Image data can also be acquired from multispectral scanners or radar sensors aboard aircraft, as well as satellites. This is useful if there is not time to wait for the next satellite to pass over a particular area, or if it is necessary to achieve a specific spatial or spectral resolution that cannot be attained with satellite sensors.
For example, this type of data can be beneficial in the event of a natural or man-made disaster, because there is more control over when and where the data are gathered.
Common types of airborne image data are:
- Airborne Synthetic Aperture Radar (AIRSAR)
- Airborne Visible/Infrared Imaging Spectrometer (AVIRIS)
- LIDAR (Light Detection and Ranging)
Aircraft Radar Imagery
AIRSAR was an experimental airborne radar sensor developed by JPL, Pasadena, California, under a contract with NASA. AIRSAR mission extended from 1988 to 2004. AIRSAR was an imaging tool mounted aboard a modified NASA DC-8 aircraft.
This sensor collected data at three frequencies:
Because this sensor measured at three different wavelengths, different scales of surface roughness were obtained. AIRSAR sensor had an IFOV of 10 m and a swath width of 12 km.
AIRSAR data have been used in many applications such as measuring snow wetness, classifying vegetation, and estimating soil moisture.
Aircraft Optical Imagery
AVIRIS was also developed by JPL under a contract with NASA. AVIRIS data have been available since 1992.
This sensor produces multispectral data that have 224 narrow bands. These bands are 10 nm wide and cover the spectral range of .4 - 2.4 nm. Swath width is 11 km, and spatial resolution is 20 m. This sensor is flown at an altitude of approximately 20 km. Data are recorded at 10-bit radiometric resolution.
Daedalus is a thematic mapper simulator (TMS), which simulates the characteristics, such as spatial and radiometric, of the TM sensor on Landsat spacecraft.
Daedalus TMS orbits at 65,000 feet, and has a ground resolution of 25 meters. Total scan angle is 43 degrees, and swath width is 15.6 km. Daedalus TMS is flown aboard the NASA ER-2 aircraft.
Daedalus TMS spectral bands are as follows:
Daedalus TMS Characteristics
0.42 to 0.45
0.45 to 0.52
0.52 to 0.60
0.60 to 0.62
0.63 to 0.69
0.69 to 0.75
0.76 to 0.90
0.91 to 1.05
1.55 to 1.75
2.08 to 2.35
8.5 to 14.0 low gain
8.5 to 14.0 high gain
Leica Geosystems ADS80 is a pushbroom airborne digital sensor providing co-registered imagery in equal resolution in panchromatic, RGB color, and Near-Infrared spectral ranges. ADS80 supports a wide range of geospatial mapping applications, such as large-area orthophoto generation, remote sensing and highly accurate DSM generation.
Source: Leica Geosystems ADS80, 2012.
National Agriculture Imagery Program (NAIP) acquires aerial imagery during agricultural growing seasons in the continental United States. NAIP collects leaf-on (as opposed to the more common leaf-off) aerial imagery. This imagery is used for estimating crop plantings and yields. NAIP is administered by Unites States Department of Agriculture (USDA) Farm Service Agency (FSA) by the Aerial Photography Field Office.
NAIP imagery has a 1 meter ground sample distance (GSD) with a horizontal accuracy that matches within six meters of photo-identifiable ground control points.
NAIP imagery typically places wavelengths in this order: Red, Green, Blue, Near Infrared.
NAIP Bands and Frequencies
When using Indices dialog in ERDAS IMAGINE, these wavelengths are derived based on Leica ADS40 airborne scanner, a commonly used system for generating NAIP imagery.
If a different camera was used to acquire the NAIP, then wavelengths may need to be adjusted accordingly.