Hi Jarrett and Jim,
A bit late to the game on this one, but better late than never.
Yes, there is a reliable and accurate workflow to do exactly what you're trying to accomplish—and you're closer than you think.
To interpolate values like MP 64.02, 64.04, etc., between known mileposts (even when the real-world distances vary), the key is to convert your railroad centerline into a M-enabled route, calibrate it using your known milepost points, and then use linear referencing tools to generate and label features by milepost.
This approach mirrors how mileposts work on the ground—even if MP 64 to 65 is actually 1.3 miles long, it still counts as 1.0 milepost unit in the system.
✅ Step-by-step workflow:
1. Import your centerline into a M-enabled polyline feature class:
Create a new polyline feature class with M-values enabled.
Import your single, continuous railroad centerline into it.
No need to split the line at each milepost.
2. Use Calibrate Routes to assign milepost values:
Input your M-enabled centerline as the Route Feature.
Use your known milepost points as the calibration input.
Set Measure Calculation Method to Distance.
After this, your route will have M-values aligned with the milepost system—even if MP 64–65 spans 1.3 miles in the real world.
3. Generate interpolated points at fractional milepost values (e.g., 64.02, 64.04, …):
Since the Generate Points Along Lines tool uses spatial distance, not M-values, it won’t work for milepost-based spacing. Instead:
Create a simple table with:
Route ID
Measure (M-value) field — e.g., 64.00, 64.02, 64.04, … up to 65.00
Use the Make Route Event Layer tool:
Input your calibrated route and your table.
Set Event Type to POINT.
Use your Measure field to place each point at its exact M-value.
You’ll now have a dynamic layer of points at every 0.02 MP increment along the route.
Optionally, export this event layer to a permanent point feature class.
- This could also be accomplished using a Python script, without having to create the table.
4. Use Locate Features Along Routes to assign milepost values to other assets:
For example: road crossings, signal locations, etc.
This tool reads the calibrated route and assigns the appropriate MP value to each point feature based on its location along the route.
✅ Summary:
This workflow gives you an M-calibrated railroad centerline that matches legacy mileposts, allows precise placement of interpolated MP points like 64.02, and enables accurate milepost tagging for other features—even when physical distances between mileposts vary.
I hope this helps.
Best,
Cameron Rex
RMI Valuation
