ASTM D5923-18

Standard Guide for Selection of Kriging Methods in Geostatistical Site Investigations

SIGNIFICANCE AND USE
4.1 This guide is intended to encourage consistency and thoroughness in the application of kriging methods to environmental, geotechnical, and hydrogeological site investigations.  
4.2 This guide may be used to assist those performing a kriging study or as an explanation of procedures for qualified nonparticipants that may be reviewing or auditing the study.  
4.3 This guide encourages the use of site-specific information for the selection of an appropriate kriging method; however, the quality of data, the sampling density, and site coverage cannot be improved or compensated by any choice of kriging method.  
4.4 This guide describes conditions for which kriging or particular kriging methods are recommended. However, these methods are not necessarily inappropriate if the stated conditions are not encountered.  
4.5 This guide should be used in conjunction with Guides D5549, D5922, and D5924.
SCOPE
1.1 This guide covers recommendations for selecting appropriate kriging methods based on study objectives, exploratory data analysis, and analysis of spatial variation.  
1.2 This guide considers commonly used forms of kriging, including ordinary kriging, simple kriging, lognormal kriging, universal kriging, and indicator kriging. Multivariate, space-time, and other less-frequently used kriging methods are not discussed; however, this is not intended to reflect any judgement as to the validity of these methods.  
1.3 This guide describes conditions for which kriging methods are not appropriate and for which geostatistical simulations approaches should be used.  
1.4 This guide does not discuss non-geostatistical alternatives to kriging, such as splines or inverse-distance techniques.  
1.5 This guide does not discuss the basic principles of kriging. Introductions to geostatistics and kriging may be found in numerous texts including Refs (1-3).2 A review of kriging methods is given in Ref. (4).  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.7 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project's many unique aspects. The word “Standard” in the title of this document means only that the document has been approved through the ASTM consensus process.  
1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 14-Dec-2018
• ICS: 07.060 - Geology. Meteorology. Hydrology
• Technical Committee: D18 - Soil and Rock
• Drafting Committee: D18.01 - Surface and Subsurface Investigation

Relations

• Replaces: ASTM D5923-96(2010) - Standard Guide for Selection of Kriging Methods in Geostatistical Site Investigations
• Effective Date: 15-Dec-2018
• Refers: ASTM D5549-19 - Standard Guide for Contents of Geostatistical Site Investigation Report
• Effective Date: 01-May-2019
• Refers: ASTM D5922-18 - Standard Guide for Analysis, Interpretation, and Modeling of Spatial Variation in Geostatistical Site Investigations
• Effective Date: 15-Dec-2018
• Refers: ASTM D5924-18 - Standard Guide for Selection of Simulation Approaches in Geostatistical Site Investigations
• Effective Date: 15-Jul-2018
• Refers: ASTM D653-14 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Aug-2014
• Refers: ASTM D653-11 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Sep-2011
• Refers: ASTM D5922-96(2010) - Standard Guide for Analysis of Spatial Variation in Geostatistical Site Investigations
• Effective Date: 01-May-2010
• Refers: ASTM D5924-96(2010) - Standard Guide for Selection of Simulation Approaches in Geostatistical Site Investigations
• Effective Date: 01-May-2010
• Refers: ASTM D653-09 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Jan-2009
• Refers: ASTM D653-08a - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Dec-2008
• Refers: ASTM D653-08 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Nov-2008
• Refers: ASTM D653-07f - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 15-Dec-2007
• Refers: ASTM D653-07e - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Nov-2007
• Refers: ASTM D653-07d - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Aug-2007
• Refers: ASTM D653-07c - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Jul-2007

Overview

ASTM D5923-18: Standard Guide for Selection of Kriging Methods in Geostatistical Site Investigations is a widely recognized guide developed by ASTM International. The standard provides a framework for the selection of appropriate kriging methods-geostatistical estimation techniques-specifically for environmental, geotechnical, and hydrogeological site investigations. By encouraging consistency and thoroughness, ASTM D5923-18 ensures that practitioners apply kriging methods in a manner suited to their project objectives and site-specific conditions.

The guide is intended to support both practitioners conducting kriging studies and reviewers or auditors evaluating the work. It identifies various kriging approaches, outlines the circumstances for their use, and addresses scenarios where simulation or alternative methods might be more suitable. The standard should be used alongside related ASTM guides and incorporates internationally recognized principles of standardization.

