Wednesday, September 1, 2004
Garmin GPSmap 296
Terrain comes to portable GPS
The full-page display shows red terrain ahead (zero to 100 feet clearance), and if you fly too close to higher ground, a separate terrain-alert square pops up at the lower left screen to emphasize the danger. Proximity alerts are pilot selectable at 60, 90 and 120 seconds. Increase your altitude as you approach the obstacles, and the terrain gradually changes color from red to yellow (500 to 1,000 feet clearance) when you climb slightly above it, and finally to black when you’re well clear of the obstacle.
Such capability demands an awesome terrain database, and that describes the one included in the 296. Garmin aviation marketing manager Tim Casey said that the new geographical database now includes something like 30 million data points, roughly one for every 30 arc seconds of lat/long. That represents one data point each for 30 million geographic boxes roughly a half-mile on a side all over the U.S.
The 296, however, doesn’t have any trouble keeping up with all that data. At 200 mHz, the Garmin 296’s processor speed is almost triple that of the 196 introduced two years ago at the EAA AirVenture, so the new unit redraws map terrain at a much faster rate. (In fact, Garmin’s in-house database includes data points down to one arc second, but the processor necessary to draw a map to such tolerances in real time—
one every 100 feet—would have to be awesome.)
The pseudo instrument page is similar to the one on the 196, and it’s just as capable, but the tripled processor speed won’t have much effect on instrument readouts. The horizontal- and vertical-position refresh rate is limited by the frequency of GPS updates, one per second. Garmin incorporates the information seamlessly, so the needles move smoothly, but it’s important to remember there is a slight delay from control input to instrument indication.
Also, keep in mind that what looks like an artificial horizon at lower left isn’t intended as a replacement in case your attitude indicator develops a bad attitude. The instrument is a pseudo rate-of-turn indicator with no pitch information. The pseudo panel page offers instruments more as individual backups rather than for full-panel replacement. In the unlikely event that you lose altimeter, airspeed, VSI, HSI and turn coordinator plus all nav information at the same time, the 296 could theoretically serve as a backup, but only with very gentle inputs and in soft IFR.
The HSI Arc mode very well may be the most popular of the GPSmap 296’s electronic pages. It’s strictly a look-forward view that ignores everything behind you, but it still includes the key nav information in the corners. You can personalize the four corner readouts to your liking. Most pilots will opt for time and distance to waypoint plus speed and bearing, but there are a myriad of other options to suit your needs. Ranges are as you like them, selectable from a minuscule 20 feet to 800 nm.
Another improvement on the 296 is low power usage. A traditional complaint about portable GPSs since the early 1990s has been that battery life is sometimes very limited. The 296 features a rechargeable lithium-ion battery that’s alleged to run for 12 hours in ambient light, eight hours with backlighting activated. On airplanes fitted with a lighter outlet, you can use aircraft power to avoid draining the battery. That’s, by far, the best way to go, as you can select maximum backlighting without affecting battery life. Also, since the battery is rechargeable, you’ll be topping off the lithium-ion any time you’re using aircraft power. (Incidentally, don’t believe the readout of remaining battery time on the display. Timing the display suggested it was running down at about one minute for every 35 to 40 seconds of real time.)
Page 2 of 3