Chapter

7

By Soil Science Division Staff. Revised by Jim Fortner, USDA-NRCS.

Soil Survey Data Collection, 

Management, and 

Dissemination

Introduction

During the course of a soil survey, a large amount of data, of various 

types and in various formats, is commonly collected or developed. 

These data include, but are not limited to, field notes, soil profile 

and landscape descriptions, drawings, laboratory data, photographs, 

descriptions of soil map units and map unit components, and, of course, 

the basic soil map. 

Before a soil survey project begins, a decision must to be made as 

to what type of system is going to be used to collect, store, manage, 

and disseminate the information to be gathered and/or developed. For 

example, the data and information may be maintained and distributed 

as hard copy, in electronic form, or by some combination of the two. 

Deciding how to manage these data can be a daunting task, but it is a 

very important one.

First, a few questions need to be answered: 

• What is the purpose of the soil survey? 

• For whom is the information intended? 

• Is the information to be publicly available to anyone that wants 

it, or is it to be kept within the organization that is conducting 

the soil survey? 

• What types of products or output will need to be generated at the 

end of the project? 

• In what format are the products to be made available—electronic 

or hard copy, or both? 

• Do the end users of the information only need the summarized 

soil survey data, or will they also need access to the various pieces 

of point data collected at individual points on the landscape? 
396 Chapter 7

• Will the data and/or generated information be delivered via the 

Internet? 

• What resources and expertise are available for maintaining and 

disseminating the data?

The answers to these and other questions will help determine what sort 

of system is needed.

To begin this discussion, a distinction needs to be made between 

“soil data” and a “soil information system.” Soil data refers to the actual 

data that are collected or generated during the course of a soil survey. A 

soil information system includes not only the data, but also the various 

methods and/or systems used to collect, store, and manage the data and 

resulting interpretations and information and to disseminate them to end 

users.

A database can be defined as “a collection of information or data that 

is organized so that it can easily be accessed, managed, and updated.” 

In its crudest of forms, a database can be a collection of paper copies 

maintained in a file cabinet or box. With a crude database, the ease of 

accessing, managing, and updating such data is limited. In electronic 

format, a database is generally a series of related data tables maintained 

within some database management software (DBMS) on a computer. 

The data can be both tabular data (which describes the characteristics 

and proportions of soils in the soil survey area) and spatial data (which 

contains the locations of soil map unit boundaries and site locations 

where specific soil samples and soil profile descriptions were collected 

and other field observations were made, as well as other thematic data 

layers).

If the decision is made to collect, store, and manage soil survey 

data in hard-copy format, the options for product delivery are minimal. 

If the decision is made to use an electronic format for data collection, 

storage, and management, then some type of electronic database(s) 

will be needed. There are numerous options for dissemination of data 

maintained in electronic format.

Automated Data Processing in Soil Survey

A powerful tool for handling accumulated soil survey data is 

automated data processing (ADP), which uses computers with wordprocessing, database, spreadsheet, statistical, geographic information 

system (GIS), and other specially designed software packages. ADP 

facilitates data collection and entry, data editing, and timely summaries, 
Soil Survey Manual 397

comparisons, and analyses of data that otherwise would be impractical 

or impossible to do. It enables frequent and inexpensive updating of long 

lists, such as lists of soil series for various geographic regions, in any 

order or sequence, and other output products. The summaries can provide 

information to guide important policy decisions. ADP can quickly 

perform routine and otherwise time-consuming computations. It allows 

for easy editing of descriptive materials, manuscripts, and narrative or 

tabular data and information.

In recent years, with the increased use of computers and the 

development of computer applications such as geographic information 

systems, more and more soil survey data are being delivered to end users 

in electronic or digital format (see chapter 5). Data also are, at least 

partially, being collected and recorded in electronic format in the field 

using a variety of tools (see chapter 6). Managing the data in digital format 

allows greater flexibility in data delivery. Products can be delivered to 

users in either hard-copy or electronic formats. The remainder of this 

chapter will be primarily devoted to the electronic format of soil data 

management and delivery. 

Soil scientists need to know the fundamentals of ADP just as they 

need to know the fundamentals of chemistry, botany, geology, mathematics, economics, and other subjects that support the work of soil survey. 

Literature on the fundamentals of ADP is readily available. Automated 

data processing can be used for many soil survey tasks, but this does not 

mean that it should be used for all of them. Before any decision is made 

to use ADP, an objective study (systems analysis) is needed to determine 

what combination of equipment, personnel, and other factors will be the 

most useful and economical. The selection of any new system must take 

into account its compatibility with systems used by cooperating agencies 

to handle soil survey data and related physical and environmental data. 

Many combinations of computers, storage media, input-output devices, 

and communication facilities are possible.

Even after an ADP system has been designed and implemented, 

continuous study, testing, and improvement are needed. ADP technology 

is changing rapidly, and new equipment and new procedures are being 

developed constantly. As experience is gained, an existing system may 

need to be improved or replaced.

Automated data processing can manipulate data in many ways. 

Because most of the data are likely to be needed in different combinations, 

the basic use of ADP will probably be data storage and retrieval. For this 

use, precisely and consistently defined records need to be entered into 

some medium readable by computers and arranged in cataloged files. 
398 Chapter 7

These files of soil records are collectively referred to as a soil survey 

database. 

Databases can be distributed between multiple locations or kept in 

a centralized system, depending on system requirements and facilities 

available. For example, in the early versions of the National Soil 

Information System (NASIS) used by the U.S. National Cooperative 

Soil Survey (NCSS), the database was divided (distributed) among 17 

regional databases and each region managed soil survey data for their 

respective area. In later versions of NASIS, the database was merged 

(centralized) into a single national database. Currently, all users access 

the single database to create and manage the data for which they are 

responsible. A uniform coding system is essential for a consistent format 

of the data. It permits direct transfer and sharing of data and the use of 

computer programs to manipulate the data. 

Databases can also be classified as transactional or publication. In

transactional databases, ongoing edits and additions are made to the 

data. Generally, these databases are used only internally by members of 

the organization responsible for the database. NASIS is a transactional 

database. In publication databases, the database content is certified and 

made available to the public. The NCSS’s Soil Data Mart is a publication 

database.

After soil information has been systematically entered into the 

database and the necessary equipment and operating instructions have 

been organized, the data are available for many kinds of operations. 

Computer programs (software) may need to be developed if they do not 

already exist. Software development is typically the most expensive and 

time-consuming aspect of data processing. A good data management 

system can reduce the amount of software needed. Important applications 

for soil survey include:

1. Answering questions. Examples are: What soils have certain 

sets of properties? What soils are mapped in specified localities? 

What soils will produce corn yields of more than 100 bushels 

per acre (approximately 6,700 kilograms per hectare) under a 

particular management system?

2. Performing statistical studies, particularly multiple correlations, 

for many purposes, including testing the numerical limits of values 

in Soil Taxonomy, determining what soil properties observable in 

the field correlate well with laboratory results, and determining 

what observable soil properties reliably indicate soil behavior. 

3. Preparing summaries (e.g., summaries of interpretations by soil 

families, phases of soil families, subgroups, etc.; summaries 
Soil Survey Manual 399

of the extent of the different soils in various geographic areas; 

summaries of the number and extent of soils having selected 

features such as a fragipan).

4. Arranging and printing out tabular material for soil survey 

manuscripts and other reports (see appendices). Text that is 

repeated in published surveys of a given State or region can be 

stored in finished form and reused as needed.

5. Storing and easily updating lists, such as the classification of soil 

series.

6. Generating interpretive maps and printing them on demand (see 

appendix 4). This application is becoming increasingly valuable 

for soil management and land use planning.

Users of ADP outputs must be aware of the importance of reliable 

and accurate original information. High-quality data must be entered at 

the outset. ADP cannot improve the quality of the data; only people can. 

However, it can be a valuable tool in finding data inconsistencies.

To store soil survey data in electronic format, one or more electronic 

databases are needed. These databases can become very complex, 

depending on how many soil attributes are to be recorded and stored and 

to what degree of resolution or frequency the data are to be collected. 

Database design is an important consideration. A database can 

succeed or fail because of data consistency or the lack thereof. Standards 

need to be established to help ensure data consistency. It is important 

that the various tables and attributes or columns within the database be 

sufficiently defined so that there is no ambiguity as to what information 

is to be recorded in each table and/or column and in what format. This 

information describing the database, referred to as “metadata,” needs to 

be made available to those individuals who are collecting and inputting 

the data into the database as well as to end users. The metadata can 

prevent the misunderstanding and misuse of the resulting soil data. 

