Lat Long
I notice the big Goodsam book has lat & long coordinates for each RV park. In checking those with GPS systems that accept lat / long input that about 25% are incorrect. Where do these come from and wh...
Forum Discussion
cbshoestring wrote:
GPS not accurate. How is this news?
Come down my street and Garmin will say "now arriving at destination on left". I live on the right. :S
Go to my brother-in-laws...last thing Garmin says" You are now 5/10ths of a mile from your location". It knows where I am going, but can't provide directions there? Gets me a 1/2 mile away, knows I am a 1/2 mile away....just gives up????????????
A 25% error rate seems a bit high. My experience has been that GPS gets me there 95% of the time....gets me close 3%.....has no idea where I am going 2% of the time :h
Then again, I tend to imput addresses not coordinances. If you can't give me an address, I probably do not want to visit you.
The positional accuracy of a geocoded address depends on the base data. Google Maps does rooftop geocoding. When I geocode my home address in GM, it places the marker dead atop my house which sits 300 feet off the road.
However, many geocoding apps build their base lookup data from U.S. Census Bureau TIGER/Line shapefiles. These files include most of the street segments in the U.S. and have the left/right side beginning/ending house number ranges for each segment. Intermediate addresses are linearly prorated using those beginning/ending house number ranges which are not perfect. And addresses are not necessarily distributed uniformly along a street segment, so the location is going to be a bit off in many cases.
The concept of address geocoding is pretty simple, but the implementation is more art than science at times. (I wrote and support the geocoder for a large software company.)
