Snap to Network

The Snap to Network tool Snap to Network tool updates point geometry to be snapped onto a provided polyline network.

Specify a search distance, which is the distance from each feature to search for network elements to snap to. This tool requires a

The Track ID and a Start Time key fields must be specified on the input dataset to function. The Track ID and the Start Time date field are required, as the track-based sequential and directional nature of observations are used to snap the features to the correct network line feature.

The Snap to Network tool has two input datasets. The target dataset is the point features dataset of observations that have both Track ID and Start Time key fields. The join dataset is a polyline dataset representing a network. This polyline dataset has three required fields to function with the Snap to Network tool. Additional details are provided in the Usage notes section below.

Examples

  • A transportation organization is monitoring vehicles equipped with automatic vehicle location (AVL) tracking devices. The Snap to Network tool can be used to snap observations to a road network to improve the accuracy of the AVL GPS observations.
  • A city is monitoring snowplow operations and wants to better understand vehicle movement. The Snap to Network tool can be used to snap observations to the city's road network. The LineID attribute will be used in a later attribute join to enrich each vehicle observation with the road segment attribute information for the road along which the vehicle is traveling.

Usage notes

  • The only requirement for the polyline features network provided to this tool is that the schema of the layer must contain the following three fields, correctly populated:
    • OBJECTID or FID
    • F_AUTOMOBI or F_AUTOMOBILES
    • T_AUTOMOBI or T_AUTOMOBILES
  • The OBJECTID or FID field provided should contain a unique integer (numeric) value for each polyline feature. If the OBJECTID or FID field is provided as a float, it will be converted to an integer.
  • The F_AUTOMOBI/F_AUTOMOBILES and T_AUTOMOBI/T_AUTOMOBILES fields indicate the driving direction relative to the digitizing direction of the polyline features. The F_AUTOMOBI/F_AUTOMOBILES and T_AUTOMOBI/T_AUTOMOBILES fields should be string fields with a value of either Y or N. If you have fields with these values but with different field names, you can use the Calculate Fields or Map Fields tool to change or generate a copy of these fields with the required names.
    • If the driving direction is against the digitizing direction, F_AUTOMOBI/F_AUTOMOBILES = Y and T_AUTOMOBI/T_AUTOMOBILES = N.
    • If the driving direction is the same as the digitizing direction, F_AUTOMOBI/F_AUTOMOBILES = N and T_AUTOMOBI/T_AUTOMOBILES = Y.
    • If the street segment is a two-way street, F_AUTOMOBI/F_AUTOMOBILES = N and T_AUTOMOBI/T_AUTOMOBILES = N.
  • The Split Distance, Split Duration, and Heading parameters are optional.
  • If some features from the target features being snapped are missing geometry, Track ID values, or start time values, these features will be discarded from the snapped features.
  • If some features from the network features are missing geometry, these features will not be considered in the snapping operation.

Parameters

ParameterDescriptionData type

Input Layer

The point features that will be snapped to the network based on user-defined parameters.

This dataset must have Track ID and Start Time key fields defined.

Point Features

Network Layer

The polyline features representing a network to which features will be snapped.

The layer must have the following three fields:

  • OBJECTID or FID
  • F_AUTOMOBI/F_AUTOMOBILES
  • T_AUTOMOBI/T_AUTOMOBILES
The F_AUTOMOBI/F_AUTOMOBILES and T_AUTOMOBI/T_AUTOMOBILES fields indicate the driving direction relative to the digitizing direction of the polyline features. The F_AUTOMOBI and T_AUTOMOBI/T_AUTOMOBILES fields should be string fields with a value of either Y or N. If you have fields with these values but with different names, you can use the Calculate Fields or Map Fields tools to change or generate a copy of these fields with the required names.
  • If the driving direction is against the digitizing direction, F_AUTOMOBI/F_AUTOMOBILES = Y and T_AUTOMOBI/T_AUTOMOBILES = N.
  • If the driving direction is the same as the digitizing direction, F_AUTOMOBI/F_AUTOMOBILES = N and T_AUTOMOBI/T_AUTOMOBILES = Y.
  • If the street segment is a two-way street, F_AUTOMOBI/F_AUTOMOBILES = N and T_AUTOMOBI/T_AUTOMOBILES = N.

Polyline Features

Search Distance

The distance from each point feature to search for network features to snap to.

String

Track ID Field(s)

The fields that uniquely identify observations. If the Track ID key field is identified in the input dataset, it will be automatically picked up.

If a Track ID field has not been specified for the input dataset, this parameter must be used to identify the Track ID fields that uniquely identify observations.

String

Split Duration (Optional)

The amount of time between observations that, if exceeded, will break the processing out to a separate track.

String

Split Distance (Optional)

The distance between observations that, if exceeded, will break the processing out to a separate track.

String

Heading (Optional)

If the incoming features have a heading field with values determined, this can be specified using the heading parameter to improve the network snapping accuracy.

The field specified for the heading must be a numeric field.

String

Join Fields

Select the fields from the network schema to add to the target features.

For example, if a join field of STREET_NAME is chosen, the output schema will have the field STREET_NAME added. If a point is snapped to a street named Main Street, the value for this field will also be Main Street.

String

Feature handling - Retain only snapped features

Specify how the Snap to Network tool should handle features that are not snapped to a network feature.

You can retain only features that are snapped to the network or retain all features regardless of snap success.

If a feature was not snapped successfully, the original geometry will be retained and Snap to Network tool populated fields will be null.

Boolean

Output layer

The output layer will contain the following attributes appended to the original attributes for each feature. Any join fields specified will also be added to the output layer.

Field nameDescriptionField type

OrigX

The original x-coordinate of the point.

Float64

OrigY

The original y-coordinate of the point.

Float64

LineID

The OBJECTID or FID of the network polyline feature that the point feature was snapped to.

Float64

FractionAlong

The percentage fraction along this polyline on which the point feature was snapped.

Float64

DistanceToLine

The distance from the original feature to the point along the polyline where it was snapped.

Float64

SnapScore

The relative estimated accuracy of the snap operation.

Float64

HeadingOriginal

The heading as calculated by the original position of the point (and its immediate prior point).

Float64

HeadingSnapped

The heading as calculated by the snapped position of the point (and its immediate prior snapped point).

Float64