Posted on 30-May-2005 23:25 by Peter Torr Smith|
Filed under: Reviews
This month I had the opportunity look at 3 GPS units from www.efrontier.co.nz. Intergen was hosting this month’s Windows Mobile User Group in Wellington, and for it had put up some great spot prizes, including the GlobalSat SD-501 SDIO GPS receiver. eFrontier also lent me demo units of the Leadtek 9534 Compact Flash GPS receiver and the latest GlobalSat Bluetooth GPS receiver, the BT-338. All three utilise GPS Chipsets from www.sirf.com, though each use a different one.
Although the SD-501 was being put up as a prize, I had a short period beforehand to give it a quick “quality check”, and the winner kindly lent me the unit again to complete my review. This is quite a cool looking unit with a fold up main antenna that the manufacturers describe as a high sensitivity active type. It comes with a clip-on booster antenna, and eFrontier shipped this model with an additional magnetic plug-in antenna on a good length extension cable which could be used instead. A pouch to hold all the bits was also included.
At first it looked a bit flimsy, but it felt strong enough once plugged in, though I wouldn’t recommend it for rough environments which may better suit a compact flash or Bluetooth unit. This one is ideally suited for in-car or in-boat navigation, or getting a sample of waypoint location measurements out in the field, and then putting it back safely into its pouch.
Being able to attach the main booster antenna gives marginally better reception, and though it seemed a bit fiddly, it clipped on quite firmly. The magnetic-base extension antenna could be a bit more useful as it could for example be put on the dashboard or roof of a car or boat for better reception. The unit has an LED on the top indicating connectivity and fix status (this one was red, not green as shown).
SD-501 with booster antenna
The SD-501 utilises the SiRF Star II/X-Trac chipset arrangement and consumes about 90mA of power, about a third of that used by the WiFi on my iPaq. Whilst the SiRFStarII chipset has been around for several years, the newer X-Trac technology enhancement uses advanced algorithms to utilise extra weak sattelite signals alongside the strongest signals to calculate a more accurate position. This process however can introduce a slight delay which at high speeds could be a problem for street navigation applications. It is also reported to “overshoot”, or report a still moving position for a short while when one stops moving.
I could track my walk to into the urban canyon of The Terrace in Wellington. On the way home however, obtaining an initial fix surrounded by tall buildings took several minutes. That night I managed to track eight (yes eight!!) sattelites, and get a fix fairly quickly on my location and height from inside my dining room (albeit through a tin roof and wooden walls). Not bad at all.
I did a short road-test with it through the Wellington CBD, and it tracked me pretty well through the concrete jungle. It did lose its fix a couple of times, and as such did not live up to the standard set by its Bluetooth big brother the BT-338, however it wasn’t bad at all.
My walk to work into the urban canyon of The Terrace
The SD-501 tracking pretty tightly during a slow trip through the after work traffic
One issue I have with SD & SDIO in general, at least on the HP iPAQ models I’ve use, is the ease at which the card or device can be nudged and then “spring” loose of the slot. This means it can lose its connection or fall out easier than with a CF slot. This and the delicacy of the SDIO connector was really my only negative experience.
Beware, not all PDAs with SD ports support the SDIO interface. I use an HP iPAQ hx4700, which has both CF and SDIO slots, but my old Compaq iPAQ 3860 wouldn’t acknowledge the SDIO device.
It came with a mini CD with PDF manuals, and a very basic GPS application to read location, speed, direction, and sattelite signal strength details. However eFrontier give with all their GPS units a free copy of GPSWizard, a well featured non-map GPS application which, though at times a bit unstable, allowed me to begin my evaluation of the hardware.
Overall, a fairly sensitive and low power unit that, with the X-Trac enhanced chipset, works work well in poor signal environments. A bit delicate for my likings, but that is not specific to this GPS unit but to SDIO devices in general.
Small profile with fold-away antenna.
Useful for many PDAs that only have SD
Very sensitive with X-Trac.
External antenna connector
Booster antenna included
Low power consumption
No need to keep charged; uses host power.
Programmable & configurable chip.
SD connector in general “not so strong” and doesn’t grip firmly.
Uses up SD slot which may be required for a memory card.
No onboard memory.
No onboard battery to “keep alive”
Using host power reduces operational time.