Map Data Accuracy

The following are sample maps made using sdts2mp and GPSMapEdit.

I used 3 different data sources: USGS 24K DLG Benicia, USGS 24K Napa, and US Census Bureau Tiger Line Data. I compared them to each other and a GPS track I made while riding my bike around town.

Data Source	Screen Shot
USGS 24K DLG and GPS Track (shown in red)
The GPS track follows the road pretty closely and there is a lot of detail in the map. Only the main freeways have names.

Data Source	Screen Shot
USGS 100 K DLG and GPS Track (shown in red)
The GPS Track is still close to the roads. There are fewer street types (no more thicker main streets in town.) There are fewer water types (no more tidal flats.) The accuracy of the roads and coastline is worse. Notice how the coastline is smoother and the downtown streets are not quite square anymore. The main freeways are still the only roads with names.

Data Source	Screen Shot
US Census Bureau Tiger Line Data and GPS track (shown in red)
The Streets are a little farther off from the GPS Track. The straight lines downtown are now gone and smooth curves are more jagged. The coastline is crude and inaccurate. The TIGER data has street names and lake names. All streets are shown as one type, but it is possible to import the road types using excel to edit the shape file.