Create Skim

See also

• MMA Key Terms - Skims

This is the geoprocessing interface for the summarizeAccessibility function in the mma module.

Network dataset : ArcGIS Network Dataset or Network Dataset Layer

The network dataset used to find shortest paths between origin locations and destination locations.

Impedance attribute : String

The name of the impedance attribute in network dataset to be used in determining shortest paths between origin locations and destination locations (options are shown with units listed alongside each impedance attribute’s name).

Cutoff value : Float, optional

The maximum impedance attribute value from origin locations beyond which destination locations will not be tabulated in the skim. If no value is provided, no cutoff is applied. Applying a cutoff can reduce run times and focus the skim content on relevant destinations.

Number of destinations to find : Integer, Optional

The maximum number of destination locations to find for each origin location. If no value is provided, all destinations (within the cutoff value) will be found.

Apply restrictions : [String,…]

The restriction attributes in network dataset to honor when finding shortest paths (“Oneway;PedesetrianOnly” e.g.). If no restriction attributes exist in the network dataset this field in the geoprocessing interface will be empty.

U-turn policy : {“ALLOW_UTURNS”, “NO_UTURNS”, “ALLOW_DEAD_ENDS_ONLY”, “ALLOW_DEAD_ENDS_AND_INTERSECTIONS_ONLY”}

The u-turn policy to honor when finding shortest paths.

Origin locations : ArcGIS Feature Class or Feature Layer

An ArcGIS point feature class or point feature layer in the active data frame representing origin locations to be recorded in the skim(s).

Origin ID field : Field

Field in origin locations to use as the origin ID value when tabulating travel times in the skim(s).

Group Origins : Boolean, optional

(Default is False.) If checked (true), origins will be grouped for processing. Grouping limits the number of features included in a given OD matrix tabulation to manage memory and output file sizes. If unchecked (false), all origins will be evaluated as a single group.

Reference layer for grouping origins : ArcGIS Feature Class or Feature Layer, optional

If group origins is checked (true), origins will be grouped based on the spatial relationship of features in origin features to features in this layer.

Origin group ID field : Field, optional

Name of the field in reference layer for grouping origins that organizes the grouping of origin locations. Distinct values in this field will be included in output file names to relate each skim table to its origin group.

Selection method : String, optional

The spatial relationship to apply when grouping origin locations based on reference layer for grouping origins. All ArcGIS overlap_types are valid.

Selection radius : Linear Unit, optional

The distance to search around reference layer for grouping origins for testing their spatial relationship to origin locations. If no value is provided a strict spatial relationship among featues will be applied (i.e., no search radius).

Destination features : ArcGIS Feature Class or Feature Layer

An ArcGIS point feature class or point feature layer in the active data frame representing destination locations to be recorded in the skim(s).

Destination ID field : Field

Field in destination locations to use as the destination ID value when tabulating travel times in the skim(s).

Use network locations : Boolean, optional

If checked (true), origin locations and destination locations will load on to the network dataset using pre-calculated values stored in various fields stored in their respective attribute tables. If unchecked (false), origin locations and destination locations will load on to the network dataset based on spatial criteria (this takes longer and can lead to inconsistencies in loading locations).

Origin SourceID/SourceOID/PosAlong/SideOfEdge/SnapX/SnapY/Distance field : Field, optional

If use network locations is checked (true), provide the names of the network location fields in the origin locations layer’s attributes table. Each field specifies a portion of the pre-calculated network location.

Destination SourceID/SourceOID/PosAlong/SideOfEdge/SnapX/SnapY/Distance field : Field, optional

If use network locations is checked (true), provide the names of the network location fields in the destination locations layer’s attributes table. Each field specifies a portion of the pre-calculated network location.

Search tolerance units : Linear unit, optional

If use network locations is unchecked (false), specify the maximum distance from a network dataset source listed in network location search criteria to search for origin locations and destination locations for loading. Features beyond the search tolerance units will be ignored during loading. (Default is “5000 Meters”.)

Network location search criteria : [String,…]

If use network locations is unchecked (false), list the network sources and snapping points on which origin locations and destination locations may load.

Match to closest : Boolean, optional

If use network locations is unchecked (false), specify how to select loading locations based on network dataset sources listed in network location search criteria. If match to closest is checked (true), features will load on the closest valid source. If match to closest is unchecked (false), features will honor the priority of network dataset sources implied by the order in which they are listed in network location search criteria, loading on the closest in a given priority group.

Exclude restricted portions of the network : Boolean, optional

If use network locations is unchecked (false), specify whether origin locations and destination locations can be loaded on excluded network features. Excluded features are those honored as restricted as listed in apply restrictions. If exclude restricted portions… is checked (true), excluded features will be ignored during network loading. If exclude restricted portions… is unchecked (false), some locations may load on restricted features.

Additional criteria for loading on edges : String (edge source feature), optional

If use network locations is unchecked (false), optionally specify which network dataset features are available for loading. This field points to a particular edge source feature class for additional querying (see search criteria below).

Search criteria : SQL Expression, optional

If use network locations is unchecked (false), optionally specify which network dataset features are available for loading. This is an expression string to be applied to additional criteria… above that further constrains loading beyond the limits set by network location search criteria, match to closest, and exclude restricted… parameters.

Output workspace : ArcGIS workspace

ArcGIS Workspace (file folder, geodatabase, etc.) where output skim tables will be stored.

Analysis name : String

A string of characters to include in the names of output files to differentiate them from other files produced in the same output workspace. Short strings of 7 characters or fewer are recommended.

Use time of day : Boolean, optional

If checked (true) the network dataset is time-enabled and the user desires skims for a specific day and time(s). If unchecked (false), no differentiation by time of day will be considered.

Day of week : {“Today”, “Monday”, “Tuesday”, “Wednesday”, “Thursday”, “Friday”, “Saturday”}, optional

If use_time_of_day is checked (true), time of day differences will be based on the day of week specified here.

Time window start : Date/time, optional

If use time of day is checked (true), the first time on day of week to be analyzed. Multiple skims can be produced based on the time window end and time window increment… values.

Time window end : Date/time, optional

If use time of day is checked (true), the last time on day of week to be analyzed. Multiple skims can be produced based on the time window end and time window increment… values. If only a single time of day skim is required, set time window end equal to time window start.

Time window increment in minutes : Float, optional

If use time of day is checked (true), the interval at which to increment the time so that multiple skims will be produced for every interval of time window increment between time window start and time window end.

See also

mma.createSkims, mma.Skim