Key Topics

ASTM D5923-18 covers several essential topics in geostatistical site investigations, focusing on:

• Selection of Kriging Methods: Provides recommendations based on study objectives, exploratory data analysis, and spatial variation analysis.
• Kriging Methods Considered: Includes ordinary kriging, simple kriging, lognormal kriging, universal kriging, and indicator kriging.
• Guidance on Data Quality: Emphasizes that choice of kriging method cannot compensate for poor data quality, low sampling density, or insufficient site coverage.
• Method Appropriateness: Details when kriging is recommended and highlights conditions where simulation methods may be preferable.
• Terminology: Defines key geostatistical terms such as block kriging, kriging variance, nugget effect, and variogram.
• Limitations: Excludes non-geostatistical alternatives and advanced forms like multivariate or space-time kriging.

Applications

The practical value of ASTM D5923-18 lies in its application to a wide range of site investigations where spatial data is analyzed and interpreted. Key uses include:

• Environmental Assessments: Assists in the spatial estimation of soil, groundwater, or contaminant concentrations, supporting risk evaluation and remediation planning.
• Geotechnical Investigations: Guides the estimation of physical properties of soils or rocks, contributing to better foundation and infrastructure design.
• Hydrogeological Studies: Supports estimation and mapping of properties such as hydraulic conductivity or transmissivity, essential for groundwater modeling.

Kriging methods selected according to this standard help produce spatial maps that offer reliable, least-squares estimates of unsampled locations or quantify spatial uncertainty, which is critical for robust decision-making in engineering, environmental, and regulatory contexts.

Related Standards

ASTM D5923-18 references and should be used in conjunction with several related ASTM guides:

• ASTM D653: Terminology Relating to Soil, Rock, and Contained Fluids.
• ASTM D5549: Guide for the Contents of Geostatistical Site Investigation Report.
• ASTM D5922: Guide for Analysis, Interpretation, and Modeling of Spatial Variation in Geostatistical Site Investigations.
• ASTM D5924: Guide for Selection of Simulation Approaches in Geostatistical Site Investigations.

By leveraging these standards alongside ASTM D5923-18, practitioners can ensure a comprehensive and methodical approach to geostatistical site investigations, leading to consistent, high-quality outcomes in environmental, geotechnical, and hydrogeological fields.