The electronic database can also employ a variety of data validation 

tools and rules to help ensure data integrity and data quality. For example, 

the database can allow only numeric values to be entered into a data field 

that is defined as requiring a numeric entry. The system can ensure that 

only values within a particular numeric range be entered (e.g., only values 

between 1 and 14 are allowed for pH). Choice lists can be developed to 

ensure that only approved terms are used for specified data elements and 

that data entries are consistently spelled. 

The actual design and structure of the database is somewhat 

dependent on the type(s) of data being collected and/or needing to be 

stored and delivered to end users. It can also vary somewhat based on 
400 Chapter 7

the database management software (DBMS) that will be used to manage 

the database. 

Standard methodologies or protocols for data collection are needed to 

ensure that data collected from different locations, at different times, and 

by different people can be appropriately combined and summarized or 

evaluated as needed. For example, slope should be measured in the same 

way and clay content should be determined using the same procedures 

throughout the survey area.

Recording Data and Information—Field and Lab

Information gathered during the course of a soil survey is recorded 

in a variety of formats and content. In addition to the basic soil map, 

important forms of data include field notes, soil profile descriptions, 

laboratory analytical results, photographs, and drawings. These forms 

of information work together to ensure a quality survey. The data fall 

into three basics categories: point data, aggregated data, and spatial data. 

Each category is discussed in more detail in the following paragraphs.

Point Data

Point data are data that are collected, measured, or observed at a 

particular geographic location in the field. They generally record a single 

value for each attribute recorded about the soil map unit as a whole, or 

an individual soil map unit component, and the landscape in which it 

occurs. At a specific geographic location at a particular point in time, 

each attribute only has one value. Attributes may include slope, landform 

setting, depth to each soil horizon, pH or texture of each horizon, etc. 

Also included in point data are photographs taken at the sample location 

and sketches and drawings of the landscape and/or soil profile. Point data 

can be the results of direct field observations or measurements, analytical 

result of laboratory measurements from soil samples collected at the 

location, or the results from ongoing monitoring tools that collect data 

(such as soil temperature or soil moisture content) at regularly scheduled 

intervals.

Each piece of point data collected should include a reference to the 

soil map unit and/or soil map unit component that it represents. This is 

a part of the correlation process that takes place during the course of 

the soil survey project (see section titled “Correlation Steps” in chapter 

4). The system developed to manage soil survey data needs to have the 

capability to manage all forms of point data that will be collected.
Soil Survey Manual 401

Soil Map Units vs. Soil Map Unit Components

When conducting a soil survey, the areas outlined on the soil map 

represent a segment of the natural landscape and are generally referred 

to as a map unit polygon or delineation. Each polygon is labeled with 

a map unit symbol that indicates which soil map unit it represents. It 

displays the extent of the soil map unit on the landscape and is defined 

as a collection of soil types that occur together in a regularly repeating 

pattern on the landscape. Each soil type within a particular soil map unit 

is referred to as a soil map unit component. The soil map unit component 

generally comprises approximately the same proportion of the map unit 

in each polygon of the soil map unit (e.g., for soil map unit “10,” soil 

component A makes up 75% of the map unit, soil component B makes up 

15%, and soil component C makes up 10%). Map units rarely are 100% 

composed of any particular soil type. 

The level of detail of each map unit component is generally dependent 

upon the scale at which the soil map is being developed. Small-scale 

maps (e.g., those at 1:100,000) generally will have more broadly defined 

map unit components than larger scale maps (e.g., those at 1:12,000). For 

a more detailed discussion of soil map units and map unit components, 

see chapter 4.

Field Notes

Field notes include soil profile and landscape descriptions, 

descriptions of the relationship and interactions between soil components 

or map units, information on the behavior of the soils, and inferences 

about how the soils formed. The information delivered to end users to 

accompany the soil maps for each soil survey is developed based on the 

field notes. Field notes are used for preparing standard definitions and 

descriptions of soil series, soil map units, and map unit components and 

for correlating soils in the national program. They are as important as the 

map base on which soil map unit boundaries are plotted.

The best notes are recorded while field observations are fresh in the 

mind of the observer. For example, the description of a soil profile is 

recorded as it is being examined. Information from a conversation with 

a farmer is recorded during the conversation or immediately thereafter. 

Unless notes are recorded promptly, information may be lost. All field 

notes should be clearly identified. The survey area, date, location, and 

author are necessary for each note. Each note should be related to an 

identified soil map unit or map unit component. The source of the 

information, if not from direct observations, should also be identified. 
402 Chapter 7

To be available and useful, field notes must be organized and stored 

in a standardized manner. Electronic storage is a good solution. Notes 

that are handwritten in the field can later be scanned and stored in a 

computer database. Notes can also be recorded on handheld devices 

using word-processing or note-taking computer software in the field, 

and the resulting files stored in a standardized file folder structure on the 

computer.

Field notes must be understandable to all survey personnel. Shorthand 

notes need to be transcribed to standard terminology. Only common 

words and expressions, as found in a standard dictionary or technical 

reference, should be used.

The most important notes record the commonplace, such as the 

extensive kinds of soils and their properties, the common crops or 

vegetation, the performance of septic systems, etc. The tendency to 

record anything other than the commonplace should be avoided, because 

subsequent efforts to prepare a descriptive legend or make interpretations 

from such notes will be unsuccessful. However, in the early stages of 

a soil survey project, differentiating between the “commonplace” and 

“oddities” may be difficult. As work in the survey area progresses, what 

appear to be oddities in the beginning may later become commonplace as 

other parts of the survey area are mapped. Field notes should indicate how 

closely something represents the commonplace. Survey personnel must 

first learn to see and record the commonplace, then identify departures 

from the usual.

Field notes record observations as well as complete descriptions 

of pedons at specially selected sites. Notes that are made during daily 

mapping typically are not full descriptions. They may record only color, 

texture, and thickness of major horizons as seen in auger cores. This 

information is used to supplement detailed examinations. Notes of this 

kind are especially important for soils that are not well known and for 

soils of potential, but questionable, map units.

Field notes include information about the relationship of map units 

and map unit components to one another, to landforms, and to other 

natural features. The setting of a soil—its position in the landscape—is 

important. Landscape features strongly influence the distribution of soils. 

The properties and extent of the soil and the location of soil boundaries 

can be deduced from the landscape. The kind of landform or the part 

of the landform that a particular soil occupies and how the soil fits into 

the landscape should be described. Soil patterns and shapes of soil 

delineations are important in relation to large-scale soil management. 

Landscape identification is discussed in chapter 2.
Soil Survey Manual 403

The kinds and amounts of the various soil map unit components 

in each map unit, as well as their positions in the landscape, are noted 

and recorded during fieldwork. The soil map unit components are either 

identified by name or their contrasting properties are described. Although 

the kinds and amounts of map unit components vary somewhat from 

delineation to delineation, an experienced surveyor has little difficulty in 

maintaining an acceptable level of interpretive purity within a soil map 

unit. This is due to the fact that most contrasting map unit components 

(i.e., dissimilar soils and miscellaneous areas) occupy specific, easily 

recognized positions in the landscape. If a precise estimate of the 

taxonomic purity of a given delineation is needed, special sampling 

techniques, such as line transects or point intercept methods, are required.

Notes should be made on soil erosion in particular map units. They 

could include descriptions of eroded areas, degrees of erosion within and 

between soil phases, differences in variability among soils and landscape 

positions, extent of soil redistribution and deposition in map units, and 

effect of erosion on crop yields and management of the soil.

Soil behavior concerns the performance of a soil as it relates to 

vegetative productivity, susceptibility to erosion, and a particular land 

use (such as a foundation for houses or a waste disposal site). Notes 

on soil behavior, unlike those on the nature and properties of the soil, 

are obtained largely from the observations and experiences of local land 

users. Direct observations by field scientists and inferences made from 

them should be labeled as such.

Notes on behavior focus on the current and foreseeable uses of the 

important soils in an area. For example, if range is the primary land use in a 

survey area, information on range production along with plant community 

descriptions may be needed for all of the soils of the area. Notes on the 

performance of soils under irrigation, however, would probably be needed 

as well as where the soils are irrigated or may be irrigated in the future. 

Information on probable forest growth and plant community descriptions 

might be pertinent to the purposes of the survey even though it comes 

from the experience of only a few individuals or a few kinds of soils. An 

area with a rapidly expanding population needs data on the engineering 

performance of soils, such as how well the different soils would support 

houses, what kinds of subgrades would be required for streets and roads, 

and whether onsite waste disposal systems would function satisfactorily.

