Australian Soil and Land Survey Field Handbook third edition The National Committee ON Soil and Terrain
Australian Soil and Land Survey Field Handbook THIRD EDITION
Australian Soil and Land Survey Field Handbook THIRD EDITION
THE NATIONAL COMMITTEE ON SOIL AND TERRAIN
© CSIRO 2009 All rights reserved. Except under the conditions described in the Australian Copyright Act 1968 and subsequent amendments, no part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, duplicating or otherwise, without the prior permission of the copyright owner. Contact CSIRO PUBLISHING for all permission requests. National Library of Australia Cataloguing-in-Publication entry Australian soil and land survey field handbook. 3rd ed. Collingwood, Vic. : CSIRO Publishing, 2009. 9780643093959 (pbk.) Australian soil and land survey handbooks ; no. 1 Includes index. Bibliography. Landforms – Australia – Classification – Handbooks, manuals, etc. Soil surveys – Australia – Handbooks, manuals, etc. Land use surveys – Australia – Handbooks, manuals, etc. Vegetation classification – Australia – Handbooks, manuals, etc. 631.4794 First edition 1984; Second edition 1990 Published by CSIRO PUBLISHING 150 Oxford Street (PO Box 1139) Collingwood VIC 3066 Australia Telephone: Local call: Fax: Email: Web site:
+61 3 9662 7666 1300 788 000 (Australia only) +61 3 9662 7555
[email protected] www.publish.csiro.au
Front cover image (by Linda Gregory): soil landform elements overlaid on shaded elevation. Data sources: Hook R, McPherson A, Glover M, McKenzie NJ, Aldrick J (2002) Land and soil survey, Simmons Creek Catchment, Walbundrie, NSW; and AAM Geoscan (2001) Airborne laser scanning survey of the Simmons Creek Catchment area, 10 m digital elevation model. Set in 10/13 Adobe Palatino and Adobe Sabon Edited by Alexa Cloud Cover and text design by James Kelly Typeset by Desktop Concepts Pty Ltd, Melbourne Printed in China by 1010 Printing International Ltd CSIRO PUBLISHING publishes and distributes scientific, technical and health science books, magazines and journals from Australia to a worldwide audience and conducts these activities autonomously from the research activities of the Commonwealth Scientific and Industrial Research Organisation (CSIRO). The views expressed in this publication are those of the author(s) and do not necessarily represent those of, and should not be attributed to, the publisher or CSIRO.
CONTENTS
Preface to the first edition
xi
Preface to the second edition
xiii
Preface to the third edition
xiv
Acknowledgements
xvii
Purpose and use of handbook
J.G. Speight and R.F. Isbell
1
Purpose
1
Use
3
The site concept J.G. Speight and R.C. McDonald
5
Location
7
L.J. Gregory, R.C. McDonald and R.F. Isbell
Method
7
State or Territory
7
Coordinates
7
Topographic map sheet
9
Global Positioning System (GPS) Survey
10
Air photo reference
10
General R.C. McDonald and R.F. Isbell
13
Described by
13
Date
13
Annual rainfall
13
Type of site
13
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Australian Soil and Land Survey Field Handbook
Landform
J.G. Speight
15
Landform description
15
Description of landform element
17
Landform element key and glossary
31
Description of landform pattern
44
Landform pattern glossary
55
Vegetation
R.J. Hnatiuk, R. Thackway and J. Walker
73
Overview of the classification
75
Recognising strata
77
Formation (Level 1)
80
Structural formation (Level 2)
88
Broad floristic formation (Level 3) and subdivisions (Levels 4 to 6)
95
Examples of standard classification
102
Wetlands
103
Rainforest
109
Growth stage
120
Condition
120
Land surface R.C. McDonald, R.F. Isbell and J.G. Speight
127
Aspect
127
Elevation
127
Drainage height
128
Disturbance of site
128
Microrelief
129
Erosion
133
Aggradation
138
Inundation
138
Coarse fragments
139
Rock outcrop
143
vi
Contents
Depth to free water
144
Runoff
144
Soil profile
R.C. McDonald and R.F. Isbell
147
Type of soil observation
147
Horizons
148
Depth of horizons
156
Depth to R horizon or strongly cemented pan
156
Colour
159
Mottles and other colour patterns
159
Field texture
161
Coarse fragments
170
Structure
171
Fabric
181
Cutans
182
Voids
184
Soil water status
186
Consistence
186
Condition of surface soil when dry
189
Water repellence
191
Pans
192
Segregations of pedogenic origin
195
Effervescence of carbonate in fine earth
198
Field pH
198
Roots
199
Boundaries between horizons
199
Soil water regime
200
Substrate
J.G. Speight and R.F. Isbell
Properties of substrate material
205 206
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Australian Soil and Land Survey Field Handbook
Properties of substrate masses
210
Genetic type of substrate masses
216
Glossary of substrate mass genetic types
219
Appendix 1: Soil taxonomic units R.F. Isbell and R.C. McDonald
225
The Australian Soil Classification
225
Soil Taxonomy
227
World Reference Base for soil resources (WRB)
226
References
229
Index
240
viii
