Drawing lines using "calculate field" in a Real time analytic

GeoAnalyst

Hello Everyone

I'm fairly new to both Velocity and using arcade, so i really hope someone here can help me.

I have a Marinetraffic HTTPS feed showing the locations of vessels.
I am trying to draw a line from each of these vessels to the nearest point on an international maritime boundary.

From what I understand, you add the feed for the vessels, and the line feature layer to a real-time analytic, then using the "geometry" calculation type in the Field calculator you can draw these lines.

What I am really unsure about is how to write the arcade expression to accomplish this.

Any help will be massively appreciated!

ms-teams_aswWwpksZ4.png

Nicole_Phaneuf

Hey @GeoAnalyst 

We can create polylines from a target point feature to the nearest coordinate along a polyline or polygon feature using the Calculate Distance, Join Features, and Calculate Fields tools. Depending on your datasets, you may also need to utilize the Project tool.

In the case of connecting points from a feed to the nearest coordinate from a polyline feature layer, I am using an HTTP Simulator feed with simulated storm location as points. For my polyline data, I've created three polylines along the east coast in an ArcGIS Online hosted feature layer. My goal is to generate a polyline between each storm data point and the nearest coordinate on my polyline dataset.

My first step will be to use the Calculate Distance tool to determine which of the three polylines that a point feature is closest to. I've added my point data feed (SR:4326) and my polyline feature layer (SR:102100) as a data source to my real-time analytic. The Calculate Distance tool can only use the "Near geodesic" spatial search method if both the target and join features are point features, so I've added a Project tool between my feed and the target port of the Calculate Distance tool to ensure that both datasets are using SR:102100 when they are added to Calculate Distance tool. If your point feature does not have X/Y fields, you can use a Calculate Fields tool to create two new fields with the Arcade expressions "return Geometry($feature).X" and "return Geometry($feature).Y".

In the Calculate Distance tool, I've opted for a search radius of 2000 miles and an output distance unit of Miles (the tool will calculate a new field for us with the distance between the point and the nearest coordinate from the polyline data source). The key component here is adding the Track ID (OBJECTID in this example) from the polyline data source as a Join Field, as we will need this in the next tool.

Next, we will connect the Calculate Distance tool to the target port of the Join Features tool and connect the polyline data source to the join port. We will configure an attribute join where both the target and join fields will be the Track ID field we identified in the previous Calculate Distance tool (OBJECTID). We will choose "Yes" for the "Change geometry of target feature to geometry of join feature" parameter. The goal of this join is to join the point data with the polyline closest to it using the field calculated by Calculate Distance. We choose to change the geometry to the geometry of the nearest polyline feature for use in the following Calculate Fields tool.

Our last step is to use a Calculate Fields tool (Add field calculation >Geometry) to create a polyline between each point feature and the nearest coordinate from the polyline data source. I achieve this by using PointToCoordinate in ArcGIS Arcade. As a note, before this Calculate Field tool, I opted to add a Project tool after Join Features to change my spatial reference from 102100 to 4326.

My final real-time analytic looks as follows:

In the screenshot below, the blue polylines are the output of the real-time analytic above. The polylines connect the simulated storm data (blue points) to the nearest point along the polyline feature class (purple lines).

If we were interested in drawing polylines between point features and the nearest coordinate on a polygon instead, we could use the same workflow with the exception of slightly editing the Arcade expression in the Calculate Fields tool to use NearestCoordinate instead.

After using this workflow, I am able to successfully create a polyline feature class (blue) that connects my simulated storm point data (blue) to the nearest coordinate on a polygon buffer that has a 5 mile radius around major US cities.

I hope this is helpful - let me know if you have any questions!