GPS for Dummies.pdf - Engineering Surveyor

Chapter 5: Selecting and Getting Started with a GPS Receiver93Type Rechargeable? Plus MinusNickel metal- Yes NiMH batteries are Depending on thehydride (NiMH) much better than Ni- milliampere capac-Cads because they ity (usually thehave a longer life higher the better),(although not as long can cost a bit moreas alkalines), don’t than lithium battersufferfrom memory ies. Have to buy aproblems, can be re- charger.charged up to around1,000 times, and arereusable.Rechargeable Yes Usually last about one- Cost roughly thealkaline Have to buy a charger. same as NiMHs buthalf to two-thirds as aren’t as popular.long as regular alkalinebatteries and are rechargeableup to100 times.Expect to pay about $4 for a four-pack of alkalines (the more you buy in asingle pack, the cheaper they are) and about $15 for NiMH. Chargers can runyou anywhere from $20–$50. (Some chargers come bundled with a set or twoof batteries.) When it comes to batteries and chargers, online prices arealmost always cheaper than full retail, so be sure to shop around.Some GPS receivers have a battery saver modethat can greatly extend the life of your batteries.(Check your user manual to see whether yourmodel has this feature and how to turn it on.)Normally, a GPS receiver processes satellitedata every second and determines your speedand location. Based on this information, the GPSreceiver predicts where you should be the nexttime it gets satellite data. If the prediction is closeto your actual position and battery saver modeis turned on, the GPS receiver will start receivingsatellite signals every five seconds or soinstead of every second. In addition, some of theBattery saver modeinternal electronics are turned off during this waitperiod. Because a reduced amount of power isneeded, the battery life is extended.The GPS receiver continues to access satellitedata every five seconds until the predicted locationisn’t accurate anymore, at which time itswitches back to receiving data every second,starting the process over again. (Some GPSreceivers provide you with a number of choicesof how often satellite data is received. Themore seconds, the more battery efficient thereceiver is.)