Why is my GPS for truck not working since I have charged my truck batteries?

Now a days gps technology is gaining popularity in cars and trucks for proper navigation purpose but some problems still exist in technology. The biggest problem is in the blockage of electromagnetic signal transmission by obstacles such as mountains or high buildings long tunnels or urban canyons moreover thick branched trees. So multipaTH signals are generated by reflections from nearby surfaces or ground but it can also interfere with the gps data. Some methods have been introduced to improve these disadvantages. Dead Reckoning is an advanced technology or way to keep tracking vehicles during periods of blocked transmission of signals. Basically DR system is used to improve accuracy when GPS transmission is available in addition to being a backup information when transmission is totally blocked. However, its accuracy tends to drop if the car travels for an extended or long period without receiving any kind of electromagnetic or GPS signal. Thanks