Keywords: ASTM D5923, kriging methods, geostatistics, environmental site investigation, geotechnical investigation, hydrogeology, spatial estimation, variogram, kriging variance.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D5923 − 18
Standard Guide for
Selection of Kriging Methods in Geostatistical Site
Investigations
This standard is issued under the fixed designation D5923; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Geostatistics is a framework for data analysis, estimation, and simulation in media whose
measurable attributes show erratic spatial variability yet also possess a degree of spatial continuity
imparted by the natural and anthropogenic processes operating therein. The soil, rock, and contained
fluids encountered in environmental or geotechnical site investigations present such features, and their
sampled attributes are therefore amenable to geostatistical treatment. Kriging methods are geostatis-
tical techniques for spatial estimation belonging to the class of least-squares estimators. This guide
reviews criteria for selecting a kriging method, offering direction based on a consensus of views
without recommending a standard practice to follow in all cases.
1. Scope priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.1 This guide covers recommendations for selecting appro-
1.7 This guide offers an organized collection of information
priate kriging methods based on study objectives, exploratory
or a series of options and does not recommend a specific
data analysis, and analysis of spatial variation.
course of action. This document cannot replace education or
1.2 This guide considers commonly used forms of kriging,
experienceandshouldbeusedinconjunctionwithprofessional
including ordinary kriging, simple kriging, lognormal kriging,
judgment. Not all aspects of this guide may be applicable in all
universal kriging, and indicator kriging. Multivariate, space-
circumstances. This ASTM standard is not intended to repre-
time, and other less-frequently used kriging methods are not
sent or replace the standard of care by which the adequacy of
discussed; however, this is not intended to reflect any judge-
a given professional service must be judged, nor should this
ment as to the validity of these methods.
document be applied without consideration of a project’s many
1.3 This guide describes conditions for which kriging meth-
unique aspects. The word “Standard” in the title of this
odsarenotappropriateandforwhichgeostatisticalsimulations
document means only that the document has been approved
approaches should be used.
through the ASTM consensus process.
1.4 This guide does not discuss non-geostatistical alterna-
1.8 This international standard was developed in accor-
tives to kriging, such as splines or inverse-distance techniques.
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
1.5 This guide does not discuss the basic principles of
kriging. Introductions to geostatistics and kriging may be Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
found in numerous texts including Refs (1-3). A review of
kriging methods is given in Ref. (4). Barriers to Trade (TBT) Committee.
1.6 This standard does not purport to address all of the
2. Referenced Documents
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
2.1 ASTM Standards:
D653 Terminology Relating to Soil, Rock, and Contained
Fluids
This guide is under the jurisdiction ofASTM Committee D18 on Soil and Rock
and is the direct responsibility of Subcommittee D18.01 on Surface and Subsurface
Characterization.
Current edition approved Dec. 15, 2018. Published December 2018. Originally
approved in 1996. Last previous edition approved in 2010 as D5923 – 96(2010). For referenced ASTM standards, visit the ASTM website, www.astm.org, or
DOI: 10.1520/D5923-18. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
The boldface numbers in parentheses refer to a list of references at the end of Standards volume information, refer to the standard’s Document Summary page on
the text. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5923 − 18
D5549 Guide for The Contents of Geostatistical Site Inves- 3.2.13 point, n—in geostatistics, the location in the field at
tigation Report (Withdrawn 2002) which a regionalized variable is defined. It also commonly
D5922 Guide for Analysis of Spatial Variation in Geostatis- refers to the support of sample-scale variables.
tical Site Investigations
3.2.14 point kriging, n—a form of kriging in which the
D5924 Guide for Selection of Simulation Approaches in
variable to be estimated has the same support as the sample
Geostatistical Site Investigations
data.
3.2.15 regionalized variable, n—a measured quantity or a
3. Terminology
numerical attribute characterizing a spatially variable phenom-
3.1 Definitions:
enon at a location in the field.
3.1.1 For definitions of common technical terms used in this
3.2.16 search neighborhood, n—the region within which
standard, refer to Terminology D653.
samples are considered for inclusion in the kriging estimation
3.2 Definitions of Terms Specific to This Standard:
process.
3.2.1 additivity, n—a mathematical property of a regional-
3.2.17 simple kriging, n—a form of kriging for which the
izedvariablestatingthatitcanbecombinedlinearlyinorderto
meanoftheestimatedvariableisaknownconstantandthesum
define a similar variable on a larger support.
of sample weights is unconstrained.
3.2.2 block kriging, n—a form of kriging in which the
3.2.18 simulation, n—in geostatistics, a Monte-Carlo proce-
variable to be estimated has a rectangular or possibly irregular
dure for generating realizations of fields based on the random
one-, two-, or three-dimensional support.
function model chosen to represent a regionalized variable. In
3.2.3 drift, n—in geostatistics, a systematic spatial variation
addition to honoring a random function model, the realizations
of the local mean of a variable, usually expressed as a
may also be constrained to honor data values observed at
polynomial function of location coordinates.
sampled locations.
3.2.4 estimation, n—in geostatistics, a procedure by which
3.2.19 smoothing effect, n—in geostatistics, the reduction in
the value of a variable at an unsampled location is predicted
spatial variance of estimated values compared to true values.