Correct citation: If reference is made to the Handbook as a whole, give reference as follows: s in text National Committee on Soil and Terrain (2009) s in references National Committee on Soil and Terrain (2009) ‘Australian soil and land survey field handbook (3rd edn).’ (CSIRO Publishing: Melbourne). If reference is made to a specific section e.g. Landform, give reference as follows: s in text Speight (2009) s in references Speight JG (2009) Landform. In ‘Australian soil and land survey field handbook (3rd edn).’ (National Committee on Soil and Terrain) (CSIRO Publishing: Melbourne). The Handbook was prepared under the auspices of the National Committee on Soil and Terrain with funding and support from CSIRO, the Natural Heritage Trust and the Bureau of Rural Sciences.
PREFACE TO THE FIRST EDITION
The use of a standard terminology for the characterisation of site attributes, such as landform and vegetation, and for the description of soils has obvious benefits for the various organisations in Australia concerned with soil and land survey investigations. Some uniformity in the description of soils has been achieved over the years with the publication of Soil survey manual (Soil Survey Staff 1951), Guidelines for soil description (FAO 1968) and, in Australia, A factual key for the recognition of Australian soils (Northcote 1971). In 1975 the Standing Committee on Agriculture established a Working Party to enquire into the nature and prosecution of soil surveys in Australia, with the aim of generating a satisfactory degree of uniformity. This Working Party was convened by Dr E.G. Hallsworth, Chairman of the then CSIRO Land Resource Laboratories, and comprised representatives of these laboratories and appropriate State and Commonwealth authorities. The Working Party recommended the formation of a National Soil and Land Survey Committee1; one of its functions would be the production of an Australian soil and land survey handbook, which would set down standards of terminology and methodology for the survey of all components of land resources. In 1976 the Standing Committee on Agriculture considered the Working Party report and requested that an Expert Panel advise further on ways of producing such a handbook. This Expert Panel, convened by Dr E.G. Hallsworth and comprising members of State and Commonwealth authorities, met in April 1977. It proposed that a committee of three should develop interim standards of soil and land classification and mapping capable of general application and produce a handbook of standard terminology and methodology. The members of the committee were R.C. McDonald, R.F. Isbell and J.G. Speight. It was originally proposed that the committee would devote not less than 12 months full time to the project. This was not possible, and the members have accordingly devoted their available time to producing this Australian soil
1
This was established as a subcommittee of the Standing Committee on Soil Conservation in 1979 and renamed Australian Soil and Land Resources Committee in 1981.
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and land survey field handbook. J. Walker and M.S. Hopkins were invited to contribute the section on vegetation. The first draft was based largely on similar handbooks, namely: s s s s
Soil survey manual (Soil Survey Staff 1951) Guidelines for soil description (FAO 1968) A factual key for the recognition of Australian soils (Northcote 1971) Soil survey field handbook (Hodgson 1974) for the Soil Survey of England and Wales s the fifth unpublished draft of the revised United States Department of Agriculture Soil survey manual s The Canada Soil Information System (Can SIS) manual for describing soils in the field (Canada Soil Survey Committee 1978). Because there was considerable divergence of approach (for example, in setting class limits) for many attributes, it was frequently necessary to judge which particular arrangement was most appropriate to Australian conditions. The first draft was sent for comment to 116 people representing all relevant organisations in Australia. The 87 replies provided a good representation of ideas. The second draft was also widely circulated and attracted a further range of comment. Because of the diversity of environments and the nature of the organisations concerned with land and soil investigations in Australia, consensus was not possible for some of the attributes discussed in this Handbook. In most such cases the majority view was adopted. The suggested field observations encompass a range in convenience of measurement and in relevance both to practical problems of land use and the scientific study of land and soil. Progress towards the establishment of a more relevant suite of attributes will depend to a degree on the use of more systematic methods in the recording of field observations, in order to permit the testing of the underlying, often unstated models. Thus, the use of this Handbook may hasten the development of more concise or more relevant field observations than those recommended in it. Such efforts to improve survey techniques must go hand in hand with efforts to discover from the clients their precise needs.
