Tool Sample Point Land Cover Proportions - USEPA/ATtILA2 Wiki

Sample Point Land Cover Proportions

Summary

Calculates the percentages of selected land cover types within the area adjacent to input point features in each reporting unit and creates an output table.

Adjacency is determined by a buffer distance specified by the user.

Additionally, reporting unit boundaries can be selected to act as an absolute barrier when creating buffer areas or ignored. If boundaries are enforced, buffer areas for features outside of the reporting unit will stop at the reporting unit boundary, elsewise buffer areas for features outside of the reporting unit are allowed inside the reporting unit.

Usage

  • This tool processes all polygons in the Reporting unit feature regardless of selections set. The ability to limit calculations to only selected reporting unit polygons is not supported in this release.

  • The Reporting unit feature is a zone dataset.

    • A zone is defined as all areas in the input that have the same value. The areas do not have to be contiguous. The term "value" in this definition refers to the unique values in the Reporting unit ID field. Therefore, all polygons with the same reporting unit ID are treated as a single zone.

    • When more than one polygon has the same reporting unit ID, the areas for each polygon are combined and metrics are reported as a single record in the Output table.

  • The tool extracts the Reporting unit feature polygons that overlay the Sample point features buffers using an Intersect and Query. This results in an intermediate polygon feature class containing multipart features of all buffer areas in each reporting unit. The tool then performs a vector to raster conversion of the multipart features to create zones for each reporting unit.

    • To better control the vector to raster conversion, the tool defaults the Snap raster and the Processing cell size to that of the Land cover grid. These may be changed from within the tool.

    • If a large size disparity exists between the extents of the Reporting unit feature and the Land cover grid, the user may wish to set the Extent in Environment Settings > Processing Extent to the smaller of the two to avoid unnecessary processing.

  • If the Reporting unit feature has overlapping features, the zonal analysis will be performed for each individual feature.

  • If a feature in the Reporting unit feature zone data does not overlap any cell centers in the secondary class rasters (e.g.,Land cover grid), those zones will not get converted to the internal zone raster. As a result, those zones will not be represented in the Output table.

  • The Land cover classification scheme must correspond to the Land cover grid.

    • Schemes for common land cover datasets are included with ATtILA. Supplied schemes may be designated as either "ALL" or "LAND" (e.g. NLCD 2001 ALL vs. NLCD 2001 LAND). Schemes designated as "ALL" include all land cover classes in the metric calculations, while those designated as "LAND" include only terrestrial land cover classes, with non-terrestrial land cover classes such as water and snow/ice excluded. More information about each of the classification schemes supplied with ATtILA may be found in Supplied Land Cover Classification Schemas.

    • In addition to the common land cover schemes, the tool permits a user-defined land cover classification scheme to be used by specifying a Land cover classification file. Refer to Land Cover Classification for more information.

    • NOTE: When a classification scheme with excluded land cover classes is selected, the areas of the excluded classes are disregarded in metric calculations. For example, when selecting a "LAND" classification scheme, the tool will process individual land cover classes and calculate metrics based on the total terrestrial area they occupy within the reporting unit, rather than the percent of the total area within the reporting unit.

  • If Enforce reporting unit boundaries is selected, Sample point features must contain an attribute that identifies the reporting unit in which each point lies. This attribute is entered in the Reporting Unit Link Field parameter. If no such attribute exists in the Sample point features attribute table, it is recommended that the Identity tool be used. The Identity tool is located in the ArcToolbox under Analysis Tools > Overlay.

  • Final output is written to the location specified in the Output table parameter. The Output table may be saved as a File Geodatabase Table, or a dBASE Table.

    • NOTE: For most consistent results, it is highly recommended that tool output be saved to a file geodatabase.

    • When saving as a File Geodatabase Table, no extension is necessary for the Output table name. The output location must be a file geodatabase.

    • When saving as a dBASE Table, include the .dbf extension in the Output table name. dBASE tables may not be saved in a file geodatabase.

