Add station.md to labeling expressions

Adds an example of labeling stations and vertices with measure
values along pipelines.

labeling/station.md

@@ -0,0 +1,68 @@
+# Station Labels
+
+ArcGIS Arcade is a simple scripting language that can be used across ArcGIS. Arcade Expressions can be used to generate symbology, pop-ups, labels, and more and are supported in ArcGIS Pro, web maps, and mobile applications. Here we will look at using Arcade Expression when working with linear referencing pipeline asset data.
+
+## Use cases
+
+Labeling stations and vertices with measure values along pipelines.
+
+## Workflow
+
+Copy and paste the expression found in the expression template below to the Arcade editor in ArcGIS Online, the relevant location in ArcGIS Pro, or the relevant location in a custom app.
+
+### Watch this YouTube video for a detailed workflow example
+
+[![A thumbnail of the Using ArcGIS Arcade expressions with linear referencing data YouTube video](./images/station-youtube-thumbnail.png)](https://www.youtube.com/watch?v=VYjkEofjsxI 'Using ArcGIS Arcade expressions with linear referencing data')
+
+## Expression Template
+
+This arcade expression will return a formatted string for use in labeling stationing along a pipeline. Stationing specifies the relative point along any reference line.
+
+```js
+// Stationing specifies the relative point along any reference line
+//US Survey Foot - 1 station = 100.0' = 1+00.0
+//Metric - 1 station = 1000.0m = 1+000.0
+
+var station = $feature.MEASURE
+
+var IsNegative = 0 //tracks +/- values
+var Type = 'Feet' //"Meters" Switch type as needed
+
+if (station < 0) {
+  //convert all negative stations to positive and append back the - at the end
+  station = station * -1
+  IsNegative = 1
+}
+
+//##00+00.0 or ##0+000.0 - These functions will provide this format regardless the length of the field
+//formatting with decimals after the + sign - if there is not
+
+if (Type == 'Feet') var StationlbR = Text(station, '00.0')
+if (Type == 'Meters') var StationlbR = Text(station, '000.0')
+
+//Getting rid of the two initial character dividing by 100 or 1000. formatting result with 2 zeros and room for more characters
+//using the Split function to extract from the second character from the left of the decimal point
+if (Type == 'Feet')
+  var StationlbL = Text(First(Split(station / 100, '.', 1)), '###00')
+if (Type == 'Meters')
+  var StationlbL = Text(First(Split(station / 1000, '.', 1)), '###000')
+
+var Stationlb = Concatenate([StationlbL, StationlbR], '+')
+if (IsNegative == 1) Stationlb = '-' + Stationlb
+
+return Stationlb
+```
+
+## Example output
+
+### Event Editor
+
+![Event Editor](./images/station-event-editor.png)
+
+### Web Map
+
+![Web Map](./images/station-web-map.png)
+
+### Mobile
+
+![Mobile](./images/station-mobile.png)