Valuable information about the performance of soils can be obtained 

from observations made in the field while surveying. Soil scientists can 

see poor crop growth on a wet soil or in an eroded area. They note the 

failure of a road subgrade or of an onsite waste disposal system in specific 

kinds of soil. However, data on yields and management practices for 
404 Chapter 7

specific crops typically come from farm records or experimental fields. If 

records are not available, such as records that compare crop productivity 

between eroded and uneroded phases of a soil, special studies and data 

collection may be needed. 

Information on forest growth or range production and the composition 

of a vegetative plant community also is commonly derived from 

observations made by others, but it can be supplemented by information 

recorded by the soil scientist. Most information on the engineering 

performance of a soil comes from people who work with structures and 

soil as a construction material. During fieldwork, a special effort should 

be made to obtain this kind of information from knowledgeable people.

The source of information about soil behavior is evaluated and 

recorded in the field notes. Inferences are to be clearly distinguished 

from observations of soil morphology, vegetation, landform, etc. Most 

notes about how soils formed, for example, are inferences. The condition 

of growing crops is observable, but statements about soil productivity 

based on such observations are inferences. That some soil material is 

nearly uniform silt loam and lacks coarse fragments is directly observed; 

the conclusion that the soil formed from loess is inferred. Theories 

formed on the basis of inference should not unduly influence the choice 

of observation sites or the properties to be observed.

Soil Profile Descriptions

Soil profile descriptions are basic data in all soil surveys (see chapter 

3 for a detailed discussion). They provide a major part of the information 

required for correlation and classification of the soils of an area. They 

are essential for interpreting soils and for coordinating interpretations 

between soil survey areas. The soil descriptions and the soil map are the 

parts of a soil survey project that have the longest useful life.

Field descriptions of soil profiles range from partial descriptions of 

material removed by a spade or an auger to complete descriptions of 

pedons seen in three dimensions (from intersecting pits where horizontal 

layers were removed sequentially from the surface downward). Because 

most field descriptions of soil profiles are the former, care in making 

them is essential.

Field descriptions should include, but are not limited to:

• The date, time of day, and weather conditions;

• The name of the describer;

• The geographic location of the site;

• Observed external attributes of the pedon, such as landscape 

position, landform, and characteristics of slope;
Soil Survey Manual 405

• Inferred attributes of the pedon, such as origin of soil parent 

material and the annual sequence of soil water states;

• The plant cover or land use of the site;

• Observed internal properties of the pedon, such as horizon 

thickness, color, texture, structure, and consistence;

• Inferred genetic attributes of the pedon, such as horizon 

designations and parent material;

• Inferred soil drainage class; and

• The classification of the pedon in the lowest feasible taxonomic 

category.

The degree of detail that is recorded is somewhat dependent upon 

whether the description is intended to provide a complete soil profile 

description for comparisons with other pedons placed in the same 

taxonomic class or simply to determine the variation of a selected 

property within a taxon. One should keep in mind that the majority 

of the time and expense in collecting a description is in finding and 

getting to the sample site and exposing the soil profile. It is much more 

economical to get a complete description during the initial visit than 

to return to the site later. This is especially true when mapping remote 

areas.

The attributes of pedons, procedures for describing their internal 

properties, and standard terminology are described in chapter 3. When 

standard terms are not adequate to characterize all properties and 

attributes of a soil, common descriptive words are used.

Standard Forms and Terminology

Standard forms are useful for recording the observations and data 

required in a soil survey. They permit recording of information in a 

small space. A standard form used to record soil profile descriptions is 

illustrated in figure 7-1. This is merely an example; no standard form 

can cover all situations. Forms require modification as more is learned 

about soils and how to evaluate data. They can be automated to permit 

electronic recording of the information and limit the need for later data 

entry. Handheld computers can be programmed, following a standard 

format, to allow soil information to be entered by workers while in the 

field. The information can be uploaded later to a computer in the office 

or to a central database. The office computer can be used for storage 

of information, sorting, and printing out descriptions. Automated forms 

can avoid data transcription errors that occur during data entry, thereby 

improving data quality.


408 Chapter 7

A standard form can serve as a checklist of characteristics that 

should be recorded. A checklist is especially valuable for beginning soil 

scientists because it reminds them to record, at minimum, data for the 

listed properties. Observations, however, should not stop with the listed 

properties. There is a strong tendency to record the information required 

by the form and no more. Thus, a form designed to set a minimum on the 

amount of information recorded also tends to set a maximum. Good soil 

profile descriptions typically require information beyond that needed to 

complete the form. Free-form notes are commonly used for this purpose.

Standard forms are useful for recording the day-to-day observations 

made during mapping. Many such notes are not full descriptions of 

pedons. These abbreviated descriptions typically can be made on a 

standard form more easily than they can be written in narrative form. 

Abbreviated notes are also useful in recording many observations during 

field reviews and when transecting. For these and similar purposes, 

the forms make note-taking easier and lessen the risk of recording an 

inadequate description. Complete descriptions of pedons, such as those 

made when soils are sampled for special studies or those of the typical 

pedons of soil series or map unit components, generally require a more 

comprehensive form or recording device so that all characteristics can be 

adequately described.

Standard forms, whether in hard-copy or electronic format, generally 

require the use of abbreviations or symbols due to limited space. These 

abbreviations or symbols should follow a standard format so that the 

recorded information can be readily and accurately interpreted by others 

and correctly transcribed to standard terminology. The codes in the Field 

Book for Describing and Sampling Soils are examples (Schoeneberger et 

al., 2012).

All soil profile descriptions, regardless of their completeness or the 

format in which they are recorded, should become a part of the permanent 

record of the soil survey area so that they are available for use by others. 

Photographs

Photographs are a significant component of soil survey data 

collection and documentation. They can illustrate important things 

about an individual soil or a soil catena in soil survey reports, scientific 

journals, textbooks, and periodicals. They can be included in any 

electronic presentation of soil survey data to end users. Good photographs 

provide records and reference sources of basic soil information. Taking 

photographs needs to be planned early in the soil survey.
Soil Survey Manual 409

Photographs that include a scale are useful in estimating volume, 

area, or size distribution. The comparison of coarse fragments in a soil 

against photographs of known quantities of coarse fragments improves 

the reliability of estimates. Similar photographic standards can be used to 

estimate volume or size of nodules and concretions, mottles, roots, pores, 

and rock fragments. In a similar manner, photographic standards can be 

used in estimating area or the special arrangement of surface features and 

land use.

Equipment for Field Use

A good-quality camera is important in obtaining high-quality photos. 

Digital cameras are the general norm today. A digital camera allows the 

image file, along with its respective metadata, to be stored in a database 

file system for later use. The camera needs to provide resolution greater 

than 8 megapixels (at least 16 megapixels is preferred) to produce 

high-quality images. The ability to vary the aperture and exposure time 

settings is desirable. Many of the larger point-and-shoot cameras and 

35-mm single-lens reflex digital cameras are adequate. 

A tripod is generally necessary, especially at shutter speeds below 

1/50 second. It reduces camera movement and enables the photographer 

to concentrate on composition and focus. A flash is needed in some 

poorly lighted situations or to eliminate shadows.

Certain other items are necessary for good pictures of soil profiles. 

A scale that indicates horizon depth or thickness is important. A scale 

that does not contrast greatly with the soil, such as an unvarnished and 

unpainted wood rule or a brown or khaki colored cloth tape that is 5 cm 

by 2 m works well. Large black or yellow figures at 50-cm intervals, 

large ticks at 10-cm intervals, and small ticks at 5-cm intervals complete 

the scale. A perfectly vertical scale increases the quality of the photo, in 

contrast to a tilted scale.

A small spatula, kitchen fork, or narrow-bladed knife is useful in 

dressing the soil profile. Paint brushes of various widths and a tire pump 

can help clean dust from peds. A sprayer can be used to moisten the 

profile when necessary.

Photographing Soil Profiles

Careful planning is essential for obtaining high-quality photographs 

of soil profiles. A representative site is selected on a vertical cut face or 

in an area where a pit can be dug large enough for adequate lighting of 

all horizons and for the camera to be 1.5 to 2.5 m from the profile. The pit 

or cut face should be oriented so that the maximum amount of light will 

strike the prepared face at the proper angle when photographed. Better 
410 Chapter 7

images are generally obtained when the soil profile is either in full sun 

or full shade. Subtle differences in soil color are often more apparent on 

cloudy days than in full sun. Direct exposure to full sunlight often results 

in a washed out image.

The profile needs to be properly prepared to bring out significant 

contrast in structure and color between the soil horizons. Beginning at 

the top, fragments of the soil can be broken off with a spatula, kitchen 

fork, or small knife to eliminate digging marks and expose the natural 

soil structure. Dust and small fragments can be brushed or blown away. 

Moistening the whole profile or part of it with a hand sprayer helps to 

obtain uniform moisture content and contrast.

