I read somewhere that the tracking device feeds a signal to the satellite every fifteen minutes (4 times per hour) and records that exact moment -- so the speed might show 0 if the team is at a temporary, momentary stop. The feeds are not coordinated, so each team is feeding data on a different schedule -- hence they seem to be jumping the lead, when they are probably all really running pretty smoothly. After the teams get all spread out in a day or so it should give us a really good feel for the race,
among these fifteen teams. Remember there are 80 or so teams that are not carrying the device, and one or two or three of them may in fact be in front or well up toward the front.
This is a GREAT toy for us spectators, but the mushers might not like it when it's all said and done.
txbennett