using a weighted average of sample values from the neighbor-
3.2.20 spatial average, n—a quantity obtained by averaging
hood of that location.
a regionalized variable over a finite region of space.
3.2.5 field, n—in geostatistics, the region of one-, two- or
3.2.21 support, n—in geostatistics, the spatial averaging
three-dimensional space within which a regionalized variable
region over which a regionalized variable is defined, often
is defined.
approximated by a point for sample-scale variables.
3.2.6 indicator kriging, n—a form of kriging in which all
3.2.22 universal kriging, n—a form of kriging in which
data are indicator variables.
additional weighting constraints are introduced in order to
3.2.7 indicator variable, n—a regionalized variable that can
account for a drift in the estimated variable.
have only two possible values, 0 or 1.
3.2.23 variogram, n—a measure of spatial variation defined
3.2.8 kriging, n—an estimation method where sample
asonehalfthevarianceofthedifferencebetweentwovariables
weights are obtained using a linear least-squares optimization
and expressed as a function of the lag; it is also sometimes
procedure based on a mathematical model of spatial variability
referred to as the semi-variogram.
and where the unknown variable and the available sample
values may have a point or block support.
4. Significance and Use
3.2.9 kriging variance, n—theexpectedvalueofthesquared
4.1 This guide is intended to encourage consistency and
difference between the true value of an unknown variable and
thoroughness in the application of kriging methods to
its kriging estimate, sometimes used as a measure of kriging
environmental, geotechnical, and hydrogeological site investi-
precision.
gations.
3.2.10 lognormal kriging, n—thekrigingoflog-transformed
4.2 This guide may be used to assist those performing a
variables followed by a back-transformation procedure based
kriging study or as an explanation of procedures for qualified
on a lognormal distribution model.
nonparticipants that may be reviewing or auditing the study.
3.2.11 nugget effect, n—the component of spatial variance
unresolved by the sample spacing, including the variance due 4.3 This guide encourages the use of site-specific informa-
to measurement error. tion for the selection of an appropriate kriging method;
however, the quality of data, the sampling density, and site
3.2.12 ordinary kriging, n—a form of kriging for which the
coverage cannot be impro
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D5923 − 96 (Reapproved 2010) D5923 − 18
Standard Guide for
Selection of Kriging Methods in Geostatistical Site
Investigations
This standard is issued under the fixed designation D5923; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Geostatistics is a framework for data analysis, estimation, and simulation in media whose
measurable attributes show erratic spatial variability yet also possess a degree of spatial continuity
imparted by the natural and anthropogenic processes operating therein. The soil, rock, and contained
fluids encountered in environmental or geotechnical site investigations present such features, and their
sampled attributes are therefore amenable to geostatistical treatment. Kriging methods are geostatis-
tical techniques for spatial estimation belonging to the class of least-squares estimators. This guide
reviews criteria for selecting a kriging method, offering direction based on a consensus of views
without recommending a standard practice to follow in all cases.
1. Scope
1.1 This guide covers recommendations for selecting appropriate kriging methods based on study objectives, exploratory data
analysis, and analysis of spatial variation.
1.2 This guide considers commonly used forms of kriging, including ordinary kriging, simple kriging, lognormal kriging,
universal kriging, and indicator kriging. Multivariate, space-time, and other less-frequently used kriging methods are not discussed;
however, this is not intended to reflect any judgement as to the validity of these methods.
1.3 This guide describes conditions for which kriging methods are not appropriate and for which geostatistical simulations
approaches should be used.
1.4 This guide does not discuss non-geostatistical alternatives to kriging, such as splines or inverse-distance techniques.
1.5 This guide does not discuss the basic principles of kriging. Introductions to geostatistics and kriging may be found in
numerous texts including Refs (1-3). A review of kriging methods is given in Ref. (4).
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.7 This guide offers an organized collection of information or a series of options and does not recommend a specific course
of action. This document cannot replace education or experience and should be used in conjunction with professional judgment.
Not all aspects of this guide may be applicable in all circumstances. This ASTM standard is not intended to represent or replace
the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied
without consideration of a project’s many unique aspects. The word “Standard” in the title of this document means only that the
document has been approved through the ASTM consensus process.
1.8 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
This guide is under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.01 on Surface and Subsurface
Characterization.
Current edition approved May 1, 2010Dec. 15, 2018. Published September 2010December 2018. Originally approved in 1996. Last previous edition approved in 20042010
as D5923 – 96 (2004). 96(2010). DOI: 10.1520/D5923-96R10.10.1520/D5923-18.
The boldface numbers in parentheses refer to a list of references at the end of the text.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5923 − 18
2. Referenced Documents
2.1 ASTM Standards:
D653 Terminology Relating to Soil, Rock, and Contained Fluids
D5549 Guide for The Contents of Geostatistical Site Investigation Report (Withdrawn 2002)
D5922 Guide for Analysis, Interpretation, and Modeling of Spatial Variation in Geostatistical Site Investigations
D5924 Guide for Selection of Simulation Approaches in Geostatistical Site Investigations
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 additivity, n—a mathematical property of a regionalized variable stating that it can be combined linearly in order to define
