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Map off??

Started by Warnberg, January 19, 2012, 12:28:01 PM

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Great site guys, I have a question... I downloaded the Florida Topo just to play with, I had to add the my trails software to get it to install correctly on windows 7 64 bit... anyway what I have found is the roads and the map are all off... way off actually.. anyone else seeing this?  I did a birds eye of my neighborhood with the roads then looked at the topo.. roads are not even close....

Anyone else see this?



How far off is WAY off?  Some places can be dead on and some can be 200 feet off.  The maps are based on Census Bureau Tiger files (the only free source for the US.)  They aren't always up to date, especially with recently added developments and depending on when the map was compiled the accuracy of road alignment will vary.


This thread really needs a screen shot to illustrate what you are seeing ;-)

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Quote from: babj615 on January 19, 2012, 04:50:21 PM
This thread really needs a screen shot to illustrate what you are seeing ;-)
Track offset parallel to road would help.  I've experienced a 180 foot offset on maps of mine.


ok, lets see if this works.... first shot is just with the normal map, not birds eye image overlay, second shot is birds eye overlay with Florida TOPO, last shot is birds eye with normal map...

word doc attached with screen shots

Sorry had to drop the first image to get under the file size limit


Its clearly a data error.  All maps have them.  Generally they are right 99% of the time.

However, TIGER census data always appears to be slightly off- 25-50 feet.  If you compare City Navigator to census data, the roads will normally not match up perfectly.  And its the census data that is normally off.  If you field check the differences or use GoogleEarth, it will show CN is normally correct.  I suspect the tiger data is just not draw to the same degree of accuracy.  Its intended for paper maps for census enumarators-not for use in a GPS.  So they don't need to draw the data in as high of resolution as a GPS can detect.

But what you are showing is not an accuracy issue, it is a bad data issue.


With the new roads data out from the Census the Florida map is due for an update. Maybe that will fix it.
Dan Blomberg
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