xii
PREFACE TO THE SECOND EDITION
Since the first edition in 1984 the Handbook has been widely used and adopted as a standard throughout Australia. When the publishers suggested a second edition, a request was made to relevant organisations in Australia for comments and possible modifications on the basis of field use. Numerous responses reflect the actual experiences of users since 1984. Some 23 individual replies were received, as well as three comprehensive submissions from the New South Wales Soil Data System Working Group, the New South Wales Department of Agriculture, and the Victorian Department of Conservation, Forests and Lands. The Australian Surveying and Land Information Group, Department of Administrative Services, Canberra gave useful advice on map references. While it was not possible to adopt every suggestion made, the comments have helped to make this second edition much clearer and more consistent. We thank these respondents for their assistance. In this edition a number of new sections have been added, and some rearrangements have been made to facilitate use. In particular, a much expanded chapter on substrate has been included. This should help cater to the needs of non-agricultural users. Throughout this revised edition we have tried to keep code changes to a minimum. The use of a standard terminology for the characterisation of landform and vegetation, and for the description of soils, appears to have been of benefit to scientists in Australia concerned with soil and land survey investigations. We believe that there will be an even wider acceptance of this second edition.
xiii
PREFACE TO THE THIRD EDITION
The Australian soil and land survey field handbook is a primary reference for soil scientists, ecologists, geomorphologists and students. The Handbook has been a remarkable success. During the last 25 years, consistent data have been collected on vegetation, landform and soils across Australia and the resulting databases are far more comprehensive and useful than would have otherwise been the case. Many field technicians and scientists have learnt their craft with the aid of the Handbook and it continues to sell at a steady rate. However, this success creates several significant challenges. The Handbook is essentially a measurement system for recording the attributes of landform, vegetation and soil in a semi-quantitative manner and with minimal instrumentation. Measurement systems have changed dramatically in recent years and an account of the most significant developments is provided in the new Guidelines for surveying soil and land resources (McKenzie et al. 2008). For example, digital terrain analysis has replaced some aspects of air photo interpretation and landform classification, and proximal sensing (e.g. soil spectroscopy in the visible through to the mid-infrared range of the electromagnetic spectrum) is starting to replace conventional soil description. These methods will be deployed in routine surveys during the next few years and so a completely new Handbook will be required.
Changes in this Edition Any change to the Handbook forces major overhauls of existing databases and the consequences can be far reaching and expensive. At the same time, the Handbook must reflect current technology otherwise it is destined to become irrelevant. The National Committee on Soil and Terrain faced these dilemmas when stocks of the Second Edition ran out. We knew that a complete revision of every aspect of the Handbook was needed but that new copies had to be printed immediately. We decided to publish the Third Edition only with changes that could be made with relative ease. The changes are as follows. s Most significant is revision of the vegetation chapter. As vegetation is outside the scope of the National Committee on Soil and Terrain, this xiv
Preface to the Third Edition
chapter has been guided instead by the Executive Steering Committee for Australian Vegetation Information (ESCAVI). ESCAVI has endorsed this chapter as guidelines for the collection of site-based data on vegetation in Australia. The field data collected with these new methods are currently classified, coded and named differently than in the National Vegetation Information System (NVIS) framework (ESCAVI 2003). Starting in 2008, NVIS will progressively be changed to match the classification in this chapter. Chapter 6 ‘Vegetation’ has been expanded to include wetlands, temperate rainforests, vegetation growth stage and vegetation condition. Other changes include new height classes, an increased number of broad floristic groups, and different codes for some attributes. The terms used to name vegetation units, based on their cover and broad floristic composition (Table 21), have been changed. Details of the rationale for these changes can be found in Hnatiuk et al. (2008). s Chapter 3 ‘Location’ has been updated to accommodate GPS survey and datum information. The State and Territory codes have been changed. s Chapter 5 ‘Landform’ includes new landform elements, namely: hummocky dune, barchan dune, parabolic dune, linear or longitudinal dune, risecrest, riseslope, residual rise, deflation basin, solution doline, and collapse doline.
