DOI: 10.5066/p13tue9u
title: Spectral reflectance data of rock and soil in Prince William Sound, Alaska

description: An ASD FieldSpec 4 Hi-Res NG Spectroradiometer was used to collect the reflectance properties of soil and rock in Prince William Sound (Figure 1). Reflectance is a property of the material being observed, being the ratio of the amount of light leaving a target to the amount of light striking the target. Reflectance is a unitless value from 0 to 1, where a value of 0 indicates that the material absorbs all energy and 1 indicates total reflectance. The ASD FieldSpec 4 Hi-Res NG is a point spectrometer that has a spectral range of 350 to 2500 nm, covering the visible and near-infrared (VNIR) and short-wave infrared (SWIR) portions of the electromagnetic spectrum. The spectral resolution is 3 nm at 700 nm and 6 nm at 1400 and 2100 nm, and the spectral sampling (bandwidth) is 1.4 nm at 700 nm and 1.1 nm at 1400 and 2100nm. The instrument collects 2151 channels of spectral data (Malvern Panalytical, 2023).

This data release is an extension of Schaefer and Ellison (2023), which contains rock and soil reflectance properties of the Anchorage area and western Prince William Sound. To maintain consistency, the attached .txt files are formatted in the same way as Schaefer and Ellison (2023). Differences between that data release and this one include: (1) No reflectance data was collected directly in the field. Instead, rock and soil samples were collected in the field in the summer and fall of 2023 and later measured in the laboratory. (2) No cut rock surfaces were measured for this data release. Only reflectance data of the external portions of the rock samples ("uncut" surface) are provided herein. All measurements were made using a contact probe with a 10 mm spot size that uses artificial light provided by a halogen bulb. Ten measurements were collected for each entry, during which the probe was moved to capture different surfaces of the sample to assure all representative features were measured. During the measurement period, the ASD spectrometer settings (integration times and gain factors) were re-optimized every 10 minutes using a National Institute of Standards and Technology traceable Labsphere Spectralon® 99% reflective reference panel (Spectralon panel). The ten spectra measurements were then averaged, after which a splice correction was applied using the ASD ViewSpec Pro software that corrects steps in the data due to inherent variations in detector temperature sensitivity (Milton and others, 2009). Measurements provided are relative reflectance, not absolute reflectance; conversion of relative to absolute reflectance via compensation for the absorption properties of the reference panel is described in Clark and others (2022). Reflectance data of the Spectralon panel can be found in Kokaly and others (2017).
 
The files provided in this data release are as follows:
 
Figure 1 (“Figure1.jpg”, “Figure1.pdf”) is a map showing locations where samples were collected from the field and later measured in the laboratory, and location of the Prince William Sound study area in Alaska.  
 
“Metadata.xml” is the metadata for the data release.
 
“PWS_2023_DataDictionary.txt” is a tab delimited text file that contains descriptions of the names and definitions for each attribute.
 
“PWS_2023_SampleLocationsandDescriptions.txt” is a tab delimited text file that provides details of the samples and sample locations.
 
“PWS_2023_SpectraData.txt” is a tab delimited text file that contains the averaged and splice corrected spectral reflectance data (relative, unitless) for each of the samples listed in “PWS_2023_SampleLocationsandDescriptions.txt”
 
Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
 
References Cited
Clark, R.N., Swayze, G.A., Livo, K.E., Kokaly, R.F., King, T.V., Dalton, J.B., Vance, J.S., Rockwell, B.W., Hoefen, T. and McDougal, R.R., 2002, March. Surface reflectance calibration of terrestrial imaging spectroscopy data: a tutorial using AVIRIS. In: Proceedings of the 10th Airborne Earth Science Workshop (Vol. 2). Pasadena, CA, USA: Jet Propulsion Laboratory.
 
Kokaly, R.F., Clark, R.N., Swayze, G.A., Livo, K.E., Hoefen, T.M., Pearson, N.C., Wise, R.A., Benzel, W.M., Lowers, H.A., Driscoll, R.L., and Klein, A.J., 2017, USGS Spectral Library Version 7: U.S. Geological Survey Data Series 1035, 61 p., https://doi.org/10.3133/ds1035
 
Malvern Panalytical, 2023, ASD FieldSpec 4 Hi-Res NG Spectroradiometer, accessed 27 January 2023 at https://www.malvernpanalytical.com/en/support/product-support/asd-range/fieldspec-range/fieldspec-4-hi-res-ng-spectroradiometer
 
Milton, E. J., Schaepman, M. E., Anderson, K., Kneubühler, M., & Fox, N. (2009). Progress in field spectroscopy. Remote Sensing of Environment, 113, S92-S109. https://doi.org/10.1016/j.rse.2007.08.001

Schaefer, L.N., and Ellison, S.M., 2023, Spectral reflectance data of rock and soil in southcentral Alaska: U.S. Geological Survey data release, https://doi.org/10.5066/P96VBU9U
 
Acknowledgments 
The authors wish to thank G. Belair, S. Lahusen, and N. Avdievitch for assistance in collecting field samples.