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Tool Riparian Land Cover Proportions

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donebert edited this page Aug 24, 2022 · 22 revisions

Riparian Land Cover Proportions

Summary

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

Input features may be lines or polygons or both.

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 land cover calculations to only selected reporting unit polygons is not supported in this release.

  • This tool is designed to use a vector line or polygon dataset that represents streams, but any vector line or polygon dataset may be used. Caution should be exercised when interpreting results, particularly when using datasets that do not represent streams.

  • 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.

    • NOTE: ArcGIS software has been improved over the years to analyze larger and larger datasets. However, limits do exist and large datasets can still cause problems. The Riparian Land Cover Proportions calculator can fail if an input Reporting unit feature contains a large number of reporting units and/or the reporting units cover a significantly large geographical area. Often this type of failure will manifest itself in a Failed to execute (Intersect) error. See Failed to execute (Intersect) for possible workarounds.

  • The tool extracts the Reporting unit feature polygons that overlay the Stream 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 (.xml). 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.

  • Stream features may be one or more vector line or polygon datasets. The Buffer distance specifies the distance around the input features for which buffer zones are created.

    • When Stream features is a line dataset, the buffer occurs on both sides of each line.

    • When Stream features is a polygon dataset, the tool treats the polygon perimeters as lines. The buffer occurs on both sides of each polygon perimeter.

  • 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.

  • The user may elect to Add Quality Assurance Fields, Add Area Fields and/or Retain Intermediate Layers Generated During Metric Processing.

    • Choosing to Retain Intermediate Layers saves the intermediate products to one of the following locations:

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

      • When ouput 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.

  • Output field names are taken from the class element's rlcpField attribute in the specified Land cover classification file. If the rlcpField attribute is not provided, the following naming scheme applies (Refer to Classes Element in ATtILA's LCC XML Document for general information, or the individual Land cover classification file for details):

    • r[class][buffer distance] - The percent of the total buffered area in the reporting unit occupied by the land cover class. For example, values in a field named "rfor100" would represent the percent of land occupied by the NLCD "Forest" class within all 100-meter buffers in the reporting unit.

    • 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.

    • NOTE: Output field names can be altered by editing the Land cover classification file.

Syntax

RLCP (Reporting_unit_feature, Reporting_unit_ID_field, Land_cover_grid, Land_cover_classification_scheme, Land_cover_classification_file, Report_metrics_for_these_classes, Stream_features, 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
Stream_features The vector line and/or polygon dataset(s) that provide the basis for the buffer zones.

Land cover metrics are calculated for the area within the buffer zones.		 Feature layer
Buffer_distance The distance around the Stream 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

Fields Added

  • RLCP_OVER - The percent overlap between the Stream features buffer areas in each reporting unit and the Land cover grid.

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

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

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

  • r[class][buffer distance]_A - The area of the rasterized Stream features buffer, by reporting unit, occupied by the land cover class (e.g. "rfor100_A" is the name of the field for the metric representing the area of NLCD "Forest" class within the rasterized buffer area in each reporting unit).

Intermediate Files Retained

  • rlcp_Buffer[buffer distance]* vector - A polygon feature class containing all Stream features buffered by the selected buffer distance within each reporting unit. The name of the intermediate feature class has the prefix "rlcp_Buffer" followed by the buffer distance, then a number (e.g. rlcp_Buffer1000, rlcp_Buffer1001, rlcp_Buffer500, etc.). The number suffix is added when the feature class is saved in order to give each successive feature class a unique name when the tool is executed more than once and results saved to the same output location.

  • rlcpTabArea* table - A table of areas corresponding to the values in the Land cover raster within each reporting unit. The name of the intermediate table has the prefix "rlcpTabArea" followed by a number (e.g. rlcpTabArea0, rlcpTabArea1, rlcpTabArea2, etc.). The number suffix is added when the table is saved in order to give each successive table a unique name when the tool is executed more than once and results saved to the same output location.

Tool Messages (Example)

Code Samples

Riparian Land Cover Proportions example (Python window)

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.



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