Future changes The Fourth Edition will need to incorporate results from current research and provide guidance on several new technologies. The main challenges apparent at this stage are as follows. s The site concept which forms the basis for landform description will need revision to ensure it is consistent with contemporary methods for digital terrain analysis, spatial analysis and Earth-system science. s Gary Speight’s system for measuring and classifying landform was pioneering and many of his ideas have been incorporated into recent methods for digital terrain analysis. A new system for characterising landform is needed that takes full advantage of the new technology while retaining the link to geomorphic processes. This will be a major challenge. xv
Australian Soil and Land Survey Field Handbook
s High-resolution digital elevation models and new forms of remote sensing promise to replace the qualitative descriptors of land surface presented in this edition. Extensive testing across a range of environments is needed to identify robust descriptors. s As noted earlier, rapid advances in proximal sensing are starting to provide a practical alternative to conventional descriptions of soil morphology. Considerable field testing and further research will be needed before agreement can be reached on a new minimum data set for characterising soil profiles in the field. Database systems will require a major overhaul. s Closely related to proximal sensing is the advent of systems for automatic data entry via various forms of telemetry. Again, guidelines are required on data models, minimum data sets and transfer protocols.
xvi
ACKNOWLEDGEMENTS
Acknowledging the many contributors to the Handbook is becoming increasingly difficult. The Handbook is a collective effort and overall authorship now rests with the National Committee on Soil and Terrain. Several of the original authors have retired (Gary Speight, Joe Walker and Mike Hopkins) or sadly died (Ron McDonald and Ray Isbell) since the initial publication in 1984. However, we have retained their names on contributions that remain essentially intact. Joe Walker has also retired but he kindly contributed to the major revision of the vegetation chapter in collaboration with Roger Hnatiuk and Richard Thackway (Bureau of Rural Sciences). Linda Gregory (CSIRO) revised the chapter on site location. Specific inputs on landform and substrate were provided by David Maschmedt (South Australian Department of Water, Land and Biodiversity Conservation) and Colin Pain (Geoscience Australia). Other members of the National Committee on Soil and Terrain assisted with the production process, most notably Noel Schoknecht (Western Australian Department of Agriculture and Food) and Neil McKenzie (CSIRO). Greg Rinder expertly prepared the figures and David Jacquier helped the editorial team. Becky Schmidt (CSIRO) provided excellent editorial input to this edition. The team at CSIRO Publishing once again were exceedingly helpful and very patient. Particular thanks go to Tracey Millen, Ted Hamilton and Briana Melideo.
xvii
PU R P OSE A N D USE OF H A N DBOOK J.G. Speight and R.F. Isbell
PURPOSE This Handbook is intended to contribute to the systematic recording of field observations in Australian soil and land surveys. It attempts to: s list attributes2 thought necessary to describe adequately site and soil conditions s define these attributes consistently wherever possible with their use elsewhere in the world but giving particular emphasis to Australian conditions s define terms and categories for landform, vegetation, land surface, soil and substrate material that are based explicitly on the specified attributes s suggest codings for the various attributes, terms and categories so that concise recording systems may be developed for field use. A further purpose of the Handbook is to provide a factual database from which interpretations can be made. Field observations provide the basis for predicting the consequences of land use. These may be supplemented by data 2
No distinction is made between the word ‘attribute’ and the word ‘property’ used in the Soil Profile section. Both mean ‘characteristic’ or ‘trait’. ‘Attribute’ includes ‘variable’. Observations produce values of attributes or properties.