  • Field names in the Output table follow this naming scheme:

    • [class splcpField] or s[class Id][buffer distance] - The percent of the total buffered area in the reporting unit occupied by the land cover class.

      • [class splcpField] is used if an splcpField attribute is provided in the class's element in the selected Land cover classification file.

        • (e.g., NearAgr for <class Id="agr" Name="Agriculture" filter="" splcpField="NearAgr">)
      • s[class Id][buffer distance] - is used if an splcpField attribute is not provided.

        • (e.g., sagr100 for <class Id="agr" Name="Agriculture" filter=""> and a 100-meter buffer distance used)
    • NOTE: Output field names can be altered by editing the Land cover classification file with the Land Cover Classification Editor (Refer to Classes Element in ATtILA's LCC XML Document for general information, or the individual Land cover classification file for details).

    • NOTE: The output field name for each class is shown as the second item next to the class's check box in Report metrics for these classes.

  • In Additional Options, the user may elect to 'Add Quality Assurance Fields', 'Add Area Fields', and/or 'Retain Intermediate Layers Generated During Metric Processing'.

    • Add Area Fields

      • Choosing AREAFIELDS adds fields to record the raster area measurement of the selected land cover classes occuring in a buffer area within each reporting unit. The field naming conventions is dependent on whether an splcpField is provided in the Land cover classification file:

        • [class splcpField]_A or s[class Id][buffer distance]_A - The area of the rasterized Sample point features buffer, by reporting unit, occupied by the land cover class.
    • Add Quality Assurance Fields

      • Choosing QAFIELDS adds a number of fields to the Output table to facilitate quality assurance checking.

        • SPLCP_OVER - The percent overlap between the Sample point features buffer areas in each reporting unit and the Land cover grid.

        • SPLCP_TOTA - The total raster zonal area for all Sample point features buffers in each reporting unit (zone) after the buffer areas have been rasterized.

        • SPLCP_EFFA - The effective raster area of all Sample point features buffers in each reporting unit (zone) after excluded classes have been removed.

        • SPLCP_EXCA - The raster area of the excluded classes within the Sample point features buffers in each reporting unit (zone) based on exclusions in the Land cover classification scheme.

        • sBUFF[buffer distance] - The percentage of the reporting unit comprised of the Sample point features buffer area.

    • Retain Intermediate Layers Generated During Metric Calculation

      • Choosing INTERMEDIATES retains several of the key intermediate products (e.g., rasters, feature classes, tables) used to generate the final tool output. By examining the intermediate products, the user can gain a better understanding how the metric is calculated. The following intermediate products are listed in the general order they are generated:

        • splcp_[Sample point features]_Buffer# (vector) - This feature class is only produced when the optional Enforce reporting unit boundaries selection is NOT checked.

        • splcp_Merge# (vector) - This feature class is only produced when the optional Enforce reporting unit boundaries selection is NOT checked.

        • splcp_Intersect# (vector) - This feature class is only produced when the optional Enforce reporting unit boundaries selection is NOT checked.

        • splcp_Buffer[buffer distance]# (vector) - A polygon feature class containing all Sample point features buffered by the selected buffer distance within each reporting unit.

        • splcpTabArea# (table) - A table of areas corresponding to the values in the Land cover raster occuring in the buffer area within each reporting unit.

        • NOTE: To ensure unique filenames, intermediate filenames are typically generated using the CreateScratchName ArcPy function. This function provides a unique name for the intermediate product by appending a number to a filename prefix. The number starts at 0 and is incremented until a unique filename for the output workspace is found. The generated number is represented in this manual by the hashtag (#) symbol.

        • NOTE: The appended number may not be the same for all intermediate products saved during a tool run. Running a tool with different input options can result in different intermediate products being produced. If a tool is run more than once using the same output workspace, different number suffixes may be generated depending on the files already present in the output workspace.

