Comment: Photographic Techniques for Characterizing Streambed Particle Sizes

Graham, David J.; Rice, Stephen P.; Reid, Ian

doi:10.1577/t04-146.1

Cited by 10 publications

(9 citation statements)

References 17 publications

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“…Grain size was measured by hand in each ChemCam target using the National Institute of Health software package ImageJ [Schneider et al, 2012], which is a program for image processing and analysis. Particle size analyses of RMI images were performed for each target using a photographic grid-by-number sampling approach [Graham et al, 2005]. This conventional method would set the grid spacing at twice the maximum grain diameter [Graham et al, 2005].…”

Section: Grain Size Determination From Rmimentioning

confidence: 99%

“…However, this aspect of the grid-by-number sampling approach is not feasible for RMI images with a narrow depth of focus because the range of grain sizes in a given RMI image could encompass 1-2 orders of magnitude. This greatly reduces the number of smaller diameter grains measured when the grid spacing is set at twice the maximum grain diameter [Graham et al, 2005;Karunatillake et al, 2014aKarunatillake et al, , 2014b and thereby defeats the purpose of the measuring campaign, which was to assess the average grain size in RMI images.…”

Section: Grain Size Determination From Rmimentioning

confidence: 99%

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Geochemistry of the Bagnold dune field as observed by ChemCam and comparison with other aeolian deposits at Gale Crater

et al. 2017

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The Curiosity rover conducted the first field investigation of an active extraterrestrial dune. This study of the Bagnold dunes focuses on the ChemCam chemical results and also presents findings on the grain size distributions based on the ChemCam Remote Micro‐Imager and Mars Hand Lens Imager images. These active dunes are composed of grains that are mostly <250 μm. Their composition is overall similar to that of the aeolian deposits analyzed all along the traverse (“Aeolis Palus soils”). Nevertheless, the dunes contain less volatiles (Cl, H, and S) than the Aeolis Palus soils, which appear to be due to a lower content of volatile‐rich fine‐grained particles (<100 μm) or a lower content of volatile‐rich amorphous component, possibly as a result of (1) a lower level of chemical alteration, (2) the removal of an alteration rind at the surface of the grains during transport, (3) a lower degree of interaction with volcanic gases/aerosols, or (4) physical sorting that removed the smallest and most altered grains. Analyses of the >150 μm grain‐size dump piles have shown that coarser grains (150–250 μm) are enriched in the mafic elements Fe and Mn, suggesting a larger content in olivine compared to smaller grains (<150 μm) of the Bagnold dunes. Moreover, the chemistry of soils analyzed in the vicinity of the dunes indicates that they are similar to the dune material. All these observations suggest that the olivine content determined by X‐ray diffraction of the <150 μm grain‐size sample should be considered as a lower limit for the Bagnold dunes.

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Section: Grain Size Determination From Rmimentioning

confidence: 99%

Section: Grain Size Determination From Rmimentioning

confidence: 99%

Geochemistry of the Bagnold dune field as observed by ChemCam and comparison with other aeolian deposits at Gale Crater

et al. 2017

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“…It is likely that these effects result from the sensitivity of the conversion to small variations in the coarsest part of the grain-size distribution. This effect was examined in detail by Graham et al (2005c).…”

Section: Field-based Assessmentmentioning

confidence: 99%

Conversions of Surface Grain-Size Samples Collected and Recorded Using Different Procedures

et al. 2012

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Abstract:Information about the grain-size distribution of the surface layer of sediment exposed on river beds is often critical in studies of fluvial hydraulics, geomorphology and ecology. A variety of sampling and analysis techniques are in common usage which produce grain-size distributions that are not directly comparable. This paper seeks to explore the appropriate conversions between different types of surface grain-size sampling methods. This is particularly timely in the light of increasingly widespread use of automatic and semiautomatic image-based measurement methods, the comparability of which with conventional measurement methods is relatively poorly constrained. For conversions between area-bynumber (paint-and-pick) and grid-by-number (pebble count) samples, the empirically-derived conversion factor (±2.2) was found to be greater than that predicted by the Kellerhals and Bray model (±2), but the errors associated with using the value predicted by the model were small (3.8% in mm). For conversions between areal samples recorded by count and weight, 2 the empirically-derived conversion factor was approximately ±2.9, but the use of the value predicted by the Kellerhals and Bray model (±3) resulted in only small errors (5.2% in mm).Similarly, for conversions between image-based grain-size distributions recorded in area-bynumber and grid-by number form, the emipirically-derived conversion factor was ±1.9, but the using the model value of ±2 resulted in only small errors (4.1% in mm). Although these results are specific to the datasets analysed, the variety of sedimentary conditions included gives us confidence that the results are representative.

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“…Fundamental measurement studies such as McHugh and Budy's (2005) continue to be needed. However, the above observations and the comments by Graham et al (2005) illustrate the importance of ensuring that we are indeed measuring the intended quantity, especially in the case of coarse bed substrates in salmonid habitat.…”

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confidence: 98%

“…The results for percent fines indicate a relatively good precision about their regression line and suggest that visually based estimates can be relied upon for management purposes, given an appropriate observer calibration. Nonetheless, comments made by Graham et al (2005) concerning the use of pebble counts for determining fines concentrations apply.…”

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confidence: 99%

Comment: A Comparison of Visual and Measurement‐Based Techniques for Quantifying Cobble Embeddedness and Fine‐Sediment Levels in Salmonid‐Bearing Streams

DeVries¹

2007

N American J Fish Manag

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Comment: Photographic Techniques for Characterizing Streambed Particle Sizes

Cited by 10 publications

References 17 publications

Geochemistry of the Bagnold dune field as observed by ChemCam and comparison with other aeolian deposits at Gale Crater

Geochemistry of the Bagnold dune field as observed by ChemCam and comparison with other aeolian deposits at Gale Crater

Conversions of Surface Grain-Size Samples Collected and Recorded Using Different Procedures

Comment: A Comparison of Visual and Measurement‐Based Techniques for Quantifying Cobble Embeddedness and Fine‐Sediment Levels in Salmonid‐Bearing Streams

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