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Australian Soil and Land Survey Field Handbook
from air photos, maps, records, laboratory analyses, experiments, local information and so on. The chain of inference for making such predictions has been clearly established in only a few instances, evidence that perhaps the weakest link is the collection of relevant field data. This Handbook was prepared to meet the needs of somewhat diverse surveys. The Handbook covers a range of soil surveys, typically at medium and small scales, and ‘land system’, ‘land unit’, ‘biophysical’, ‘ecological’ and ‘environmental impact’ surveys, whether for agricultural, recreational, industrial, residential or other purposes such as a general scientific inventory. The observations proposed are relevant to surveys at diverse scales, although surveys at very large scales commonly demand both more detailed observations, and also observations of particular attributes that probably have not been included here. At such large scales, many attributes of the site that surrounds each point of soil observation may be uniform over most of the points, and thus is of little interest within the context of the given survey. However, if site attributes are recorded for at least a few of the observation points, they may prove extremely valuable in later correlative work. The recording of attributes of the site and adjacent landforms has two distinct purposes. First, the attributes may be directly relevant to land use – for example, to ploughing feasibility, earthmoving costs, erosion hazards, scenic resources and costs of clearing. Second, the attributes are a link between the hidden physical and chemical properties of the soil, regolith or bedrock, for which data will always be scarce, and the visible properties of landform, surface material, and vegetation that may be more readily mapped and catalogued. Site attributes link to other attributes both within a site and beyond it. Attributes are intended to be correlated with soil and other subsurface properties observed at the site in order to discover significant relationships between them. Relationships implied in some surveys have lacked adequate support (Bleeker and Speight 1978; Chittleborough 1978). Better validation is required to justify extrapolative mapping and the setting up of land units or land components. The site data, however, are intended to establish local ‘ground truth’ values for the landform, surface material and vegetative properties that contribute to the more extensively developed characteristic image, ‘signature’, or pattern on an air photo or other remote-sensing record.
2
Purpose and Use of Handbook
USE The Handbook is designed as a reference to attributes needed to describe systematically the site and soil conditions related to landform, vegetation, land surface, soil profile and substrate materials. The glossaries and definitions of terms will provide a uniform understanding of the meaning of words used in field notes, in discussion and in publications. This will enhance communication. The attributes are to form the basis of lists to be used for specific surveys. When developed, these lists will provide sufficient information to support the survey conclusions. For each attribute, there is a suggested scheme of classes, but this does not preclude the observation and recording of actual numerical values where feasible. Suggested code letters and numbers for each attribute described appear in red. Not all conceivable soil properties are provided for and hence some properties may need to be recorded, if desired, in free format – for example, orientation of mottles. All dimensions are expressed in SI units. The attributes to be recorded in a specific survey will depend on its purpose and scale and will be decided upon by the organisation conducting the survey. In reconnaissance surveys, fewer site and profile attributes will be described than in high-intensity surveys. For detailed site and profile descriptions such as those required for pedological research, descriptions of agronomic research sites or in the legend-making stage of detailed surveys, most of the attributes given in this Handbook will be recorded, if present. It is important that sites and profiles be described as they are and not as they may have been. Sites and profiles should be described as factually as practicable but genetic inferences are inevitable. Where genetic inferences are used, the basis of the inference should be noted so the user is aware of assumptions made. The field observations are for the descriptions of sites (page 5) and not for soil classes or for aspects of mapping units that are better recorded in the office rather than in the field. Although diagnostic horizons necessary for particular soil classification systems, for instance Soil Taxonomy (Soil Survey Staff 1975), are not included, the field observations recorded may be used to classify soil in this or in any other soil classification scheme. Coding for soil classification schemes most likely to be used in Australia is given in Appendix 1.
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Australian Soil and Land Survey Field Handbook
Most of the attributes of soil to be observed, horizon by horizon, are widely accepted among pedologists. However, there are some that do not have direct relevance to land use; rather, they serve as surrogates for properties that are impractical to observe or measure routinely.
4
T H E SI T E C ONC E P T J.G. Speight and R.C. McDonald
A site is a small area of land considered representative of the landform, vegetation, land surface and other land features associated with the soil observation. The extent of a site is arbitrary but certain dimensions are appropriate for certain attributes. Observe landform element attributes over a circle of 20 m radius (1256 m 2) and landform pattern attributes over a circle of 300 m radius (28.3 ha). Sample vegetation in a square or rectangular site of 400 m2. In sites dominated by ground layer, several 20–50 m2 samples or 10–20 m transects are used. Observe most land surface attributes within a site 10 m in radius (315 m2); these attributes are: slope, aspect, disturbance of site, microrelief, surface coarse fragments, rock outcrop and runoff. A few land surface attributes refer simply to the point of soil observation, namely elevation, drainage height and depth to free water; the attributes erosion, aggradation and inundation refer to the larger 20 m radius site used for landform element attributes. In some instances a soil observation may be representative only of a soil body smaller than 10 m in radius. For example, in some gilgai the vegetation, land surface and soil all differ between the mound and depression. In such instances the extent of the site for those features is only that of the mound or the depression.
