The Snap to Network tool updates point geometry to be snapped onto a provided polyline network.
You may specify a search distance which is the distance from each feature to search for network elements to snap to. This tool requires a Track ID field as well as a Start Time key field to be specified on the input dataset in order to function. The Track ID field and Start Time date field are required as the track-based sequential and directional nature of observations are leveraged 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 a Track ID and Start Time key fields. The join dataset is a polyline dataset representing a network. This polyline dataset has three required fields in order to function with the Snap to Network tool, more details are provided in the Usage notes below.
- A transportation organization is monitoring vehicles equipped with automatic vehicle location (AVL) tracking devices. The Snap to Network tool can be utilized to snap observations to their road network in order 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 then be used in a later attribute join to enrich each vehicle observation with the road segment attribute information along which the vehicle is traveling.
- The only requirement for the polyline features network provided to this tool is that the schema of the layer contains the following three fields correctly populated:
- OBJECTID or FID
- F_AUTOMOBI or F_AUTOMOBILE
- T_AUTOMOBI or T_AUTOMOBILE
- The F_AUTOMOBI and T_AUTOMOBI fields indicate the driving direction relative to the digitizing direction of the polyline features. The F_AUTOMOBI and T_AUTOMOBI 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 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 = 'Y' and T_AUTOMOBI = 'N'
- If the driving direction is the same as the digitizing direction, F_AUTOMOBI = 'N' and T_AUTOMOBI = 'Y'
- If the street segment is a two-way street, F_AUTOMOBI = 'Y' and T_AUTOMOBI = 'Y'
- 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 missing essential elements 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
The point features which will be snapped to the network based on user-defined parameters.
This dataset must have Track ID and Start Time key fields defined.
The polyline features representing a network to which features will be snapped.
The layer must have the following three fields:
The distance from each point feature to search for network features to snap to.
Track ID Field(s)
The fields which uniquely identify observations. If the Track ID key field is already identified on the input dataset, it will be automatically picked up.
If a Track ID field has not been specified on the input dataset, this parameter must be used to identify the Track ID field(s) that uniquely identify observations.
Split Duration (Optional)
The amount of time between observations which if exceeded will break the processing out to a separate track.
Split Distance (Optional)
The distance between observations which if exceeded will break the processing out to a separate track.
If the incoming features already 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.
The output layer will contain the following attributes appended to the original attributes for each feature.
|Field Name||Description||Field Type|
The original X coordinate of the point.
The original Y coordinate of the point.
The OBJECTID or FID of the network polyline feature that the point feature was snapped to.
The percentage fraction along this polyline upon which the point feature was snapped.
The distance from the original feature to the point along the polyline where it was snapped.
The relative estimated accuracy of the snap operation.
The heading as calculated by the original position of the point (and its immediate prior point).
The heading as calculated by the snapped position of the point (and its immediate prior snapped point).