The ASD FieldSpec 4 Hi-Res NG spectroradiometer

The ASD FieldSpec 4 Hi-Res NG provides enhanced spectral resolution to support accurate calibration and image classification analysis.

Higher resolution hyperspectral sensors yield greater precision for remote sensing classification applications, producing more information from every pixel generated in an image than ever before. In order to take advantage of the full potential of these sensors, measurements from ground-based instrumentation need to meet or exceed the sensor’s spectral resolution. In the absence of this resolution equality, data are interpolated during post-processing; as a result, vital spectral information can be smoothed and lost.

The enhanced spectral resolution of the FieldSpec 4 Hi-Res NG meets the rigorous demands of hyperspectral imaging systems such as AVIRIS-NG and HySpex ODIN-1024. The FieldSpec 4 Hi-Res NG, like all ASD spectroradiometers, incorporates superior spectral resolution, fast scanning gratings and graded index InGaAs photodiode SWIR detectors to provide the smallest spectral sampling interval in a field portable device with 1,875 measured wavelengths over the full 350 nm to 2,500 nm spectral range, ensuring detection of even the most subtle spectral features.

For results you can trust, and when accuracy really matters, the combination of high spectral resolution and small spectral sampling interval provides superior performance. This is in contrast to all array-based designs that sample the spectrum at relatively coarse intervals.

As you can see in the accompanying plot, the spectrum collected using the FieldSpec 4 Hi-Res NG (labeled “ASD”) has more detail and more smoothly defined spectral features while the coarser sampling interval of the all-array system (labeled “AAS”) results in more poorly defined features.

The number of detectors must be increased and the width of the detectors must be reduced to increase spectral sampling in an array-based spectrometer — this reduction in detector size worsens noise performance (top row of the second graphic). This trade-off between spectral sampling and noise limits the spectral detail that can be provided by an array-based spectrometer design.
In ASD’s SWIR fast scanner design, spectral sampling is maximized by measuring the detector at frequent intervals such that it acts as a much larger set of overlapping virtual detectors; there is no reduction in noise performance using this approach (bottom row of the second graphic). The FieldSpec 4’s fast scanner design eliminates the compromise between spectral sampling to provide spectra with the highest level of detail available in a field portable spectrometer.

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