5
LOC AT ION L.J. Gregory, R.C. McDonald and R.F. Isbell
METHOD Record the method used to acquire the coordinates. R G S
Map reference GPS Survey
STATE OR TERRITORY Record the code as follows for the State or Territory in which the site is described. These codes have been changed from McDonald and Isbell (1990). 1 2 3 4
NSW VIC QLD SA
5 6 7 8
WA TAS NT ACT
COORDINATES Datum Record the datum of the coordinates. Older maps will generally be based on the Australian Geodetic Datum of 1966 or 1984 (AGD66, AGD84), while current maps should be based on the Geocentric Datum of Australia (GDA94). If you
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Australian Soil and Land Survey Field Handbook
are obtaining coordinates from a Global Positioning System (GPS) unit, the native datum is the World Geodetic System (WGS84). However, this may not be the display default so check the settings. For further information, see the Geocentric datum of Australia technical manual (Intergovernmental Committee on Surveying and Mapping 2002). AGD66 AGD84 GDA94 WGS84
Australian Geodetic Datum 1966 Australian Geodetic Datum 1984 Geocentric Datum of Australia 1994 World Geodetic System 1984
Projection State whether the coordinates are projected or geographic. M
Projected by Universal Transverse Mercator system Geographic (latitude and longitude)
L
Projected Most topographic map sheets are projected onto the Universal Transverse Mercator (UTM) coordinate system. In Australia, this will be called the Australian Map Grid (AMG) or the Map Grid of Australia (MGA) depending on the datum used. The easting and northing coordinates taken from these sheets will have 6 digits and 7 digits respectively. The zone will also be required (49–56 in Australia). Do not use the Universal Grid Reference notation.3
Geographic When using a GPS or a regional map, record coordinates in latitude and longitude. Record southern hemisphere latitudes as negative.
Easting, northing, zone Record easting and northing UTM projected coordinates, when reading from a topographic map. Give a 6-figure easting, a 7-figure northing and a 2-figure grid 3
The Universal Grid Reference (National Mapping Council of Australia 1986) uses a zone designator and 100 000 metre square identification along with a reduced set of digits. The example given in the section ‘Easting, northing, zone’ (see page 9) would be recorded as 55HFA9208494905 (‘55H’ is the zone designator while ‘FA’ is the 100 000 metre square identification).
8
Location
zone (49–56 in Australia), as accurately as map scale permits. Location of the central point of a site on a map is unlikely to be much more accurate than 1 mm on the map (i.e. 10 m on a 1:10 000 scale map, or 100 m on a 1:100 000 scale map). Example: Zone 55
Easting 692084
Northing 6094905
Latitude and longitude Coordinates may be given in degrees, minutes and seconds (DMS) where a location is read from a small-scale (regional) map. When locating with a GPS, record the coordinates in decimal degrees (DD) to five places to obtain a precision to the metre. Latitudes (giving the north or the south part of the coordinate) will be negative in Australia. Example: Latitude –35.27058
Longitude 149.11181
TOPOGRAPHIC MAP SHEET Give map sheet details regardless of the method used to obtain the coordinates. This will provide a cross-check for attribute accuracy. At scales larger than 1:100 000, use the numbering system for the State or Territory in which the survey is conducted.
Map scale 1 2 3 4
1:1 000 1:2 500 1:5 000 1:10 000
5 6 7 8
1:25 000 1:50 000 1:100 000 1:250 000
Map sheet number and map sheet name Give number and name on the map, for example:
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Australian Soil and Land Survey Field Handbook
Map scale Map sheet number Map sheet name
8 SH 50-15 Kellerberrin
7 8525 Kosciuszko
6 8727-III Canberra
GLOBAL POSITIONING SYSTEM (GPS) SURVEY Record the GPS survey method used to obtain the coordinates and estimate the accuracy. Make sure you also record the datum and projection settings in the appropriate section. Submetre accuracy is usually obtained only through the use of differential techniques. Autonomous (single unit) methods can obtain