Every profile should be photographed three or four times with different 

aperture settings, angles of light, and exposure times. Notes should be 

made immediately after each photograph is taken to record location and 

date, complete description of the subject, time of day, amount and angle 

of light, camera setting, method of preparing the profile, and other facts 

that are not evident in the photograph. Besides increasing the ways the 

photograph can be used, good notes provide information for improving 

technique. If possible, a landscape photograph should accompany the 

soil profile photograph.

Photographing Landscapes

Landscape photographs illustrate important relationships between 

soils and geomorphology, vegetation, and land use and management. They 

should be clear and in sharp focus and have good contrast. Photographs 

representative of the area being mapped are the most useful.

The most important thing in landscape photography is lighting. The 

best pictures are made at the time of day and during the time of year 

when the sun lights the scene from the side. The shadows created by this 

lighting separate parts of the landscape and give the picture depth. If the 

sun is at a low angle to the horizon, shadows are generally amplified and 

give an image more contrast and depth. Photographs taken at midday or 

with direct front lighting can lack tonal gradation and, therefore, appear 

flat. Photographs taken on overcast days can have the same problem. A 

small aperture should be used to gain maximum depth of focus.

Photo composition is important. A good photograph has only one 

primary point of interest. Objects that clutter the photograph (e.g., 

utility poles, poorly maintained roads and fences, signs, and vehicles) 

detract from the main subject. The point of interest should not be in the 

center of the photograph. The “rule of thirds” for composition is useful 

when looking at the scene through the viewfinder. The image area can 

be visualized as divided into thirds both horizontally and vertically. 
Soil Survey Manual 411

The center of interest should be one of the four points where these lines 

intersect. Sky should make up less than one-third of the image, and the 

camera should be kept level with the horizon. In addition, landscape 

photographs should be taken from a variety of angles (e.g., from a 

kneeling position, on a ladder, on top of a car or low building, etc.).

Close-up Photography

Many soil features, such as peds, pores, roots, rock fragments, 

krotovinas, redoximorphic features, concretions, and organisms, can be 

photographed at close range. The minimum focusing distance for most 

cameras used in the field allows small features to be photographed. Many 

cameras have a built-in macro focus feature that enables focusing within 

a few inches. Macro lenses are available for most 35-mm cameras. 

Close-up attachments for conventional lenses are also available. As 

with landscape photography, the lighting angle is important. Direct front 

lighting tends to blend texture, separation, and contrast in the photograph.

Photographing clay films and other minute soil features requires 

special equipment and techniques of photomicrography that are outside 

the range of this manual.

Metadata

For each photograph, metadata should be recorded, including the 

date of the photo, the geographic location, a description (caption) of what 

the image is intended to show, and a reference to the map unit(s) and soil 

components of the area. 

Aggregated Data

Aggregated data capture the ranges of various physical and chemical 

properties of soil map units as a whole and individual soil map unit 

components. They include the descriptions of each soil map unit and 

map unit component; the detailed physical, chemical, and morphological 

attributes of each soil; and descriptions of the relationship of one soil 

map unit to another on the landscape. Aggregated soil property data 

generally are the data used to generate interpretive ratings for each map 

unit and its components. 

Aggregated data are developed by summarizing the various pieces of 

point data that have been collected during the soil survey and referenced 

to a particular soil map unit or map unit component. Values for a particular 

soil property are commonly expressed as a range. Depending on mapping 

scale, map unit design, and the level of specificity of data needed for the 

purpose of the soil survey, the upper and lower limits and, in most cases, 
412 Chapter 7

a representative value (RV) of the range of each soil property need to be 

stored in the database (e.g., clay content ranges from 18 to 27%, with an 

RV of 22%). The representative value is the value most likely to be found 

for a particular soil property and is useful in computerized interpretive 

models. The RV can be determined by summarizing the values recorded 

on the individual pieces of point data. Tacit knowledge from individual 

soil mappers can be used to augment recorded point data measurements.

The physical, chemical, and morphological properties of the soils 

included in the aggregated data generally are most or all of those that are 

included in the point data. They should include any properties that are 

used to generate interpretive ratings.

Values for many physical and chemical soil properties of a particular 

soil map unit or map unit component commonly vary from one topographic 

position to another, or from one geographic location to another, within a 

particular map unit or even a single delineation of a map unit. Properties 

can also vary from one time of the year to another, from year to year, and 

from one land use and/or management system to another (see chapter 9 

for a discussion of dynamic soil properties). The database must have the 

capability to record this variability.

Aggregated data may represent map units that cover a particular 

geographic area at different map scales, for example, 1:12,000 or 

1:24,000 and also 1:100,000 or 1:250,000. The differences in scale may 

represent a “detailed” soil map of the area and a “generalized” soil map of 

the same area. Map unit design and the respective map unit components 

will generally differ between the larger (e.g., 1:24,000) and smaller (e.g., 

1:250,000) map scales. Types of soil map units and map unit design are 

described in more detail in chapter 4.

The U.S. National Cooperative Soil Survey and NRCS routinely 

produce and maintain soil data and map products at a variety of map 

scales. Figure 7-2 illustrates the hierarchical relationship between these 

aggregated data products and the original point data. The two primary 

soil survey products are SSURGO (Soil Survey Geographic Database) 

and STATSGO (U.S. General Soil Map).

Also included in the aggregated data are the various interpretive 

ratings for each soil map unit and each map unit component. Some ratings 

are applicable to the map unit as a whole (e.g., prime farmland rating), 

while others are applicable to the individual map unit components (e.g., 

limitations for building site development).

In order for soil survey data to be delivered to end users, aggregated 

data are commonly stored in a relational database. The database must 

be designed to store data for delivery and to support the various soil 

interpretations that are needed. Determining what will be delivered to users 
Soil Survey Manual 413

Figure 7-2

Conceptual model showing the relationships and degree of generalization of data 

between different map scales and products. (See chapter 4 for a discussion of orders 

of mapping.)
414 Chapter 7

at the end of the soil survey project (such as which chemical, physical, 

and morphological soil properties and which landscape relationships) 

helps in determining what data needs to be collected as point data.

Spatial Data

Spatial data is a major portion of the data collected or developed 

during a soil survey. It includes the geographic coordinates (e.g., latitude 

and longitude) that define the boundary of each map unit polygon on 

the soil map, whether it is in vector or raster format. It also includes the 

geographic coordinates for each point on the landscape where point data 

were collected. Boundaries of various political and physiographic areas 

may also be included as ancillary data layers. Other ancillary data layers, 

such as vegetative cover, digital elevation model (DEM) data, aerial 

photography, land use, and geology, are commonly used in a geographic 

information system (GIS) when conducting a soil survey. Derivative data 

layers (those developed from other data layers), such as wetness index, 

slope, and aspect, are also commonly used. Various soil property and 

interpretive maps can be developed using a GIS. A detailed discussion of 

digital soil mapping is provided in chapter 5. The appropriate scale and 

level of resolution or detail are important considerations when choosing 

which data layers to use.

The design of databases to house soil survey data must include a 

mechanism to link each individual map unit polygon on the soil map 

with the appropriate set of aggregated data describing the characteristics 

of the map unit represented by the polygon. The map unit symbol on the 

soil map is commonly used for this purpose.

To ensure that resulting spatial data are consistent and practicable 

to end users, standards for spatial data layers must be developed and/or 

adopted just as they are for collecting soil property data in the field. This 

includes the digitizing of soil maps. Establishing standards is especially 

important for large soil survey projects, which involve many soil survey 

parties. In order to get a consistent data set, the various soil survey parties 

must use standardized methods and techniques.

Because spatial data sets tend to be very large, adequate storage 

space must be considered when developing a computer system to 

manage soil survey data. In the U.S. soil survey database, the spatial data 

layer for the detailed soil maps occupies approximately one-third of the 

whole database. Another third is occupied by the associated aggregated 

soil attribute data, and another third by the included generated soil 

interpretation ratings. Additional storage space must be available for 

other data layers used in conducting the soil survey.
Soil Survey Manual 415

Soil Information Systems

As described earlier, a soil information system not only includes the 

actual soil survey data and information but also the various methods, 

computer applications, and processes used to collect, manage, store, 

and disseminate the data to end users. A variety of tools are available 

for electronically collecting soil data in the field. Data recorders can 

be connected to monitoring equipment to measure and record soil 

temperature and soil moisture at regular time intervals over an extended 

period of time. The data can then be imported into a permanent database. 

Handheld, tablet, and laptop computers can be programmed to 

display a variety of field forms. Data can be manually entered into 

digital memory in the field and later uploaded to a central soil database. 

