A sampling strategy for quantitative soil survey includes two different samplings : (i) a reconnaissance sampling to characterize the variogram required to optimize the sampling scheme for (ii) the actual survey. For the actual survey a sampling
spacing of 2 km in a square grid was found to result in an acceptable maximum kriging estimation error of 5,76 %. The proposed sampling strategy would require 408 observations in total. This is 71 % less than the sampling during the National Soil Survey.
Canada ; Cold area ; Comparative study ; Core sampling ; Freezing ; Gaspé ; Quebec ; Research technique ; River bed ; Sampling ; Statistical bias
The aims of this paper are to quantify the relative biases of the freeze-core and bulk sampling techniques against more accurate composite samples and to examine whether systematic losses of fines can be predicted. At 6 riffles the spawning
substrate was sampled under approximately 50 cm of water with a bulk sample and 3 adjacent freeze-cores. For each riffle, data from the 2 samples were combined using the method of Fripp and Diplas (1993) and the resultant composite sample was compared
with the original freeze-core and bulk samples to assess the relative precision and biases of the 2 techniques.
An examination of the efficiency of a simple runoff plot sample splitter
The study investigated the effect of flow rate, sediment concentration and sediment grain size on the efficiency of a simple runoff plot sample splitter. Results of the study showed that surface tension affects sampler efficiency at low flow rates
. The sample splitter achieves maximum efficiency once a critical rate of 0,15 1.s-1 has been exceeded.
The objective of the study is to review the literature on sampling methods for estimating landscape metrics. Sampling-based approaches for the estimation of landscape metrics appear promising.
Establishing qualitative geographic sample size in the presence of spatial autocorrelation
Analysis of variance ; Applied geography ; Quantitative geography ; Sampling ; Spatial analysis ; Spatial autocorrelation ; Spatial distribution
This article analyses the qualitative sample size determination for many purposeful sampling designs. It demonstrates that spatial autocorrelation can have a noticeable effect on sampling, whether it is quantitative or qualitative in nature
. The results show firstly, that many sample sizes reported in the literature to dateappear to be inadequate to ensure that saturation was achieved. Secondly, that determining the level of positive spatial autocorrelation for a selection variable allows
aggregate areal units to be targeted that will better suit purposeful sampling designs. And thirdly, that because because snowball sampling tends to be guided by positive spatial autocorrelation, communities should be targeted that display very high levels
The objective of this investigation was to determine optimal sampling scheme and distances, which allow to calculate the most informative semi-variogram for all variables of interest by only one sampling event. Nested sampling and nested analysis
A field comparison of three pressure-difference bedload samplers
In this study, sample weights collected by 3 types of pressure-difference samplers are compared to determine whether differences are statistically significant. The implication of the results is that measured transport rates will vary depending
on the sampler used and, therefore, they are not directly comparable without some mode of calibration. To place this finding in a larger context, sediment rating curves, determined from weights of samples and measurements of flow, were integrated over available
A minimum sample size required from Schmidt hammer measurements
Central Europe ; Europe ; Geomorphology ; Instrumentation ; Lithology ; Methodology ; Sampling ; Statistical analysis ; Sudety ; Weathering
The AA. show a simple statistical method, based on the two-sample Student’s t-test, to objectively estimate the minimum number of rebound measurements. They present the results as (1) the ‘mean’ and ‘median’ solutions, each providing a single
estimate value, and (2) the empirical probability distribution of such estimates based on many field samples. Schmidt hammer data for 14 lithologies, 13–81 samples for each, with each sample consisting of 40 individual readings, have been evaluated
, assuming different significance levels. Principal recommendations are given : recommended minimum sample size and required number of readings at a site.
This paper presents two approaches to using a data logger to interface between a flow recorder and a sampler, and provides a framework for the collection of high quality data from the field. Two hydrological systems were monitored; both
Accuracy of two sampling methods used to estimate sediment concentrations in runoff from soil-loss plots
This paper presents the results of a study into the accuracy of a sampling procedure described by Wiltshire (1948) which involves the sampling of suspended sediment in both the field and the laboratory.
Bulk sampling of coarse clastic sediments for particle-size analysis
A guide is provided to the minimum sample masses required to obtain reproducible measures of the particle-size distributions of coarse sediments. This is based on studies of the actual particle-size distributions of a range of clastic deposits
. Procedures are given to enable representative bulk samples of tills, fluvial gravels and beach gravels to be taken.
An examination of the efficiency of a simple runoff plot sample splitter
The study investigated the effect of flow rate, sediment concentration and sediment grain size on the efficiency of a simple runoff plot sample splitter.
A hand-held core sampler for plastic benthic sediments
Australia ; Core sampling ; Lacustrine sediment ; Lake ; Methodology ; Sedimentology ; Victoria
The sampler is based on the previous design of Miller and Bingham (1987) but incorporates two important modifications. The first prevents detachment and possible loss of the piston's sealing plug. The second is a support frame which enables
the corer to sample plastic sediments whithout compressing and distorting the core. The device was used successfully to take cores from the bottom of Lake Wellington, Gippsland, Victoria.
Canada ; Glacier ; Glacier mass balance ; Kyrgyzstan ; Methodology ; Model ; Northwest Territories ; Principal components analysis ; Sampling ; Spatial statistics
The A. aims to determine the effective sample size of 2 glaciers by analysis of the spatial correlation between point mass balance measurements. Correlograms from multiple time series of point mass balance, measured on White Glacier (Axel Heiberg
Island, Canada) and Abramov Glacier (Alai Range, Kirgizia), show that the correlation decreases with the difference in elevation between the points. A principal component analysis confirms that the effective sample size is very small.
Experiments carried out under temperatures and relative humidities that approximate ambient conditions show that the rate of hydration of obsidian is a function of the relative humidity. Surface samples of obsidian exposed to solar heating should
hydrate more rapidly than samples buried in the ground. However, the effect of the lower mean relative humidity experiences by surface samples tends to compensate for the elevated temperature, which may explain why obsidian hydration ages of surface
samples usually approximate those derived from buried samples.
Benefits of design modifications to the Birthbeck bedload sampler illustrated by flash-floods in an ephemeral gravel-bed channel
Arid area ; Carrying capacity ; Flood ; Israel ; Research technique ; Sampling ; Sediment load ; Stream
The benefits of 3 simple modifications to the design of a Birkbeck bedload slot-sampling system that has been continuously operating in Nabal Eshtemoa, Israel, since the early 1990s are demonstrated : the deployment of a removable slot cover whivh
delays the accumulation of sediment; inclusion of a slot the size of which is adjustable; and a sampler side-wall door that allows stratification and textural changes within the accumulated bedload to be identified.