LAPTOPS (Windows 2000 / 98 / 95 / ME / NT / XP)
Laptop computers are more fragile than Pocket Computers. Batteries only last several hours, and vehicle power is usually required.  Laptop's main failures are broken hinges, disk drive failure, and electrical contact fatigue (discussed later).   There are ruggedized Laptops for $3000 up,  however it has been our experience that ruggedized PC's disks fail at a high rate in the field.

PocketPC Computers (and Windows CE) 
Batteries last longer than Laptop computers. Color displays vary widely. Some color screens are easier to see out of direct sunlight, while others are easier to see in direct sunlight.   Black-and-White and Gray-Scale displays are visible in direct sunlight.  Handhelds typically have 32-64 Mbytes of RAM. They can hold one day to a weeks data and maps. 

We recommend using a Flash card to backup your data.  Flash cards can also be read by your desktop computer (using an optional card reader).  A rule of thumb is to backup your data whenever you have more data in memory than you are willing to lose.  We recommend backing up data from the computer to the Flash card at least twice a day.

Pocket computers are more reliable because they have no hinges, no disk drive, and fewer internal electrical contacts.  Because the screen is smaller, more time may be spent opening, moving, and closing screens if a lot of interaction is required. 

Ruggedized PocketPC Computers
There are several ruggedized Pocket PC Computers on the Market.  The TDS Ranger and Juniper Systems Allegro are two.  The price runs US$2000 - US$3000, however these machines are more rugged than ruggedized laptop computers.

BATTERIES
Always keep good batteries in the portable computer even though you are running on vehicle power, because just starting the engine can interrupt power momentarily.  When you turn the switch to start the engine, the computer may shut-off or even lose its memory if it has bad batteries.  Computers with main and backup batteries do not recharge the backup battery.  If the computer lays around with the main battery dead, it will discharge the backup battery.   Then its memory, programs, and data will all be lost. 

COMPUTER CARE
A main failure of field computers is accident. They are dropped, run over, or get their hinges broken, etc.  Just as important is electrical contact fatigue. If a computer is vibrated regularly, even when not in use, it will fail because the electrical contacts wear out. Obtain a soft lined case for transporting the computer.  Do not leave the case of the computer in direct mechanical contact with a vehicle where it can pick up vibrations.  If the computer is permanently mounted in a vehicle, shock mount it.  Its life will be greatly extended. 

COMPUTER DON'TS 
Do not make a direct connection to a vehicle charging system (12 volts) without the appropriate power adapter, even if the computer takes 12-15 volts on its power input.  Also, do not connect SensorTrack ^tm  inputs directly to 12 volts without protective series resistors and fuses. The charging system can see 35 volts or higher when jump starting vehicles, and this is enough to damage the sensitive computer if unprotected. 

Humidity and salt are not the computer's friend. Computers can be slightly moisture resistant, though. We put a Zip-Loc bag over the computer to block moisture, and use the stylus right through the bag.  If the computer could be damp on the inside at the end of the day, backup the memory, remove the main and backup batteries, and leave the computer in a low humidity area for a day or so.  Salt spray should not be allowed to get on the computer. If it does, it should be wiped off with a fresh water dampened cloth to prevent salt from getting inside.  Salt is another enemy of electrical contacts.