This is the gps data logger that I designed just recently. I just got the first one assembled. The EM406 gps uses the latest SIRFSTAR III chipset to make sure you get a signal in areas of dense foliage, canyons, and even inside buildings depending on the construction technique. Battery is a 3.6V lithium ion type large enough to provide 8 hours of continuous operation and can be replaced with a fresh battery or charged/powered via a usb port at 100mA. The SD memory card can be as large as 2GB and up to 255 files can be on the card at a time. The time and date of each file is also recorded when the file is created and updated. Recording options allow for direct recording of NMEA output from the gps or processed data. Either option is configurable via a CONFIG.TXT file.