Analytical instruments in the laboratory can be connected to a computer 

to automate the recording of analytical test results. Global positioning 

systems (GPS) and digital cameras can be connected to these computers 

so that geographic coordinate data and photographs can be linked to 

other data being collected. Computers with GIS software allow the user 

to draw the soil map electronically in the field instead of manually on a 

hard copy. Capturing data electronically eliminates the need to later key 

the data values into the computer. This greatly increases work efficiency 

and eliminates a possible source of data entry error.

Techniques are being developed to allow the field soil scientist to 

generate a preliminary soil map using computer algorithms or programs 

that replicate the interaction of the five soil-forming factors, i.e., 

topography, climate, parent material, living organisms (especially native 

vegetation), and time. These algorithms use logic developed by soil 

scientists knowledgeable of the area being surveyed. This approach to 

developing the soil map, referred to as digital soil mapping, is discussed 

in detail in chapter 5. 

Computer applications are very useful in managing, editing, and 

delivering soil survey data collected in the field. They provide the 

capability to more readily update the soil maps and associated data and 

to keep the information current. Thus, they allow quicker and easier 

regeneration of end products and publication of the updated information.

As with any computerized system, the system itself needs to be kept 

up-to-date. New versions of software will need to be installed. Computer 

hardware eventually will need to be repaired or replaced. People will 

need to be trained on how to use the system. Issues and questions will 

occur on a day-to-day basis as problems arise with the system. They will 

require personnel with information technology skills as well as those 

with soil business skills. 
416 Chapter 7

Uses of Soil Survey Information

The demand and use of soil data and information is growing at a rapid 

pace. Figure 7-3 illustrates the increased number of users of NRCS’s 

Web Soil Survey application. Web Soil Survey (Soil Survey Staff, 2016) 

was implemented in 2005 and is the agency’s primary public distribution 

tool for official soil survey data and information. The variety of users 

is also expanding. Soil surveys most commonly are made for areas that 

have more than one kind of important land use and for users who have 

varied interests and needs. These needs may be few and noncomplex, as 

in areas of extensive land use where change is not expected, or they may 

be many and complex, as in areas of intensive land use where changes 

are expected.

Figure 7-3

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

March

2006

March

2007

March

2008

March

2009

March

2010

March

2011

March

2012

March

2013

March

2014

March

2015

March

2016

WSS Average Visits per Day

An illustration of the increased number of users of NRCS’s Web Soil Survey (WSS) 

application.

Predictions for uses of soils other than farming, grazing, wildlife 

habitat, and forestry have tended to concentrate on limitations of soils for 

the intended uses. Where investment per unit of area is high, modifying 

the soil to improve its suitability for the intended use may be economically 

feasible. Soil scientists work with engineers and others to develop ways 

of improving soils for specific uses. Such predictions are increasingly 

important in areas where the demand on soil resources is high.

The information assembled in a soil survey may be used to predict or 

estimate the potentials and limitations of soils for many specific uses. The 
Soil Survey Manual 417

information must be interpreted in forms that can be used by professional 

planners and others. A soil survey represents only part of the information 

that is used to make land management plans, but it is an important part. 

Chapter 8 discusses soil interpretations in detail.

The predictions of soil surveys serve as a basis for decisions about 

land use and management for both small tracts and for regions consisting 

of several million acres. They must be evaluated along with economic, 

social, and environmental considerations before recommendations for 

land use and management can be valid.

Soil surveys are used to appraise potentials and limitations of soils 

in local areas having a common administrative structure. Planning at this 

level is sometimes called community planning. It applies to community 

units (villages, towns, townships, counties, parishes, etc.) and to trade 

areas that include more than one local political unit.

Soil surveys also may be used to evaluate soil resources in multi-county 

or multi-State areas that have problems that cannot be resolved by local 

political units. Regional planning involves land use in broad perspective 

and appraises large areas. It is done in less detail than community 

planning. Soil surveys and their interpretations for regional planning 

are correspondingly less detailed and less specific. Soil maps and their 

interpretations for regional planning must provide graphic presentations of 

the predominant kinds of soil of corresponding large areas.

Soil surveys provide basic information about soil resources needed 

for planning development of new lands or conversion of land to new 

uses. This information is important in planning specific land uses and the 

practices needed to obtain desired results. For example, if recreational 

use is being considered, a soil survey can indicate the limitations and 

potential of the soil(s) in the area of interest for recreational uses, such 

as playgrounds, paths and trails, or off-road vehicle use. It can help a 

landscape architect properly design the area. A contractor can use the 

soil survey in planning, grading, and implementing an erosion-control 

program during construction. A horticulturist can use it in selecting 

suitable vegetation for landscaping.

Soil surveys provide a basis for decisions about the kind and intensity 

of land management, including those operations that must be combined 

for satisfactory soil performance. For example, soil survey information 

is useful in planning, designing, and implementing an irrigation system 

for a farm. Information regarding the kind of soil(s) and associated 

characteristics helps in determining the length of run, water application 

rate, soil amendment needs, leaching requirements, general drainage 

requirements, and field practices for maintaining optimum soil conditions 

for plant growth.
418 Chapter 7

Soil surveys are also useful in locating possible sources of sand, 

gravel, or topsoil. They are an important component of technology 

transfer from agricultural research fields and plots to other areas with 

similar soils. Knowledge about the use and management of soils has been 

spread by applying experience from one location to other areas with the 

same or similar soils and related conditions.

The hazards of nutritional deficiencies for plants, and even animals, 

can be predicted from soil maps if the relationships of deficiencies to 

individual soils are established. In recent years, important relationships 

have been discovered between many soils and their deficiencies of 

copper, boron, manganese, molybdenum, iron, cobalt, chromium, 

selenium, and zinc. The relationships between soils and deficiencies 

of phosphorus, potassium, nitrogen, magnesium, and sulfur are widely 

known. Relationships of soils to some toxic chemical elements have 

also been established. However, many soils have not been characterized 

for these conditions (especially for trace elements) and more research is 

needed.

Soil surveys commonly provide essential data and information for 

the compilation of general soil maps. Many soil surveys are done for 

purposes that require relatively intense field investigation and map scales 

of about 1:12,000 to 1:24,000. However, a smaller scale soil map with 

more broadly defined units may be better for developing land use plans 

for large areas. General soil map scales range from about 1:100,000 

to 1:1,000,000 and provide an overview of the location and extent of 

dominant soils in a large area. A general soil map can be made by grouping 

units of the large-scale soil maps and generalizing the map detail. The 

resulting map units may be more useful for the intended use. The amount 

of information that can be given about the units on a general soil map—

and, therefore, the number of feasible interpretations—depends on the 

degree of generalization of the map units, which is determined by the 

map scale. Computer applications such as GIS greatly facilitate the 

summarization and generalization of detailed soil survey data during the 

development of the smaller scale soil map units.

Small-scale soil maps can provide a basis for comparison of broadly 

defined capabilities and limitations that relate to the soil on regional, 

national, and even worldwide scales. International cooperation among 

soil scientists has accomplished much in relating the different soil 

classification systems of various countries to one another using smallscale maps. This permits the findings of research on soils of one country 

to be extended to similar kinds of soil elsewhere. Soil Taxonomy (1975 

and 1999) and the Soil Survey Manual (1951 and 1993) have guided soil 

scientists worldwide for many years. Many have contributed ideas and 
Soil Survey Manual 419

data to the soil survey system. As a result, the uses of soil survey data 

have been extended far beyond the boundaries of the countries where the 

data were originally obtained.

Dissemination of Soil Survey Information

Mechanisms are needed to deliver completed soil survey information 

to end users. Depending on the needs of the users, a variety of types, 

content, and formats of soil survey products may be needed. Each type 

of product may require a somewhat different mechanism for delivery.

Some users may want the raw data collected during the course of 

the soil survey project delivered to them in digital format. Others may 

want hard-copy printed soil maps along with the associated descriptive 

information of each soil map unit and the respective map unit components 

and interpretations. Some users may need access to the most up-to-date 

information available for the area and want to see it in an online computer 

application that allows them to zoom into a particular tract of land. They 

may not need or care about the data for the whole soil survey area. They 

may only be interested in soil survey data and interpretations that pertain 

to a particular land use. Other users may only be interested in soils data 

for larger areas for regional planning.

Some users prefer to have direct online access to soil data so that 

they can integrate this data with other data systems and applications on 

their local computer. Web services are tools that have been developed 

to accommodate such access. With these services, the user can connect 

to the database in a read-only mode and then query the spatial and 

tabular data for the geographic area of interest. These services also allow 

the user to have access to the most up-to-date data available without 

having to acquire and maintain the data on their local system. With the 

increased use of computers and geographic information systems and 

other applications, this method of disseminating soil survey data and 

information is becoming more widespread and popular.

