receivers in the vicinity of the relevant ground station can use this correction to improve their own positioning solution.
Because mobile receivers in the vicinity of the ground station are receiving the same GPS satellites through essentially the same part of the atmosphere and at the same instant as the known ground station, these differential corrections are quite effective at overcoming the effects of the above-mentioned two categories of errors. Because the mobile GPS receiver is not at exactly the same coordinates as the ground station and the true programmed position of the ground station may not be perfect, however, the correction achieved by DGPS-type techniques is consequently not perfect as well. In addition, the DGPS receivers are more complex, and therefore more expensive, than ordinary GPS receivers.
In thejudgment owed by the joint tort-feasors McBroom and Ernst, in that State Farm made the payment as the contractually obligated insurer under the appellant's policy of insurance and not as a joint tort-feasor under the judgment.
We affirm.


*133 Facts
On October 18, 1996, the appellant was driving north on Interstate 35 in Kansas City, Jackson County, Missouri. As she approached the Paseo Bridge, a vehicle ahead of her, the phantom vehicle, slowed or came to a stop on the highway, causing her to slow. As she did, the vehicles being driven by McBroom and Ernst collided with her vehicle, causing her injuries.
On July 14, 1997, the appellant and her husband, Steven Gaunt, filed a two-count petition for damages in the Circuit Court of Jackson County against McBroom, Ernst, and State