Our online soil survey can be used to access USDA-NCSS 1:24,000 scale detailed soil survey data (SSURGO) in many parts of the lower 48 states. Where this data is not yet available, 1:250,000 scale generalized soils data (STATSGO) can be accessed instead. An interactive map interface allows for panning and zooming, with highways, streets, and aerial photos to assist navigation (Figure 1). Soil polygons become visible near a scale of 1:30,000. Alternatively, a GPS point, CA Zip code, or a street address can be used to zoom in on a specific location. General usage notes and information on how our online soil survey work can be found here. Statistics on who is using our online soil survey can be found here. Technical details on SoilWeb can be found in this publication. Please note that we are currently transitioning to a new server, and planning to have our local copy of the SSURGO, STATSGO, and OSD databases updated in the coming months.
The SoilWeb app is a portable version of the UC Davis California Soil Resource Lab’s Web-based interface to digital soil survey data from USDA’s Natural Resources Conservation Service (NRCS).
Select an Interface to SoilWeb
Online Querying of NRCS Soil Survey Data
Sometimes you are only interested in soils data for a single map unit, component, or horizon. In these cases downloading the entire survey from Soil Data Mart is not worth the effort. An online query mechanism would suffice. The NRCS provides a form-based, interactive querying mechanism and a SOAP-based analogue. These services allow soil data lookup from the current snapshot of all data stored in NASIS.
An Example Implementation
A simple front-end to the SDM-SOAP query mechanism was implemented using the NuSOAP PHP library. We plan to integrate this functionality into our online soil survey in the near future. Although the documentation on how to craft a working SOAP query is very limited, you can get a response by creating a message like this:
Here is approximately how it is done in PHP:
http://sdmdataaccess.nrcs.usda.gov/Spatial/SDMNAD83Geographic.wfs?Service=WFS&Version=1.0.0&Request=GetFeature&OutputFormat=XmlMukeyList&Typename=MapunitPolyNoGeometry&FILTER=<Filter> <Intersect> <PropertyName>Geometry</PropertyName> <gml:Polygon> <gml:outerBoundaryIs> <gml:LinearRing> <gml:coordinates>-118.908508862,38.8086306467 -118.919673024,38.7901219483 -118.874871427,38.7756131355 -118.862298961,38.7924133734 -118.902681975,38.806449763 -118.908508862,38.8086306467</gml:coordinates> </gml:LinearRing> </gml:outerBoundaryIs> </gml:Polygon> </Intersect> </Filter>
Google Earth App
SoilWeb is an interactive, multifaceted interface to USDA-NCSS soil survey information. Our SoilWeb application for Google Earth streams soil map units and point data as you navigate across the lower '48 states. Currently, our system imposes a 30,000 ac. limit (defined by the Google Earth viewport) for streaming detailed soil survey (SSURGO) map unit boundaries. This limit, combined with a 2 second delay before streaming is initiated, helps to reduce CPU load on our server. When viewing landscapes from directly overhead the 30,000 ac. limit is usually sufficient for most soils investigations. However, tilting the camera for oblique views of the landscape (an excellent way of visualizing soil-landscape relationships) causes the viewport to encompass much larger areas, usually exceeding SoilWeb's limit for detailed linework. The solution to this problem is summarized below, and can also be used to save "chunks" of detailed soil survey information for later use or offline browsing.
Step 1: Zoom to a region of interest, just below the 30,000 ac. limit, and pause for 2 seconds while our server processes your query. You can use the small status bar in the upper-left corner of the viewport to determine the current area, survey areas, and time required for processing. Once the linework has been displayed, right-click on the "Soil Polygons" sub-folder of the SoilWeb entry within the list of layers (Fig 1), and choose "copy". This will create a temporary snippet of KML that describes all map unit line work, labels, and associated links visible within the current viewport and place it on your clipboard. You can inspect this KML snippet by pasting it into a text editor.
