Letter Features (Defense)

Summary

Adds a sequential letter to a new or existing field of a set of features.

Usage

• Adding a sequential letter scheme to an existing field will overwrite the values in that field.

• Features outside of the Input Area to Letter parameter value will automatically set the Field to Letter (Existing or New) parameter to Null.

• When naming a new field to letter in the Field to Letter (Existing or New) parameter, the first letter must be an alpha character, and the remaining letters must be alphanumeric or underscores.

• When lettering features other than points, all features that are contained in or intersect the Input Area to Letter parameter value will be lettered.

Parameters

Dialog

Label	Explanation	Data Type
Input Features	The input features that will be lettered.	Feature Set
Field to Letter (Existing or New)	The input field that will be lettered. The field must be a new or existing text field.	Field
Input Area to Letter (Optional)	The area that will limit the features to letter; only features within this area will be lettered.	Feature Set
Spatial Sort Method (Optional)	Specifies how features will be spatially sorted for the purpose of lettering. Features are not reordered in the table. Upper right—Features will be sorted starting at the upper right corner. This is the default. Upper left—Features will be sorted starting at the upper left corner. Lower right—Features will be sorted starting at the lower right corner. Lower left—Features will be sorted starting at the lower left corner. Peano curve—Features will be sorted using a space-filling curve algorithm, also known as a Peano curve. Center—Features will be sorted starting from a center point (the mean center will be used if no center is provided). Clockwise—Features will be sorted starting from a center point and moving clockwise. Counterclockwise—Features will be sorted starting from a center point and moving counterclockwise. None—No spatial sort will be used. The same order as the feature class will be used.	String
Lettering Format (Optional)	Specifies the labeling format that will be used for each feature. Excel (A, B, C, ...)—An alpha character (for example, A, B, C) will be used. This is the default. Grid (AA, AB, AC, ...)—A constant alpha character with an incrementing second alpha character grid (for example, AA, AB, AC) will be used. Alternating Grid (AA, BB, CC, ...)—A double alpha character that is incremented for each feature (for example, AA, BB, CC) will be used.	String
Starting Letter (Optional)	The value that will be used to begin lettering.	String
Omit Letters (Optional)	The values that will be omitted from the lettering sequence.	String
Center Point (Optional)	The center point that will be used to sort and letter features.	Feature Set
Add Distance and Bearing to Center (Optional)	Specifies whether fields will be added to the output for distance and bearing to a center point. Do not add distance and bearing—No distance or bearing fields will be added to the output. This is the default. Add distance and bearing—DIST_TO_CENTER and ANGLE_TO_CENTER fields will be added to the output.	Boolean

Derived Output

Label	Explanation	Data Type
Output Feature Class	The updated feature class.	Feature Class

Python

arcpy.defense.LetterFeatures(in_features, field_to_letter, {in_area}, {spatial_sort_method}, {lettering_format}, {starting_letter}, {omit_letters}, {center_point}, {add_distance_and_bearing})

Name	Explanation	Data Type
in_features	The input features that will be lettered.	Feature Set
field_to_letter	The input field that will be lettered. The field must be a new or existing text field.	Field
in_area (Optional)	The area that will limit the features to letter; only features within this area will be lettered.	Feature Set
spatial_sort_method (Optional)	Specifies how features will be spatially sorted for the purpose of lettering. Features are not reordered in the table. UR—Features will be sorted starting at the upper right corner. This is the default. UL—Features will be sorted starting at the upper left corner. LR—Features will be sorted starting at the lower right corner. LL—Features will be sorted starting at the lower left corner. PEANO—Features will be sorted using a space-filling curve algorithm, also known as a Peano curve. CENTER—Features will be sorted starting from a center point (the mean center will be used if no center is provided). CLOCKWISE—Features will be sorted starting from a center point and moving clockwise. COUNTERCLOCKWISE—Features will be sorted starting from a center point and moving counterclockwise. NONE—No spatial sort will be used. The same order as the feature class will be used.	String
lettering_format (Optional)	Specifies the labeling format that will be used for each feature. A_B_C—An alpha character (for example, A, B, C) will be used. This is the default. AA_AB_AC—A constant alpha character with an incrementing second alpha character grid (for example, AA, AB, AC) will be used. AA_BB_CC—A double alpha character that is incremented for each feature (for example, AA, BB, CC) will be used.	String
starting_letter (Optional)	The value that will be used to begin lettering.	String
omit_letters [omit_letters,...] (Optional)	The values that will be omitted from the lettering sequence.	String
center_point (Optional)	The center point that will be used to sort and letter features.	Feature Set
add_distance_and_bearing (Optional)	Specifies whether fields will be added to the output for distance and bearing to a center point. DONT_ADD_DISTANCE—No distance or bearing fields will be added to the output. This is the default. ADD_DISTANCE—DIST_TO_CENTER and ANGLE_TO_CENTER fields will be added to the output.	Boolean

Derived Output

Name	Explanation	Data Type
out_feature_class	The updated feature class.	Feature Class

Code sample

LetterFeatures example 1 (Python window)

The following Python window script demonstrates how to use the LetterFeatures function.

import arcpy
arcpy.env.workspace = r"C:/Data.gdb"
arcpy.defense.LetterFeatures("bldg_footprints", "bldg_letter")

LetterFeatures example 2 (stand-alone script)

The following example uses the LetterFeatures function in an example workflow script.

# Select buildings with a footprint over 5000 square feet and assign a letter

# Import system modules
import arcpy

# Set environment settings
arcpy.env.workspace = r"C:/Data.gdb"

# Project data
out_coordinate_system = arcpy.SpatialReference(3395)
proj_bldg = "bldg_footprint_proj"
arcpy.management.Project("Buildings",
                         proj_bldg,
                         out_coordinate_system)

# Calculate area
arcpy.management.CalculateGeometryAttributes(proj_bldg,
                                             "area AREA",
                                             '',
                                             "SQUARE_FEET_US")

# Export to a new feature class
expression = "area >= 5000"
arcpy.conversion.FeatureClassToFeatureClass(proj_bldg,
                                            arcpy.env.workspace,
                                            "bldg_over_5000",
                                            expression)

# Letter the buildings
arcpy.defense.LetterFeatures("bldg_over_5000",
                             "bldg_letter",
                              None,
                              "CENTER",
                              "A_B_C",
                              "A",
                              "D",
                              "neighborhood_center",
                              "ADD_DISTANCE")

Environments

Extent, Current Workspace, Scratch Workspace