Impact of Improved Calibration of a NEO HySpex VNIR-1600 Sensor on Remote Sensing of Water Depth

Abstract

This paper investigates at the example of bathymetry how much an application can profit from comprehensive characterizations required for an improved calibration of data from a state-of-the-art commercial hyperspectral sensor. A NEO HySpex VNIR-1600 sensor is used for this paper, and the improvements are based on measurements of sensor properties not covered by the manufacturer, in particular, detector nonlinearity and stray light. This additional knowledge about the instrument is used to implement corrections for nonlinearity, stray light, spectral smile distortion and nonuniform spectral bandwidth and to base the radiometric calibration on a SI-traceable radiance standard. Bathymetry is retrieved from a data take from the lake Starnberg using WASI-2D. The results using the original and improved calibration procedures are compared with ground reference data, with an emphasis on the effect of stray-light correction. For our instrument, stray-light biases the detector response from 416-500 nm up to 8% and from 700-760 nm up to 5%. Stray-light-induced errors affect bathymetry mainly in water deeper than Secchi depth, whereas in shallower water, the dominant error source is the calibration accuracy of the light source used for radiometric calibration. Stray-light correction reduced the systematic error of water depth by 19% from Secchi depth to three times Secchi depth, whereas the relative standard deviation remained stable at 5%.

Airborne Imaging Spectrometer HySpex

“…DLR Remote Sensing Technology Institute., 2016). Since an in depth treatment of the afore mentioned e orts can be found in Lenhard, Baumgartner, & Schwarzmaier (2015) and Lenhard, Baumgartner, Gege, et al (2015), the interested reader is referred to these publications for details. Section 2.2 is dedicated to the description of the navigation system used for absolute georeferencing of the acquired image data.…”

“…In order to correct detector non-linearity and stray light, several measurements were performed in cooperation with PTB within the framework of the EURAMET project. Lenhard, Baumgartner, Gege, et al (2015) elaborate on the associated methods and discuss the achievable improvements for the exemplary application of inland water depth retrieval.…”

The Calibration Home Base for Imaging Spectrometers

“…• On the improvement that can be achieved through thorough hyperspectral sensor calibration (Lenhard, Baumgartner, Gege, et al, 2015).…”

A “Skylight” Simulator for HWIL Simulation of Hyperspectral Remote Sensing

“…Although the precision reflectance model of buildings and canopies [8,9] and the mixing model of minerals (such as the Hapke model [10,11]) have been developed, and the precision model of a spectrometer can also be specifically built [12], it is still important to measure reflected radiance in a hardware-in-the-loop (HWIL) simulation when researching the influence of environment, such as heavy metal toxicity in plants, nonlinear mixing of minerals, or weathered minerals [13,14,15,16,17,18,19,20,21,22]. The traditional approaches include conducting flight campaigns over experimental sites [13,14,15] and experiments in labs [16,17,18,19,20,21,22].…”

“…The traditional approaches include conducting flight campaigns over experimental sites [13,14,15] and experiments in labs [16,17,18,19,20,21,22]. The flight campaign approach has several shortcomings such as the great expense, time consumption, the complexity and difficulty of making simultaneous in-situ measurements of atmospheric parameters and ground reflective characteristics.…”