      • Intermediate products are saved to one of the following locations:

        • When the Output table is saved as a File Geodatabase Table, intermediate products are placed in the same file geodatabase.

        • When the Output table is saved as a dBASE Table, a file geodatabase named "attilaScratchWorkspace" is automatically generated in the same output location specified for the Output table. Intermediate products are placed in the attilaScratchWorkspace file geodatabase.

        • NOTE: ATtILA will report the location of the saved intermediate products in the Tool Details' Messages section.

Syntax

SPLCP (Reporting_unit_feature, Reporting_unit_ID_field, Land_cover_grid, Land_cover_classification_scheme, Land_cover_classification_file, Report_metrics_for_these_classes, Sample_point_features, RU_Link_Field, Buffer_distance, Output_table, {Processing_cell_size}, {Snap_raster}, Select_options)

Parameter Explanation Data Type
Reporting_unit_feature The vector polygon dataset that defines the reporting units. Feature Layer
Reporting_unit_ID_field The field in the Reporting unit feature layer that contains the unique ID for each reporting unit.

It may be an integer or a string data type.
Field
Land_cover_grid The raster dataset representing land cover classes to be summarized within each Reporting unit feature.

The grid input must be an integer raster layer.
Raster Layer
Land_cover_classification_scheme The land cover classification schemes included in ATtILA and a User Defined option.

The default schemes correspond to common input land cover datasets. Two schemes are supplied for each dataset included in ATtILA:

  • {DATASET NAME} ALL - includes all land cover types in the grid with no exclusions.
  • {DATASET NAME} LAND - excludes non-terrestrial land cover types.
String
Land_cover_classification_file The full pathname to the user-defined .xml file for custom or non-standard land cover classification schemes.

Pathname is automatically filled when a default scheme is selected.
File
Report_metrics_for_these_classes A list of the land cover classes and metric combinations for processing.

Check the box to calculate metrics for each land cover class and/or combination class desired within the reporting units.
Multiple Value
Sample_point_features The vector point dataset that provides the basis for the buffer zones.

Land cover metrics are calculated for the area within the buffer zones.
Feature layer
RU_Link_Field The field in the Sample point features layer that contains the unique ID for each reporting unit.

It may be an integer or a string data type.
Field
Buffer_distance The distance around the Sample point features which comprises the buffer zones.

The value must be an integer.

If the distance linear units are not specified or are entered as Unknown, the linear unit of the input features' spatial reference is used.
Linear unit
Enforce_reporting_unit_boundaries Specifies whether a Reporting unit boundary acts as an absolute barrier when creating buffer areas.

  • false - Buffer areas for features outside of the reporting unit are allowed inside the reporting unit boundary.
  • true - Buffer areas for features outside of the reporting unit will stop at the reporting unit boundary. This is the default.
Boolean
Output_table The output reporting unit metrics table to be created.

It is recommended that the Output table be saved within a file geodatabase.
Table
Processing_cell_size (Optional) The Processing cell size for the zonal operation.

The default Processing cell size is the cell size of the input raster land cover data. Optionally, the user may select a different cell size.
Analysis cell size
Snap_raster (Optional) The raster that the cell alignment of the Land cover grid and rasterized Reporting unit feature layer will be matched to during processing.

The default Snap raster is the Land cover grid.
Raster Layer
Select_options Three tool options are available to provide additional information:

  • Add Quality Assurance Fields - Adds area fields to the Output table to facilitate quality assurance checking.
  • Add Area Fields for All Land Cover Classes - Adds fields to the Output table that includes the areas of each land cover class and combination class selected.
  • Retain Intermediate Layers Generated During Metric Calculation - Saves the intermediate table and/or raster that is normally deleted after processing is complete.
Multiple Value

Code Samples

Sample Point Land Cover Proportions example 1 (Python window)

This example returns a table with the proportion of the area within 500 meters of a sample point within the reporting unit zone comprised of the agriculture and the developed land cover classes. The option to retain the intermediate calculation products has also been selected.