Step 2: Next, right-click on the "Temporary Places" folder within the list of layers (Fig 2), and choose "paste". This will create a new KML folder within your Temporary Places. You can make this KML snippet permanent by right-clicking on your new snippet and choosing "save place as", or by dragging your snippet into the "My Places" folder above. Finally, disable the SoilWeb network link and adjust the camera position for optimal viewing of your new KML snippet.
A couple of maps generated from a 1km gridded soil property database, derived from SSURGO data where available with holes filled with STATSGO data. Soil properties visualized at this scale illustrate several important soil-forming factors operating within California: sediment source in the Great Valley, the interplay between precipitation and ET, and removal of salts. This database and the details on its creation should be available within a couple of months. This builds on a related post highlighting some of these maps packaged in KMZ format. Check back in a couple of weeks of updates.
Soil Water Storage
The maximum equivalent depth of water (cm) held within the soil profile. Depends on soil texture, soil depth, and rock fragment content. Geographic patterns illustrate basin (higher water storage) vs. upland (lower water storage) soils, and west-side (higher water storage) vs. east-side (lower water storage) valley alluvium. Major rice-growing regions of the Sacramento Valley (in Colusa and Butte Co.) are clearly visible.
The equilibrium pH of water after mixing in a 1:1 ratio with soil. Depends on sediment source, drainage, climate, and landscape position. Geographic patterns illustrate predominantly lower pH values (acid soils) in regions with higher rainfall, and predominantly higher pH values (alkaline soils) in more arid regions. West-side valley alluvium is typically more basic, while east-side valley alluvium is more acidic.
Electrical Conductivity (salinity)
The ease of which an electric current can pass through a soil-water mixture, and an index for the ionic strength (i.e. salinity) of the soil solution. Depends on salt content of the parent material, water table depth, climate, and land management. Geographic patterns illustrate closed basins and arid regions (west-side of the San Joqauin Valley, Owens Valley, Mojave Desert) characterized by salt accumulation. Highly leached soils (soils where precipitation is much greater than evapotranspiration) are generally not affected by salt accumulation.
SoilWeb for the iPhone is a portable version of our online interface to USDA-NRCS digital soil survey data. The application uses the GPS built into the iPhone to acquire your current location, and then submits an HTTP request to our server via the SoilWeb API. A graphical summary of the soils mapped at your current location is presented on-screen, with links to details through our online soil survey, or via the USDA-NRCS official series description (OSD) archive. SoilWeb for the iPhone can be downloaded free of charge from the iPhone App Store. If you are using a computer, then you will likely want to use our Google Earth interface to the these data. Here is a link to a presentation on how the application works.
Graphical User Guide
A short update to a previous post on the visualization of NCSS/USDA soil survey data in Google Earth. The use of the NetworkLink construct, combined with the spatial indexing present in PostGIS, allows for very rapid lookup and presentation of this massive database. Scale-dependant switching between the detailed (SSURGO) and generalized (STATSGO) databases is done through simple area calculation in PostGIS.
Here is the link to the KMZ file. Here is a link to our conventional viewer application, based on Ka-Map / Mapserver, using the same PostGIS back-end (previous post on this). This PLSS KML file is very useful along-side soil survey information.
Feedback is always welcome!
Updated versions of three soils-related KMZ files: 1-km scale, aggregate LCC, CA Storie Index, and soil texture data, derived from SSURGO. These are part of a series of KMZ / raster datasets that will be published soon. See attached files at the bottom of the page. Enjoy!
Added color support to the mini-profiles used in graphical map unit summaries, the Google Earth interface, and iPhone application. SSURGO doesn't contain soil color data, so colors (in Munsell notation) were extracted from the OSD database, and converted into RGB triplets. Using horizon information from the OSD database also results in much more realistic horizonation, as compared to what is stored in older SSURGO databases. Example of the Yolo series soil, from the Yolo County (1972) soil survey: