The trip mileage displayed in DAT load boards may be different than the mileage displayed in ALK maps (PC Miler).

How mileage look-ups work?

DAT downloads the latest version of ALK's mileage each year.  When users of DAT load boards are being provided mileage, it is coming from the downloaded version hosted at DAT, not from a direct lookup to ALK.

How can mileage be different?

ALK continues to update their mileage throughout the year, adding more city combinations and refining mileage that needs to be updated.  While their database is being updated, DAT's downloaded "clone" of it is not.  DAT's sync schedule with ALK is yearly.

This means that someone comparing the mileage in DAT's load boards and directly with the most recent version of ALK could see a difference in mileage until the next yearly sync occurs.

Note: In PC*MILER, distances are calculated by identifying the roads a vehicle will take between two points and summing the distances of each road section to determine total mileage, similar to using an atlas.
Routes adjust to the nearest truck-usable road on the highway or local street network. This local distance is the straight-line distance from the plotted point on the map to the closest truck-usable road.