GPS Receivers – which style for my PDA?

This article describes the form factors available for GPS receivers which are going to be used as an add-on to a PDA such as an IPAQ and XDA for example.

GPS (Global Positioning System) use is increasing world-wide – and with good reason, it is an excellent tool for determining your position just about anywhere on Earth. When combined with software it is possible to pinpoint your position on a map via a computer or PDA.  With the correct kind of software you can enter an address and the software will calculate a route complete with turn by turn voice directions.  Newer and upcoming versions will also include traffic reports, local speed restrictions such as school speed limits and so on. Most of the current versions also included fixed speed and red light cameras.

To make use of the GPS there are two requirements, firstly a GPS receiver and secondly a Computer (in this case your PDA) to display the information and show your position. This article focuses on the receiver side of things.

What the GPS receiver does

The GPS receiver is actually a fairly complex computer in its own right. It receives signals from a grid of satellites orbiting the Earth and translates that data into something meaningful which can be used to determine the position of the receiver on a map. The actual mechanics of this is quite complex and is beyond the scope of this article but if you are interested there are many excellent web sites that explain how all this is accomplished – but be prepared for some heavy maths!

Form factor

Basically there are four different styles of receivers suitable for PDA use. Each has its own limitations and advantages, and not all are suitable for specific PDA’s. The following is a brief description of each along with their advantages/disadvantages and limitations.

Bluetooth
I think it’s fair to say that the Bluetooth GPS receiver is the most popular for PDA use.

Advantages  

*   Can be placed in an optimum position for signal receiving
*   Does not use power from the PDA – has its own battery
*   No wires – less clutter

Disadvantages  

*   Another piece of equipment to carry around
*   Needs to be charged separately
*   Easily forgotten – resulting in battery discharge
*   Requires a Bluetooth enabled PDA – although most PDA's are nowadays
*   Generally the most expensive option

Compact Flash - SD Card
These units plug into the compact flash or SD card port on PDA’s 

Advantages  

*   All in one – no additional bits to carry around
*   No wires – less clutter

Disadvantages

*   Limits the placement of the GPS – you need to see the screen
*   Appear to be fragile
*   Uses power from the PDA – shortens battery life
*   Increases the size of the PDA
*   Limits the use if away from a power source
*   SD card types don’t have memory so its use for large mapping data is very limited

Mouse Type
These units have a GPS receiver at the end of a RS232 or USB  cable. They are really only of use (in PDA terms) when used with a appropriate Car mount that has a port built in specifically for the GPS – Specific Arkon mounts for example

Advantages  

*   The cheapest option
*   Good if you plan to use a Notebook as well as your PDA – saves buying two GPS receivers
*   Most have magnetic bases for putting onto a car roof for example

Disadvantages 

*   Wires – more clutter
*   Can only be used with the mount – therefore use away from a car is limited to a notebook

Sleeve Type
These units are designed specifically for certain IPAQ models and fit around the PDA like a backpack

Advantages  

*   All in one solution – less clutter
*   Most models have additional expandability (additional storage for example)

Disadvantages

*   Makes the device bigger
*   Limits placement of the receiver
*   Uses the PDA battery when not connected to a power supply

*   Device specific - only suitable for certain IPAQ's