DOTS - Automatic Drill string Tally

All drilling operations rely on a correct drill pipe tally to control the position of the drill bit in the well. The pipe tally is the main source for measuring depths during drilling (also called "Drillers Depth") and represents the assembly of rotating parts that goes down the hole, which is a series of drill pipe connections and drill collars, ending in a rotating bit.
To confirm at any stage what depth the drill bit is operating at, the driller consults the pipe tally records, and measures the length of the current stand of drillpipe below the rig floor.

In practice, Driller's Depth measurement is mostly still a manual operation, not changed significantly over the years and there are many facets of the system with potential to introduce errors and inconsistencies. Since verification of ID's and lenghts have to be performed manually on the drilling deck, also the risk for injuries is imminent.

Potential operational errors due to manual tally management are:

 - a pipe section or stand has been left off the calculations
 - errors in manual registering of serial numbers during measuring, leading to wrong lenght for individual elements
 - additional downhole equipment has been added to the string without being accounted for
 - BHA is not correctly measured or recorded

These errors can become extremely expensive, and can lead to Non Productive Time of the rig or in worst case the loss of a well.