accessing and using statewide aggregated soil survey data

CUSTOM QUERIES FOR SOIL DATA

http://sdmdataaccess.nrcs.usda.gov/

Outline

Basic Soil Data Concepts Aggregation “Traditional” Soil Survey Products Soil Data Access

Soil Survey Manual

Challenges to Spatially Displaying Soils Data The SSURGO soil database has multiple “one

to many relationships”.

Most map units have more than one component, especially when minor components are included.

Most components have multiple horizons.

○ Horizons can contain many different kinds and sizes of fragments

Ultimately need to come to one value for the map unit.

So, I want a map of the soil erodibilty factor (Kf)………….

0.020.020.020.020.020.020.1

0.150.150.150.150.170.170.170.170.170.280.280.32

Or a map of the T (tolerable soil loss) Factor…...

Aggregation Options..

Dominant Component: Returns the value of the component that comprises the highest percentage of the unit.

Aggregation Options..

Dominant Condition: Components are grouped by “condition” and the “condition” with the highest sum percentage is reported

T %5 354 40

Aggregation Options..

Most Limiting Condition: The most limiting “condition” is reported

Soil Data Mart

Houses the Official Soil Survey Data All products discussed get their data

from the Soil Data Mart

Web Soil SurveyInteractive Mapping Service that hosts soils

data and other basic GIS layersHas a good interface for aggregating soil

properties and

interpretationsLimited to 10,000

acre Area of InterestReal time access to

SDM data

“Traditional” Soil Survey Products

Soil Data Viewer Free ArcGIS extension (not programmed

for ArcGIS 10 yet ) Uses SSURGO spatial and tabular data

from the Soil Data Mart Great for single county datasets or small

groups of counties. Good, but limited

aggregation soil properties

Access Template for Tabular Data Tabular data from the Data mart is

imported into Great for creating custom queries

The New Kid on the Block…Soil Data Access

Provides access to the spatial and tabular aspects of the Soil Data Mart by means that are not being met by the WSS and the SDM

Is essentially a suite of Web Services This presentation will focus on the tabular

aspects and querying for custom data.

http://sdmdataaccess.nrcs.usda.gov/

Wisconsin’s approach to providing access to data using the Soil Data Access Site

Create queries that would return statewide aggregated soil propertiesFrom the official data

Document the properties returned and the aggregation methods used

Publish the queries and methodology. Updating regularly based on USER input and requestshttp://www.wi.nrcs.usda.gov/technical/soil/

soils_products.htm Include “mukey” as both a text field and as a number

Why MUKEY and not MUSYM?

Querying the Database

Standard SQL statements Select, From, where, order by.

Can select into temp tables A good understanding of the database

structure is needed (http://sdmdataaccess.nrcs.usda.gov/documents/TableRelationshipsDiagram.pdf)

Outer Joins are defined as Left or Right Joins

The SSURGO metadata is a great resource

SSURGO Metadata http://soildatamart.nrcs.usda.gov/SSURGOMetadata.aspx

Pre-Packaged Aggregated Attributes

Data elements in the Mapunit table Data elements in the MUAGGATT table

Try not to use the hydclprs field…

SELECT mu.musym, mu.muname, mu.mukind, mu.farmlndcl, mu.mukey,

cast (mu.mukey as int) as mukey_num

FROM sacatalog sac

INNER JOIN legend l ON l.areasymbol = sac.areasymbol and l.areasymbol LIKE 'WI%'

INNER JOIN mapunit mu ON mu.lkey = l.lkey

ORDER BY l.areasymbol, mu.museq