NOTE: ATtILA tools that utilize the Report metrics for these classes parameter will clear all class selections when the tool is opened. This results in setting any variable set for that parameter to None when calling the tool from a script. Because of this, the standard scripting syntax (e.g. arcpy.ATtILA.LCP(variable 1, variable 2, variable 3, etc.) will fail. To overcome this idiosyncrasy, use the scripting example provided below. When using this technique, all variables are passed in as strings.

import arcpy
from arcpy.sa import *
arcpy.ImportToolbox(r"D:\Destination Folder\ATtILA v2.tbx")
from ATtILA2 import metric

Reporting_unit_feature = r"D:\pyexamples\data.gdb\Watersheds"
Reporting_unit_ID_field = "HUC_12"
Land_cover_grid = r"D:\pyexamples\data.gdb\NLCD_2016"
Land_cover_classification_scheme = "NLCD LAND"
Land_cover_classification_file = r"D:\Destination Folder\ToolboxSource\LandCoverClassifications\NLCD LAND.xml"
Report_metrics_for_these_classes = "'agr  -  [sagr]  Agriculture';'dev  -  [sdev]  Developed'"
Sample_point_features = r"D:\pyexamples\data.gdb\SampleSites"
Reporting_unit_link_field = "HUC_12"
Buffer_distance = "500 Meters"
Enforce_reporting_unit_boundaries = "true"
Output_table = r"D:\pyexamples\results.gdb\Watersheds_SPLCP"
Processing_cell_size = "30"
Snap_Raster = r"D:\pyexamples\data.gdb\NLCD_2016"
Select_options = "'INTERMEDIATES  -  Retain Intermediate Layers Generated During Metric Calculation'"




metric.runSamplePointLandCoverProportions(Reporting_unit_feature,
                                          Reporting_unit_ID_field,
                                          Land_cover_grid,
                                          Land_cover_classification_scheme,
                                          Land_cover_classification_file,
                                          Report_metrics_for_these_classes,
                                          Sample_point_features,
                                          Reporting_unit_link_field,
                                          Buffer_distance,
                                          Enforce_reporting_unit_boundaries,
                                          Output_table,
                                          Processing_cell_size,
                                          Snap_Raster,
                                          Select_options)

Sample Point Land Cover Proportions example 2 (Tool Details Messages)

This is a sample capture of the geoprocessing messages generated during a typical tool run. It is provided here to assist in the understanding of the tool's processing steps.


Start Time: Day, Month dd, yyyy hh:mm:ss AM/PM
Started: yyyy-mm-dd hh:mm:ss Setting up environment variables
Intermediates are stored in this directory: workspace path
Buffering input features...
Clipping buffered features to each reporting unit...
1 out of 4 loops, 25.0% complete, 0:00:01 elapsed, est. hh:mm:ss remaining, average time per loop: hh:mm:ss
2 out of 4 loops, 50.0% complete, 0:00:03 elapsed, est. hh:mm:ss remaining, average time per loop: hh:mm:ss
3 out of 4 loops, 75.0% complete, 0:00:05 elapsed, est. hh:mm:ss remaining, average time per loop: hh:mm:ss
4 out of 4 loops, 100.0% complete, 0:00:07 elapsed, est. hh:mm:ss remaining, average time per loop: hh:mm:ss
Time: yyyy-mm-dd hh:mm:ss Constructing the ATtILA metric output table
Time: yyyy-mm-dd hh:mm:ss Generating a zonal tabulate area table
Time: yyyy-mm-dd hh:mm:ss Processing the tabulate area table and computing metric values
Succeeded at Day, Month dd, yyyy hh:mm:ss AM/PM (Elapsed Time: ##.## units)

Tags

There are no tags for this item.

Credits

There are no credits for this item.

Use Limitations

There are no access and use limitations for this item.

arrow_up Page

⚠️ **GitHub.com Fallback** ⚠️