Requests for soil survey data and information are commonly received 

while the survey is still in progress. Decisions must be made as to how 

to handle such requests and what data and/or information is suitable to 

be released at the time of the request. Any information provided should 

be marked as “preliminary” and “subject to change” until it has been 

fully reviewed and certified. Some requests may include the need for 

specialized interpretations of the data, and a mechanism should be 

available to provide those interpretations if at all possible.

Soil survey data and information, including both tabular and 

spatial data, can be delivered to end users in various formats. Tabular 
420 Chapter 7

data include the map unit and map unit component descriptions; their 

physical, chemical, and morphological data; and interpretations of each 

soil for a variety of uses. Spatial data include the soil map unit boundaries 

and location for any point data that were collected within the survey 

area. Photographs are commonly included to illustrate the different soil 

landscapes within the survey area and to show significant features of 

the different soils. Narrative text is also included to convey information 

to the end users that may not be represented in the tabular data and to 

describe relationships between the different soils of the area.

Tabular data can be delivered to users as raw data in electronic 

database format, either online or in a standalone database file that can 

be loaded onto their local computers. The data can also be presented as 

formatted reports of various content. These reports can be delivered as 

electronic files for viewing or as hard-copy printouts. Tabular data can 

also be presented as thematic maps that incorporate the spatial data for 

the map unit delineations (see appendix 4 for examples). Depending on 

the scale of mapping and the map unit design, individual delineations 

may be represented on the map as polygons, lines, or points. 

Thematic maps display a rating for each map unit delineation. If 

a particular soil map unit has multiple map unit components and the 

components may have different interpretive ratings for a particular 

interpretation, ratings need to be aggregated so that a single overall 

rating for the map unit can be delivered. This aggregated rating can then 

be assigned to the applicable delineations for that map unit. Various 

aggregation methods may be used, such as dominant component and 

dominant condition. For example, a map might show the distribution of a 

soil property, such as surface layer pH or surface layer clay content. The 

various interpretations, such as suitability or limitations of each soil map 

unit for septic tank absorption fields, can also be presented in formatted 

reports or as thematic maps.

Soil maps can be presented as digital files for use on a local computer. 

The digital files can be the raw data representing the soil map unit 

boundaries or contain formatted soil maps that can be viewed on the local 

computer or printed locally. The map unit boundaries can be presented 

in vector or raster format. In vector format, the map unit boundaries are 

defined by a series of x y coordinates (such as latitude and longitude) 

that, once plotted, replicate the shape of the original map unit boundaries 

drawn on the map. In raster format, the soil map is divided into a gridded 

format in which each grid cell is at a resolution that best represents the 

shape of the original soil map unit polygons. Popular resolutions include 

10- and 30-meter, meaning that each grid cell represents an area 10 by 

10 or 30 by 30 meters on the Earth’s surface. Corners of each grid cell 
Soil Survey Manual 421

are defined by standard latitude and longitude or UTM coordinates. Both 

vector and raster formats have advantages and disadvantages. Soil maps 

can also be delivered as printed hard copies.

During the course of the soil survey project, special studies of selected 

soils within the survey area or region may be conducted. These studies 

may involve detailed laboratory examination of the physical, chemical, 

and mineralogical composition of the soils. Other studies may focus on 

the genesis of the soils or the geomorphology of the area. Results of 

such studies are used to help populate the soil database for the survey 

area and are commonly published in special soil investigative reports and 

scientific papers in technical journals. Papers discussing the studies are 

commonly presented at meetings of professional scientific organizations.

Whatever system is developed to collect, store, manage, and deliver 

soil survey data and information, the variability of formats and content of 

information disseminated must be considered. Demands for soil survey 

information are changing and are expected to continue to change at an 

even faster pace. The system will likely need to be changed to meet future 

needs and demands. The idea of “one size fits all” or “one product meets 

all user needs” is no longer appropriate. Any system that is developed 

to deliver soil survey information must have built-in flexibility so that it 

can be updated and modified to meet the ever changing needs of users. 

However, it is important to remember that the more flexibility one builds 

into the delivery system the more maintenance and upkeep cost will be 

required in the years to come.

History of Soil Data Management in the U.S.

The development and evolution of a national system to collect, store, 

manage, and disseminate soil survey data and information for the U.S. 

National Cooperative Soil Survey (NCSS) began in the late 1960s and 

early 1970s and included several iterations. As with other information 

technology, the pace of development and functional capacity has steadily 

accelerated since the mid-1990s. 

The First Generation

The USDA Soil Conservation Service (SCS), renamed the Natural 

Resources Conservation Service (NRCS) in 1994, first established a 

national soil database in the early 1970s through a cooperative agreement 

with the Statistical Laboratory at Iowa State University (ISU) (Fortner and 

Price, 2012). ISU was chosen because of its long history of cooperative 
422 Chapter 7

work with the SCS, dating back to the 1940s. Programming work for a 

soil database began in 1972 with automation of the soil interpretations 

record (SIR), or SOI-5 form, which was used primarily as an input form 

to generate tables on engineering uses of soils for published soil survey 

reports. The SOI-5 form was first developed in the late 1960s. At least 

one SIR was developed for each soil series recognized in the soil survey 

of the United States. Some soil series had more than on SIR, depending 

on how many phases of the series were recognized and mapped. 

Computer programs were developed to store, check, and print the 

data. The soil interpretation record for the Cecil soil series (NC0018) 

was the first one stored on the ISU mainframe in 1973. In 1974, the 

generation of manuscript tables of soil properties for inclusion in soil 

survey reports was introduced. Initially, all data processing was done at 

ISU and a printed copy of the tables was sent through the mail. The SOI5 forms, along with the SOI-6 forms, which were used to enter specific 

map unit information for the soil surveys, were mailed from SCS offices 

to ISU for processing. Printed copies of revised records and generated 

tables were mailed back to the SCS office requesting the tables. This 

automated table generation system replaced the very tedious, timeconsuming manual process of creating tables for the published reports. 

With the availability of this useful product came a much greater 

interest in storing data in the computer system. In 1977, the system 

gained the capability to automatically generate soil interpretations for 

26 selected (mostly engineering) uses from the soil data stored in the 

database using programmed criteria. These interpretive ratings were 

stored in the database and printed on the hard-copy SOI-5 forms. After 

1977, other enhancements were developed, including the addition of the 

Official Soil Series Description (OSD) and Soil Series Classification 

(SC) databases.

Computerization in SCS offices for processing soil survey data 

began in 1977 with Linolex word-processing equipment in SCS National 

Technical Center offices. This equipment was used to prepare manuscript 

tables received on magnetic tape from ISU for final publication. Remote 

access to ISU from SCS, in both State and regional offices, began in the 

early 1980s with Harris Remote Job Entry equipment. Communication 

was through 4800-baud dial-up communication ports. It was a time of 

significant change as batch software had to be redesigned for remote 

usage and data entry. Processing and printing of manuscripts shifted 

from ISU to SCS offices.

The SIR database remained operational until 1996, when it 

was retired after the release of the new National Soil Information 
Soil Survey Manual 423

System (NASIS) software and database. About 35,000 SIRs were 

developed during the 24 years that the SIR database was active.

The Second Generation

Work on the second generation of the national soil database began 

in 1978, when SCS developed a computer program to rate soils for 

prime farmland and other important farmland classes and create maps 

for the Colorado Important Farmlands project. This project required the 

rating of about 4,500 soil map units in Colorado. It used national criteria 

for prime farmland and State criteria for farmland of State importance 

and unique farmland. The most difficult problem was making ratings 

consistent across soil survey areas. The program evaluated 10 soil 

characteristics and was fairly accurate in its ratings. However, a large 

database was required to make the ratings and the effort required to 

develop the database made the project unfeasible. The need for a large 

database, which would also be readily accessible and easy to manipulate, 

resulted in the development of concepts for the second generation of soil 

information management.

These concepts were first documented in 1980 in the first technical 

report for the Colorado Soil Resource Information System (SRIS). 

SRIS demonstrated the feasibility of integrating several natural 

resource databases into a common, easy-to-use data environment. 

SRIS included: (1) a soil map unit component database, (2) a soil 

interpretation database, (3) a pedon characterization database, (4) 

a climatology database, (5) a plant database, (6) a soil management 

component, and (7) a schema for the data and description of the system. 

SRIS was the first effort to manage soil data using a new technology 

called database management systems (DBMS). The new information 

system allowed questions relating to more than one natural resource to 

be answered. It facilitated easy access to soil information and allowed 

the data to be managed independently of the application software that 

accessed it, while the SIR database required a computer program to be 

written for each unique request. In 1982, the SRIS soil database was 

implemented in Colorado.

As an outgrowth of the SRIS effort, SCS established the software 

development staff at Fort Collins, Colorado, in 1985. The mission of 

this staff was to develop computer software to assist the SCS field 

offices. In 1987, this effort resulted in the deployment of the Computer 

Assisted Management and Planning System (CAMPS) field office 

software and the State Soil Survey Database (SSSD). SSSD, which was 
424 Chapter 7

a UNIX-based application and used Prelude RDBMS software, was 

the culmination of the SRIS effort and was populated using map unit 

specific information and querying the SIR database. The resulting soil 

survey data collectively were called the Map Unit Interpretation Record 

(MUIR) database.

With the release of SSSD in 1987, SCS State offices were equipped 

with UNIX computers. The SSSD software allowed the State offices 

to manage their portion of the soil survey databases, which were 

downloaded from Iowa State University via telecommunications. 

The primary function of the first release of SSSD was to review the 

included soil data, make necessary edits, and provide a download of 

the MUIR database to CAMPS. The first release of SSSD provided the 

ability to develop reports through standard database queries and manage 

nontechnical soil descriptions. With this software release also came 

the recognition that a soil scientist position (soil dataset manager) was 

needed at each SCS State office to manage the soil information system.

Using SSSD, the SCS State offices could edit the soil map unit 

property and interpretation (MUIR) data at ISU and thus more accurately 

represent local conditions. The offices returned a copy of the edited 

data to ISU. This editing capability provided for a national collection 

of MUIR data in 1993. SSSD releases in 1988 through 1993 added 

additional capabilities. In 1988, the Pedon Description Program, version 

1.0, and the Official Soil Series management and soil reports modules 

were released. 

In 1989, the interface between the Soil Survey Geographic Database 

(SSURGO) and the Geographic Resource Analysis Support System 

(GRASS) was released. In 1989, a UNIX mail system called SoilNet 

and an automated version of the SOILS-6 form, which was used to 

record map unit data and facilitate the downloading and managing of 

MUIR data from ISU, were released. In 1991, the Soil Survey Schedule 

module was released. This module provided management, scheduling, 

and record-keeping software for SCS State and national offices to use 

in soil survey efforts. In 1993, the Hydric Soils, Range Site, and MUIR 

incremental update modules were released.

Although table generation remained its primary purpose, the MUIR 

database was soon used for more than developing soil interpretation 

tables for reports. SCS began to use the database to answer questions on 

a wide range of soil-related issues across the United States, for example, 

the extent of salt-affected soils, soil loss tolerance and erosion potential 

for determination of highly erodible land, and identification of hydric 

soils (wetlands). The uses of the soil database continued to expand and 

change until it became apparent in 1988 that SSSD and MUIR could 
Soil Survey Manual 425

not meet the changing needs. New information systems technology was 

available that could advance the use of soil survey information.

The SIR and MUIR soil database system was remarkable in that it 

was able to evolve in many ways over time but still kept its basic system 

design for about 25 years, until it was retired in 1996. At that time, the 

MUIR database contained data from about 2,900 soil survey areas and 

included approximately 250,000 soil map units. Implementation of the 

replacement system, the National Soil Information System (NASIS), 

began in 1994. Before the SSSD system was retired, the soil information 

in the MUIR database was converted to the new NASIS database.

The Third Generation

Development of NASIS began with the analysis and documentation 

of the business of soil survey from beginning to end. Teams from various 

levels in the U.S. National Cooperative Soil Survey (NCSS) were 

established to complete the requirements analysis. Using structured 

systems analysis, these teams documented requirements, which were 

passed on to contract software programmers. This analysis documented 

the important shift of the NCSS from producing static, printed soil survey 

reports to providing a dynamic database of soil information that could 

meet a wide range of needs and the ever growing demand for soil survey 

data and information.

A field data collection system was needed to ensure the integrity 

and completeness of the data, including geographic coordinates. The 

system was designed to provide users accurate and complete soil survey 

information based on what was observed during the soil survey process. 

Implicit in this idea was the ability to describe accurately the variability 

of soils and their properties as they occur on the landscape. This new 

system had to provide for a continuous update of the database as new 

information was gathered, so that one version of these data would be 

available to users at the field, State, and national levels.

NASIS had to provide a means for a variety of scientists to develop 

interpretation criteria and generate soil interpretations based on local, 

State, or national requirements. For example, at the local level there 

might be a need for an interpretation of soil suitability for animal 

waste disposal and at the national level there may be a need for a 

soil productivity index. To ensure consistency, these interpretations 

must be applied to only one nationally consistent version of the data. 

The system had to provide for effective and efficient data delivery, 

including easy access by both internal and external (non-NCSS) users. 

This information needed to be delivered with a common data structure, 
426 Chapter 7

data dictionary definitions, and appropriate metadata so that users could 

understand the information and apply it appropriately.

NASIS System Objectives

Many weeks of analysis (discussion) and numerous follow-up 

meetings identified the following specific system objectives (Soil Survey 

Staff, 1991):

• The placement of automated tools in the hands of field office 

staff

• One-time data entry, so that data could be retrieved by multiple 

software modules in various computer programs

• A simple means of entering data in the same format as that used 

during data collection

• Validations to ensure proper entry of data and algorithms to 

provide default values

• Automated procedures for correlation and quality assurance

• Flexibility of the system to adapt to changes in procedure and 

standards and to new data needs and policies

• Capability to aggregate large-scale digital soil maps to smaller 

scales based on user-defined criteria

• Data manipulation and retrieval options for all databases and 

software modules that include modeling capability

• The ability to use single property values or representative values, 

in addition to ranges, in models

• Capability to indicate confidence limits and the reliability of map 

unit data

• Continuous update of national, State, and field office soil survey 

databases

• Access to State and national databases to enter or edit data 

managed at appropriate office level

• Permanent storage of all soil survey documentation

• Capability to transfer data files between various kinds of 

equipment

• Two-way linkages to other natural resource databases

• Software modules that are interactive, menu driven, and user 

friendly

• Training on how to use the new system

NASIS Software Development and Implementation

As with the SSSD software, the initial releases of the NASIS 

software were in successive yearly versions. New or updated functions 

and capabilities were added with each release.
Soil Survey Manual 427

• Version 1.0, released in 1994, was implemented in each SCS 

State office. Each State held and managed the data for their 

respective soil survey areas. NASIS 1.0 was developed in the 

C+ programming language using the X Window system, a 

UNIX-based graphics window system. Similar to the Microsoft 

Windows application that comes on many personal computers, 

the X Window system is a graphical user interface (GUI). 

INFORMIX was selected as the NASIS database management 

software (DBMS) largely because of its security features. 

This proprietary design enabled the construction of a system 

that prevents most accidental or intentional corruption of data. 

NASIS allows different data records in the database to be owned 

by different individual users or groups of users, so that only 

qualified scientists can edit or create data. The owner of an object 

has the authority to change data as needed. Individual or group 

ownership can be established as needed.

Version 1.0 provided validation and conversion of 

MUIR data to the NASIS database structure; a security 

system and controls; an operational data dictionary; editors 

for areas, legends, and data map units; and online help. 

Individual NASIS users accessed the system using a Webbrowser-based interface that connected to their respective 

State database for data input and editing.

• Version 2.0, released in 1995, provided Cut, Copy, and Paste 

functions for data objects, a query editor and manager, global 

assign functions, report generation, and an enhanced online help 

system. 

• Version 3.0, released in 1996, provided calculation and 

validation routines for data and the ability to create criteria for 

interpretations and generate interpretations. This was a major 

step that allowed for the creation of specialized interpretive 

criteria and the evaluation of each map unit component against 

those criteria.

• Version 3.1, released in 1997, provided for the replacement 

of the national MUIR data with NASIS data and consolidated 

NASIS databases from individual State offices to the original 17 

MLRA soil survey regional offices. It provided downloads to the 

NRCS field office computing system (FOCS) and downloads of 

SSURGO-format datasets. Releases of versions 1.0 through 3.1 

primarily addressed the development and management of map 

unit data.
428 Chapter 7

• Version 4.0, released in 1998, provided data tables for storing 

site and pedon description data and incorporated capabilities 

for input of and access to pedon descriptions and soil site 

information. It also replicated storage of national map unit data 

via the Internet at ISU and data sharing via the Internet. 

• Version 5.0, released in 2001, further consolidated the NASIS 

database to a central server environment at the NRCS Information 

Technology Center in Fort Collins, Colorado. Data storage at 

ISU was discontinued. 

• Version 5.2, released in 2003, included the capability to export 

datasets to the Soil Data Warehouse for each soil survey area.

