Thomas P. D'Avello
DEVELOPING A SOIL SURVEY OF THE FUTURE
The traditional soil survey reports are the product of the most
comprehensive natural resource inventory in the world. The format
of the report has been static for many years. This media and format
can be cumbersome to use and information can be difficult to find.
The goal of a soil survey is to provide quality information for land use
planning and management. Any limitations regarding ease of use and
understanding hamper this goal. Advances in desk-top GIS technology
and meetings with users led us to development of a prototype soil
survey on a CD-ROM. ArcView2.1, Avenue and ArcView Publisher are
being used to create an interactive soil survey, SoilView, that users
can navigate with minimal training. This paper will present the
concepts, design and features of the prototype application.
BACKGROUND
The traditional soil survey reports developed through the United States
National Cooperative Soil Survey Program, are the product of the most
comprehensive natural resource inventory in the world. The format of
the report has been unchanged for the past 40 to 50 years consisting
of a bound document with three major sections:
This media and format can be cumbersome to use, requiring the user
to shift back and forth between a map(s) of interest and corresponding
non-spatial data In addition, many of the terms and concepts used in
the report are unfamiliar to many users (Valentine et al. 1981). The
goal of a soil survey report is to provide consistent, reliable information
on the pattern of occurrence and behavior of soils for multiple land uses
and management. Any limitations regarding ease of use and
understanding hamper this goal.
CURRENT STATUS
There is a soil survey for most of the 3,000 plus counties in the United
States. However, the scale, base map, and classification system used
varies from county to county. The current emphasis is to bring
consistency to the soil survey across political boundaries using the
knowledge gained from the past 100 years (Indorante et al. 1996).
All soil surveys will now be done using USGS digital orthophotographs at
1:12000 or 1:24000 scale as a base map, all text, tables and spatial data
will be in digital form and archived as ASCII text, delimited ASCII text and
DLG3 Optional file formats respectively. Availability of the digital data will
be through the Natural Resources Conservation Service (NRCS) National
Cartographic Center or State Office.
IS THIS ENOUGH ?
Even with the digital emphasis we were still concerned that we would
not be meeting the needs of most of our users. Formal and informal
meetings and user surveys confirmed our suspicion:
- Most users don't have $1,000 to $20,000 tied up in GIS software/hardware
- Those that do, don't always have a day or two to import/manipulate data
- Users would prefer to have a digital product that comes ready to use.
WHAT USERS WANT
Many people are familiar with and use CDROMS, multi-media educational
software, World Wide Web browsers etc. Once these products came on
the market, the thought of creating an interactive, multimedia soil survey
took hold. With funding from the NRCS National Soil Survey Center, we
started our journey towards creation of an interactive digital soil survey
with the development of a wish list of features that included:
- Run under Windows
- Pure database capability
- Have links between maps tables, and text
- Map manipulation via database manipulation
- Hyper-links for graphics and text
- View multiple map "sheets" as one image
- Photographic background
- Easy to Use.
A review of available software led us to ArcView2.1 and ArcView
Publisher as the products that met all of the user requirements.
SOILVIEW
Data Preparation
The desire was to include all of the data for a soil survey on one CD.
In order to accomplish this, some data manipulation was required, primarily
with the digital orthophoto quarter quads, whose size averages 50
megabytes each. The digital orthos were resampled from 1 meter to 5
meter resolution using the cubic convolution method, and trimmed at the
3.75' neatline, reducing their file size about 96%, while maintaining
reasonable spatial resolution. Tab delimited ASCII tables were extracted
from the NRCS map unit interpretation record (MUIR) tables, normalized
and converted to "dbf" files. The text data was converted into a
stand-alone hyper-media document, while soil coverages were converted
to shapefiles.
The Interface
Users of soil surveys want to determine information on the attributes of a
soil(s) or determine the spatial extent of a soil attribute(s), or both. In
gathering this information users most often start from a map and proceed
to a table or text, and occasionally employ the inverse of this method.
SoilView allows the user to pursue either route.
SoilView uses a customized project with fewer buttons/tools, unique menus
and several customized tools, with the goal of making the software as easy
to use as possible without limiting the essential functionality required to
utilize the survey. Our findings indicated that most users are not, nor ever
will be GIS gurus.
As part of the project start-up, all tables, text, and a predefined view of
the soil index map become available. Once a user opens the "County View"
view , they may select a particular soil map by using a tool created called
"Select-by-point", or "Select-by-rectangle" (Figure 1).
Figure 1. Soil survey index map.
Scale dependent display of the shapefiles for the quarter quad views is set
at 1:30,000 to reduce drawing time and clutter. An example of a view
showing the interface will give you an idea of what menus/buttons/tools
are available (Figure 2).
Figure 2. View of soil map.
The following close-up with the digital orthophoto as a backdrop will give
you an idea of the spatial resolution of the image. Given the choice, our
reviewers would rather have higher resolution imagery, but not at the
expense of system performance or file size limitations (Figure 3).
Figure 3. Zoomed in view with orthophoto backdrop.
Tabular data is available almost as a user would find it in a soil survey
report, with a few exceptions. For example, tables in the hard copy soil
survey lists data ranges as one data field for certain properties like pH,
permeability and water table depth. SoilView maintains the original
MUIR table structure, which has a data field for both the minimum and
maximum values of a given soil property. An example of the "Soil and Water"
table follows (Figure 4).
Figure 4. Portion of Soil and Water Table
The text of the soil survey is available from the menu as a stand-alone
hyper-media file, and functions like a Windows Help file with pop-up
windows, and hyper-links to other text or graphics.The following two
figures give an example of the text capabilities (Figures 5 and 6).
Figure 5. Sample of soil survey manuscript window
Figure 6. Soil map unit description and hypertext Legend
Where the project is now
The alpha release was reviewed by 10-15 people during the months of
January-March, 1996. Work on the beta release, and the funding of it,
will be complete by June, 1996. Several features that will be attempted
to incorporate in the beta include:
- Generic layout capability
- Query save/re-execute capability
- Hyper-links from the text to tables
- Hot links for soil series and map unit descriptions
What's ahead ?
All of the responses received from review of the alpha release were very
favorable, in terms of ease of use, and more importantly, the concept of
providing the user a bundled package of software and data. This product
could reduce the time between completion of field work for a survey and
publication an estimated 4 to 6 times. We will be proposing this product
as an additional and preferred means of publishing soil surveys for the
NRCS, and hope to pursue additional enhancements of this product.
ACKNOWLEDGMENTS
This work was supported in part by the NRCS National Soil Survey Center.
Avenue programming performed by Scott Eichman and Dan Schreiber,
Global Information Systems Technology, Inc. , 100 Trade Center Drive,
Champaign, Illinois 61820 (217-352-1165).
REFERENCES
Indorante, S.J., R.L.McLeese, R.D.Hammer, B.W.Thompson, D.L.Alexander.
1996. Positioning soil survey for the 21st century. J.Soil and Water
Conservation 51:21-28.
Valentine, K.W.G., W.C. Naughton and M. Nava. 1981. A questionnaire
to users of soil maps in British Columbia: Results and implications for design
and content. Can.J. Soil Sci. 61: 123-135.
Thomas P. D'Avello
GIS Specialist
USDA-Natural Resources Conservation Service
1902 Fox Drive
Champaign, IL 61820
217-398-5293
davello@sogis.il.nrcs.usda.gov