III - III Plus Maps

First off, I apologize for fixing the screen width so wide. As I was playing with the page layout, I decided that I preferred a fixed layout for the screen dumps over more readable text. This page is graphically intensive and will take about three minutes to download with a 28.8kbps connection.

Here is a comparison of the screen displays on the Garmin GPS III Plus (software revision 2.01) with MapSource U.S. Roads & Recreation, MapSource WorldMap, Base III Plus, GPS III (software revision 2.07) & StreetPilot (software revision 2.04) with Dallas/Fort Worth MapSource MetroGuide. For complete details on the data included with each MapSource map, visit our MapSource comparison.

This is centering on our house, which is 4.9 miles at a bearing of 228 degrees from the Dallas/Ft. Worth International Airport Tower located at N 32° 53.815' W 097° 02.548'.

The GPS III Plus was set to display "Most" detail and "Normal" detail, all data elements were set to "Auto", with the exception of waypoints, which were set to 1.2 miles and street labels which were set to 500 feet. The GPS III had all data elements set to 500 miles, with the exception of waypoints, which were set to be the same as the GPS III Plus. The StreetPilot does not have the same programming flexibility as the GPS III series, so it was set to the level I call "More," which is one notch less than full. All devices were set to simulate mode to remove Selective Availability drift and to make the EPE circles comparable.

I used G7TO to create the screen dumps.

I have placed a Mapquest map of the same area at the bottom of the page for comparison.

This is the tightest zoom level and all devices have the overzoom indicator lit. This indicates that the map is being displayed at a higher resolution than it's designed for and plotted objects such as roads and rivers are being extrapolated for display. MapSource provides less granular data -- you can see this because of the Estimated Predicted Error (EPE) & Map Accuracy circle. The circle is still off the display on the other two devices. For comparison, the display off to the right shows the effect of EPE without Map Accuracy. I turned off the base map and MapSource map on the III Plus to get this display.

The GPS III display is gray because it is displaying Metro Areas. I have not been able to make the GPS III Plus display metro areas. Note that the WorldMap Map Accuracy circle is slightly larger than the U.S. Roads & Recreation map. I believe this is because the WorldMap data is slightly more granular (800 ft. maximum zoom compared to 500 ft.).

U. S. Roads & Recreation		WorldMap	GPS III Plus	GPS III	StreetPilot w/ MapSource
Most	Normal	More	Base	Base	More

At this level, you can see a stream runs just to the west of the house. Unfortunately my neighborhood is not included on the MapSource CD. We weren't included on Street Atlas 5, but we are on Street Atlas 6, which indicates that we're a fairly recent addition to the TIGER database. We are, however, on the ETAK database that is used for the MetroGuide. But our house is on the other side of Bonham Trail, which I believe is an error in the mapping data. Also notice that MetroGuide is out of overzoom mode already. That's one level less than the best level available on the GPS III Plus.

This is the first level where MapSource does not have the overzoom indicator lit. The other two devices begin to display the EPE circle, indicating the higher granularity of their base maps. If you were to turn off the maps at this level, the EPE circle would look comparable to the MapSource device.

You can begin to see a highway to the south and streets to the north and west of my neighborhood. The MetroGuide correctly indicates that 114 is a divided highway.

At this level, MapSource is showing other neighborhoods and the other two show a single line to the south reflecting the highway. Note that the WorldMap is providing some additional detail to Highway 114, but not as much as U. S. Roads & Recreation.

At this level, you can begin to see that the III Plus has updated its highway display mode, using a double line to reflect the divided highway. The MapSource Normal mode has started to exclude street detail. More importantly, Normal mode has started to replace MapSource data with its internal base map! If you look carefully, you can see that there's an EPE circle that's not on the Most level. This is an indicator of the higher granularity of the data being used.

The waypoint marked GRAPE visible on the MapSource and III Plus is a National Geodetic Survey marker located at N 32° 55.858' W 97° 05.690'. Lake Grapevine is beginning to become visible to the northwest.

Interestingly, it appears that the III has better resolution on the lake than the III Plus. The high amount of clutter displayed on the MapSource near the lake is a large number of parks and boat landings. WorldMap is not providing the same level of detail that you seen on the coastline of the U. S. Roads & Recreation, but it is better than the base map (almost the same as the GPS III). Also note that the MetroGuide lake detail is much higher than any of the other databases and has similar coastal detail to the R & R.

The icon for DFW airport is visible to the southeast. WorldMap has included an airfield at Keller, but I believe that's also available otherwise. Too much detail on the other screens to show it.

At this level all three devices have the overzoom indicator dim, so map accuracy should be comparable on all three. To the northeast, you can see I35-E. The dots on the road reflect exits. If you move the cursor on top of the dot, you'll get a list of services at that exit. Here is also where MapSource normal mode starts to have a significant impact in reducing screen clutter. It appears to be the same as the GPS III Plus at this point.

The hatch marks on the MapSource display indicate that I have not uploaded the detailed maps for that area. That's the southern portion of Tarrant County to the south and Collin County to the east.

MapSource and III Plus displays are almost identical at this point, but you can begin to see the light gray MapSource detail lines (look just to the right of Bridgeport). Another interesting difference between Most and Normal mode can be seen here. Look at Denton & Plano. In Normal mode, they're printed in small type, even though they're fairly large towns. In Most mode, they're displayed correctly, but do eat up lots more screen.

You can see that there are more roads on the III Plus, but lots of the tows that you see on the Plus are also on the III -- it just won't allow the screen to get as cluttered as the III at this setting.

The III plus is displaying icons for rest areas (man/woman) and welcome centers (question mark) on the Interstates.

MapSource normal mode appears to be a little too stark at this point -- it's almost exactly the same as the GPS III. Notice at this point, it's the GPS III that has the wide highway lines. As the WorldMap zooms out, you can see the crosshatch begin. It's troubling that it continues all the way out to the 300 mi. resolution, as it doesn't appear to be displaying any MapSource data.