Difference between revisions of "Carneros Watershed: Map of Soil Erodibility Index"

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== Metadata ==
 
== Metadata ==
  
* Original source of data:
+
* Original source of data: SSURGO
** update
+
* Data analysis: Kathy Pugh and [[Fred Watson]]
** update
+
** update
+
* Data analysis: [[Fred Watson]]
+
 
* Map produced by: Kathy Pugh
 
* Map produced by: Kathy Pugh
 
* Map produced using: [[ArcMap]]
 
* Map produced using: [[ArcMap]]
 
* Coordinate system: Geographic Coordinate System - GCS_North_American_1983
 
* Coordinate system: Geographic Coordinate System - GCS_North_American_1983
 
* Datum: D_North_American_1983
 
* Datum: D_North_American_1983
 +
 +
== Data Analysis Steps Taken ==
 +
 +
# Download SSURGO data
 +
# Receive zip file of zip files, each one like soil_ca069.zip.
 +
# Extract, and open basic shapefile of map-units (MU): soilmu_a_ca069.shp in Arc
 +
# Can't read tables in this zip, because need special MS Access Template
 +
# Download Access template from  http://soildatamart.nrcs.usda.gov/templates.aspx
 +
# Open template in Access; Enable Macros; and it should prompt for location of your tables
 +
# Wait a few minutes while Access imports your tables
 +
# Create some custom queries in Access to extract some kind of Kf for each map unit
 +
## Review the SSURGO data model: http://soildatamart.nrcs.usda.gov/documents/SSURGO_2_2_DataModel_Part_1.pdf
 +
## Each MapUnit contains several Components, each containing several Horizons.
 +
## First query selects the surface horizons:
 +
## - it joins tables muaggatt+component+chorizon,
 +
## - joining on keys mukey and cokey
 +
## - selecting only horizons whose hzdept_r is 0 (i.e. surface horizons)
 +
## - includes the kffact (Kf-factor) and comppct_r (Percentage of map-unit occupied by Component) fields that will be used below
 +
## Second query takes first as input, and is a MakeTable query, making the table that will be used in Arc
 +
## - computes an expression 'yournamekf: Sum([comppct_r]*[kffact]/100)'
 +
## - it is a Summation query, and the Summation is done on the yournamekf field (above)
 +
## - the other two fields are musym and mukey, and they are GroupBy fields
 +
## Run the second query; it will make a table
 +
## Export the table to DBF format (one way of getting it to Arc)
 +
# Back in Arc, add the DBF table as a layer
 +
# Join the soilmu_a_ca069.shp layer to the DBF layer, using the mukey
 +
# Change the soilmu_a_ca069.shp symbology to display quantitative based on the yournamekf field
  
 
== Alternate versions ==
 
== Alternate versions ==

Latest revision as of 07:44, 28 February 2011

Carneros Watershed: Soil Erodibility Index Map

Metadata

  • Original source of data: SSURGO
  • Data analysis: Kathy Pugh and Fred Watson
  • Map produced by: Kathy Pugh
  • Map produced using: ArcMap
  • Coordinate system: Geographic Coordinate System - GCS_North_American_1983
  • Datum: D_North_American_1983

Data Analysis Steps Taken

  1. Download SSURGO data
  2. Receive zip file of zip files, each one like soil_ca069.zip.
  3. Extract, and open basic shapefile of map-units (MU): soilmu_a_ca069.shp in Arc
  4. Can't read tables in this zip, because need special MS Access Template
  5. Download Access template from http://soildatamart.nrcs.usda.gov/templates.aspx
  6. Open template in Access; Enable Macros; and it should prompt for location of your tables
  7. Wait a few minutes while Access imports your tables
  8. Create some custom queries in Access to extract some kind of Kf for each map unit
    1. Review the SSURGO data model: http://soildatamart.nrcs.usda.gov/documents/SSURGO_2_2_DataModel_Part_1.pdf
    2. Each MapUnit contains several Components, each containing several Horizons.
    3. First query selects the surface horizons:
    4. - it joins tables muaggatt+component+chorizon,
    5. - joining on keys mukey and cokey
    6. - selecting only horizons whose hzdept_r is 0 (i.e. surface horizons)
    7. - includes the kffact (Kf-factor) and comppct_r (Percentage of map-unit occupied by Component) fields that will be used below
    8. Second query takes first as input, and is a MakeTable query, making the table that will be used in Arc
    9. - computes an expression 'yournamekf: Sum([comppct_r]*[kffact]/100)'
    10. - it is a Summation query, and the Summation is done on the yournamekf field (above)
    11. - the other two fields are musym and mukey, and they are GroupBy fields
    12. Run the second query; it will make a table
    13. Export the table to DBF format (one way of getting it to Arc)
  9. Back in Arc, add the DBF table as a layer
  10. Join the soilmu_a_ca069.shp layer to the DBF layer, using the mukey
  11. Change the soilmu_a_ca069.shp symbology to display quantitative based on the yournamekf field

Alternate versions

  • None

Links