a similar variable on a larger support.
3.1.2 block kriging, n—a form of kriging in which the variable to be estimated has a rectangular or possibly irregular one-, two-,
or three-dimensional support.
3.1.3 drift, n—in geostatistics, a systematic spatial variation of the local mean of a variable, usually expressed as a polynomial
function of location coordinates.
3.1.4 estimation, n—a procedure by which the value of a variable at an unsampled location is predicted using a weighted average
of sample values from the neighborhood of that location.
3.1.5 field, n—in geostatistics, the region of one-, two- or three-dimensional space within which a regionalized variable is
defined.
3.1.6 indicator kriging, n—a form of kriging in which all data are indicator variables.
3.1.7 indicator variable, n—a regionalized variable that can have only two possible values, 0 or 1.
3.1.8 kriging, n—an estimation method where sample weights are obtained using a linear least-squares optimization procedure
based on a mathematical model of spatial variability and where the unknown variable and the available sample values may have
a point or block support.
3.1.9 kriging variance, n—the expected value of the squared difference between the true value of an unknown variable and its
kriging estimate, sometimes used as a measure of kriging precision.
3.1.10 lognormal kriging, n—the kriging of log-transformed variables followed by a back-transformation procedure based on
a lognormal distribution model.
3.1.11 nugget effect, n—the component of spatial variance unresolved by the sample spacing, including the variance due to
measurement error.
3.1.12 ordinary kriging, n—a form of kriging for which the mean of the estimated variable is an unknown constant and the
sample weights sum to one.
3.1.13 point, n—in geostatistics, the location in the field at which a regionalized variable is defined. It also commonly refers
to the support of sample-scale variables.
3.1.14 point kriging, n—a form of kriging in which the variable to be estimated has the same support as the sample data.
3.1.15 regionalized variable, n—a measured quantity or a numerical attribute characterizing a spatially variable phenomenon
at a location in the field.
3.1.16 search neighborhood, n—the region within which samples are considered for inclusion in the kriging estimation process.
3.1.17 simple kriging, n—a form of kriging for which the mean of the estimated variable is a known constant and the sum of
sample weights is unconstrained.
3.1.18 simulation, n—in geostatistics, a Monte-Carlo procedure for generating realizations of fields based on the random
function model chosen to represent a regionalized variable. In addition to honoring a random function model, the realizations may
also be constrained to honor data values observed at sampled locations.
3.1.19 smoothing effect, n—in geostatistics, the reduction in spatial variance of estimated values compared to true values.
3.1.20 spatial average, n—a quantity obtained by averaging a regionalized variable over a finite region of space.
3.1.21 support, n—in geostatistics, the spatial averaging region over which a regionalized variable is defined, often
approximated by a point for sample-scale variables.
3.1.22 universal kriging, n—a form of kriging in which additional weighting constraints are introduced in order to account for
a drift in the estimated variable.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
D5923 − 18
3.1.23 variogram, n—a measure of spatial variation defined as one half the variance of the difference between two variables and
expressed as a function of the lag; it is also sometimes referred to as the semi-variogram.
3.1 For definitions of other terms used in this guide, refer to Terminology D653 and Guides D5549, D5922, and D5924. A
complete glossary of geostatistical terminology is given in Ref (5).Definitions:
3.1.1 For definitions of common technical terms used in this standard, refer to Terminology D653.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 additivity, n—a mathematical property of a regionalized variable stating that it can be combined linearly in order to define
a similar variable on a larger support.
3.2.2 block kriging, n—a form of kriging in which the variable to be estimated has a rectangular or possibly irregular one-, two-,
or three-dimensional support.
3.2.3 drift, n—in geostatistics, a systematic spatial variation of the local mean of a variable, usually expressed as a polynomial
function of location coordinates.
3.2.4 estimation, n—in geostatistics, a procedure by which the value of a variable at an unsampled location is predicted using
a weighted average of sample values from the neighborhood of that location.
3.2.5 field, n—in geostatistics, the region of one-, two- or three-dimensional space within which a regionalized variable is
defined.
3.2.6 indicator kriging, n—a form of kriging in which all data are indicator variables.
3.2.7 indicator variable, n—a regionalized variable that can have only two possible values, 0 or 1.
3.2.8 kriging, n—an estimation method where sample weights are obtained using a linear least-squares optimization procedure
based on a mathematical model of spatial variability and where the unknown variable and the available sample values may have
a point or block support.
3.2.9 kriging variance, n—the expected value of the squared difference between the true value of an unknown variable and its
kriging estimate, sometimes used as a measure of kriging precision.
3.2.10 lognormal kriging, n—the kriging of log-transformed variables followed by a back-transformation procedure based on
a lognormal distribution model.
3.2.11 nugget effect, n—the component of spatial variance unresolved by the sample spacing, including the variance due to
measurement error.
3.2.12 ordinary kriging, n—a form of kriging for which the mean of the estimated variable is an unknown constant and the
sample weights sum to one.
3.2.13 point, n—in geostatistics, the location in the field at which a regionalized variable is defined. It also commonly refers
to the support of sample-scale variables.
3.2.14 point kriging, n—a form of kriging in which the variable to be es
...