GPS Inaccuraccy

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07-31-07, 09:50 PM

#16

Lil4X

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Location: Houston, Republic of Texas

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Quote:

Originally Posted by Rockville1

Ok, I think I see the issue. It seems that those complaining about inaccuracy are basing this on the Lexus' Nav system telling them that they have arrived at their location when they are about 300 feet or 1 block away from the actual destination.

Quote:

Originally Posted by silvervett

All the GPS units get my position dead on but get the street number wrong.

The mapping software is produced by cartographers who routinely take position data from aerial maps, but can only rely on existing maps for street numbers. Some cities (Houston being one) have rather odd numbering errors that result from stitching unincorporated areas into the city over time.

In Houston, northbound on Hillcroft, you cross Harwin, a set of railroad tracks and your next cross street is Richmond. You have traveled two blocks, but the street address jumps nearly 40 blocks. GPS doesn't have that level of local knowledge to anticipate this and will doggedly try to place you back on the railroad tracks if you have been so unfortunate as to program an address that falls between two known points. It doesn't know that this address does not exist. There are any number of what appear to be errors that are actually on the map discs. That's why we have updates. SOMEDAY we hope the map-makers will resolve all of them. Don't hold your breath.

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07-31-07, 10:22 PM

#17

silvervett

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Quote:

Originally Posted by Lil4X

I believe you've found the answer, Rockville! the Lexus audio announcement is intentially set to lead the actual position by as much as 300 feet to allow the user to see the actual location and make preparations to stop . . . then there are a couple of other considerations:
The mapping software is produced by cartographers who routinely take position data from aerial maps, but can only rely on existing maps for street numbers. Some cities (Houston being one) have rather odd numbering errors that result from stitching unincorporated areas into the city over time.

In Houston, northbound on Hillcroft, you cross Harwin, a set of railroad tracks and your next cross street is Richmond. You have traveled two blocks, but the street address jumps nearly 40 blocks. GPS doesn't have that level of local knowledge to anticipate this and will doggedly try to place you back on the railroad tracks if you have been so unfortunate as to program an address that falls between two known points. It doesn't know that this address does not exist. There are any number of what appear to be errors that are actually on the map discs. That's why we have updates. SOMEDAY we hope the map-makers will resolve all of them. Don't hold your breath.

I had a house 40~0 miles north of Houston in the Walden development of Lake Conroe and that house number was dead on, My house number in Hauppauge LI NY is also dead on. But the number of my mothers house in Huntington LI NY is way off, her house number is 23 but the GPS shows it as 87 and the funny thing is that the highest number on the street is only 25. The house I am buying in Anderson SC is on a road that is a big circle. The number of my future house is 4026 but when I locate it on the GPS or the Google map 4026 is on the opposite side of the circle. So I think the question is does the GPS put you in the correct location (in other words if you are at the corner of main street and 1st ave does the GPS show your position as being located at the corner but maybe the house number you are in front of is not correct?) but the street number is not correct? If that is the case the GPS is working the way it should and the maps for the city you are in are not numbered correctly.