In reply to echo34:
It can't download ephemeris & almanac info from the web like a phone can (AGPS), so a cold start will take much longer; up to 12.5 minutes to acquire the slow, rotating drip feed from the constellation. But once acquired, it should give a fix as quickly as a phone. Just keep it turned on for 13 minutes every four hours...
Your phone probably has a multi-system receiver, able to use GPS, GLONASS, Beidou and Galileo. So more likely to be able to see enough satellites to get a fix. IIRC, the Satmap has a SIRFStar 3 chip; good, but GPS only.
I'd also check the battery life if it's lithium.