• Also in 2003, Version 2.0 of the Soil Survey Geographic 

(SSURGO) data model was adopted and implemented for 

the distribution of official soil survey tabular attribute data. 

Concurrently with this release, the Soil Data Warehouse and Soil 

Data Mart were implemented (see below).

• Beginning in 2004, development of a new generation of NASIS 

began. As a result, NASIS 6.0 was released in 2010. This version 

introduced a client-server-based environment where the user 

interacted with the national soil database on the central server 

using a version of the NASIS application on their local personal 

computer. It is a Microsoft Windows-based system using a .NET 

operating system and SQL Server DBMS.

NASIS 6.0 introduced the concept of managing soil 

survey data by projects rather than the traditional soil 

survey areas (typically county-based legends). This concept 

promoted designing map units on the basis of their natural 

geographic occurrence rather than limiting their spatial extent 

to geopolitical boundaries. A process of data updating and 

recorrelation was begun to ensure a seamless join of spatial 

and attribute data between soil survey areas. As a result, soil 

properties, qualities, and interpretations of map units and 

their components extend across geopolitical boundaries to 

their full natural extent.

• Periodic minor releases of NASIS continued to add new 

functionalities to the system and refine the data model as needs 

changed. 

• In 2014, Version 7.0 of the NASIS database was released. It 

included the addition of data tables to house vegetation-related 

point data collected as part of the Ecological Site Inventory. These 

data will be used to develop Ecological Site Descriptions of the 
Soil Survey Manual 429

U.S. The data model allows pedon descriptions and laboratory 

analysis data from a given location to be related to vegetation 

data from the same location. Existing vegetation inventory data 

from other existing databases will be converted and imported 

into the new NASIS tables.

• In 2016, Version 7.0 of the NASIS application was released. It 

gave NASIS users the ability to create user-specific forms, which 

they could use (instead of the traditional NASIS edit screens) to 

create, view, and edit data.

Digitization of Soil Survey Maps

Interest in digitizing NCSS soil maps began with the introduction 

of the Map Information Assembly and Display System (MIADS) to 

SCS in 1971. MIADS was a cell-based method of digitizing and was 

primarily used for creating interpretive data. Oklahoma was one of the 

States that digitized most or all of their soil surveys using this system. 

Efforts to find an efficient, feasible, and consistent method to digitize 

soil maps using the line-segment method continued. Various methods 

were tested. In 1990, standard policies and procedures for digitizing new 

and updated soil surveys, issued as “National Instruction No. 170-303 

CGI—Technical Specifications for Digitizing Detailed Soil Maps,” were 

adopted by the SCS Soil Survey Division. The intent of these standards 

was to establish a set of policies and procedures for everyone to use and 

so ensure products have consistent quality. Getting soil maps digitized 

was a slow progress and involved a variety of in-house personnel as well 

as contractors.

NRCS started the SSURGO Soil Survey Digitizing Initiative in 1995 

with a special appropriation of funds. Although some soil surveys had 

been digitized as early as 1975, the SSURGO initiative was the first 

concerted effort to digitize all of the soil surveys in the U.S. It began 

a massive 12-year project to convert hard-copy soil maps to SSURGO 

and lasted through 2007. During this period, many soil surveys were 

updated as they were digitized. Digitizing centers were established to do 

the actual digitizing work or to conduct quality reviews of work done by 

others. 

Beginning in the mid- to late-1990s, digitizing soil maps became 

part of the actual soil survey project work. Digital maps are one of the 

initial products of new or updated soil surveys. A soil survey project is 

not considered complete until the digital maps are available and meet 

established standards.
430 Chapter 7

Soil Data Warehouse and Soil Data Mart

Early business analysis for a national soil information system 

identified the need for a single point of delivery of official soil survey 

data and information and the ability to archive versions of official 

data. (The NASIS database and application are intended primarily for 

internal use in developing and managing soil survey data and not for 

public access or delivery of data.) To meet this need, the Soil Data 

Warehouse (SDW) and Soil Data Mart (SDM) were deployed in 2003. 

By that time, significant progress was being made in digitizing soil 

survey maps. 

The SDW is designed to hold all versions of official soil survey 

data (both SSURGO2 and STATSGO) produced since 2003, including 

not only tabular attribute data and digital spatial data but also metadata 

files that comply with the standards of the Federal Geographic Data 

Committee (FGDC). The SDM database contains only the most current 

version of official data and initially served as the data-distribution site. 

It provided a public access point for the data and allowed the user either 

to download digital SSURGO datasets in a standard format for use in a 

local geographic information system (GIS) or to run standard soil survey 

reports on selected datasets. In 2013, the data distribution function of the 

SDM was migrated to the Web Soil Survey (see below).

SSURGO Access Database Template

When data were downloaded from the Soil Data Mart, the attribute 

data tables were in a series of unrelated text files. For the data to be 

used, they first had to be loaded into a relational database format of the 

user’s choosing. A database template in Microsoft Access format was 

developed for this purpose. The template includes macros for loading the 

data as well as standard queries and reports for viewing the data. It was 

included with each data download.

Soil Data Viewer

Soil Data Viewer (SDV) is an application developed as a plug-in 

extension of ESRI ArcMap for viewing digital soil maps downloaded 

from the Soil Data Mart and later from Web Soil Survey. It requires the 

SSURGO Access Database Template (described above) for accessing 

the attribute data. It was developed to help shield the user from some 

of the complexity of the attribute data structure. SDV includes a series 

of rules for aggregating soil properties and interpretations of individual 
Soil Survey Manual 431

map unit components to a single value for the respective map units for 

display in the GIS-generated thematic maps. This tool is available to 

the public. 

Web Soil Survey

As the digitizing of soil survey maps progressed and the Soil 

Data Mart became more fully populated with data, users began to ask 

questions (e.g., Why could they not view the soil maps from the SDM 

online? Why did they need to download the data?). Many users did 

not have the equipment or expertise to work with the data themselves. 

To address this issue, the Web Soil Survey (WSS) was developed and 

first deployed in August 2005. It provides a publicly accessible online 

interface to the national collection of SSURGO datasets in the SDM 

database. In WSS, the user must first delineate the area of interest 

(AOI) for which they want to obtain soil survey data and information. 

The AOI may be an individual farm or ranch, an individual farm field, 

a watershed drainage area, or a whole soil survey area. It is also not 

limited to part of a single soil survey area but can span multiple survey 

areas. Users can define their AOI by using graphical tools that are part 

of the WSS interface, or they can upload a boundary developed in their 

local GIS.

After delineating the AOI, the WSS user can display the soil map 

for the selected area, generate interpretive or thematic maps for a wide 

variety of uses or selected soil properties, print individual maps or 

accumulate them into a composite report, or download the SSURGO 

data for the selected area. Data related to thematic maps are also included 

with SSURGO data downloads so that the user can generate similar maps 

using their local GIS software.

WSS merges the datasets and displays data and maps in a single 

layer. It uses the same rule set that Soil Data Viewer uses for aggregating 

data for display at the map unit level. It also provides the capability to 

download the underlying SSURGO dataset clipped to the AOI boundary 

for use in a local GIS. 

In 2013, Version 3.0 of WSS was released. With this release the 

process of downloading official soil survey data, both SSURGO2 and 

STATSGO, was transferred from the Soil Data Mart to Web Soil Survey. 

SSURGO2 datasets are available for whole soil survey areas for the 

United States. STATSGO data are available as individual State datasets 

or for the whole U.S. As was the case with SDM, each data download 

includes a copy of the SSURGO Access Database Template. 
432 Chapter 7

References

Fortner, J.R., and A.B. Price. 2012. United States soil survey databases. 

In P.M. Huang, Y. Li, and M.E. Sumner (eds.) Handbook of soil 

sciences, 2nd edition, CRC Press, Boca Raton, FL.

Schoeneberger, P.J., D.A. Wysocki, and E.C. Benham (editors). 2012. 

Field book for describing and sampling soils, version 3.0. USDA 

Natural Resources Conservation Service, National Soil Survey 

Center, Lincoln, NE. Available at http://www.nrcs.usda.gov/wps/

portal/nrcs/detail/soils/research/guide/?cid=nrcs142p2_054184. 

[Accessed 27 September 2016]

Soil Survey Staff. 1991. National Soil Information System—soil interpretation and information dissemination subsystem. Draft requirements 

statement. USDA Natural Resources Conservation Service, National 

Soil Survey Center, Lincoln, NE.

Soil Survey Staff. 2016. Web Soil Survey. USDA Natural Resources 

Conservation Service. http://websoilsurvey.nrcs.usda.gov/ [Accessed 

10 October 2016]