
The NAIP statewide aerial photos contain a near-infrared fourth band. These images are:
- often referred to as color-infrared, or CIR
- in uncompressed GeoTIFF format
- tiled to the same tilling system as previous USGS DOQQ products
- 1 meter resolution
- in UTM projection
- available for public download. TIFFs for only the latest year are in this location. Contact Data Services for prior years or if you need a large number of tiles.
For more information about NAIP imagery, see the NCSU Libraries' NAIP webpage.
An online video here demonstrates how to use CIR NAIP imagery in ArcMap. In brief, under the Layer Properties, Symbology tab, change the Channels to: Red-Layer_4, Green-Layer_1, Blue-Layer_2, Stretch Type-Standard Deviation, n: 2.
2010 Statewide Orthophotos
In the Winter and Spring of 2010, orthophotography was collected for the entire state of North Carolina at a 6-inch resolution from funding provided by the NC 911 Board so that the imagery would be available for emergency dispatchers and responders. Further information is available from the NCGICC website.
Processing of the natural color bands of this imagery has been funded by the 911 Board. However, the infrared band was also collected by the cameras, but processing has not been funded, except for Wake County. The Wake County 4-band TIFF images are on the Geodata Server under /localgov/Wake_County/2010_ORTHOS/CIR2010/.