Comparison of three grain size measuring methods applied to coarse-grained gravel deposits

The size of grains in gravel and conglomerate deposits is most easily measured on photos taken from related outcrops. However, the occlusion by sedimentary matrix or other grains, possible distortions photos, could introduce a bias such datasets. Here, we explore uncertainties associated with datasets where lengths were photos. To this end, analysed coarse-grained (>2 mm) fluvial material pit (Bern, Switzerland). We compared grain data collected digital results same was calliper mechanically sieved. Our analyses reveal that percentile values as D16, D50 D84 grains' longest visible axes best correlate to corresponding through sieving. also find are c. 17 % smaller than intermediate b-axes calliper. therefore suggest measure correct factor +17 for target percentiles.