Why doesn't Map Center mark the right house on the Air Photo when it finds my address?

Map Center uses a strategy called geocoding to take a written address (like 1025 2nd Ave) and locate it on a map. Geocoding usually does find the right block for your address, but it usually does not find the exact location along the block when marking your address.

Here's why:   Map Center knows the starting and ending addresses on each side of every street block in Oakland, but doesn't know exactly where each house is along the block. So, when Map Center marks your address along the block, it uses interpolation. With interpolation, Map Center divides up the street evenly between the starting and ending addresses and marks your address at the right division point. For instance, on an imaginary street with only three addresses (#1, #2, and #3), Map Center would divide up the street into three points. If your address was #2, Map Center would place the mark for #2 in the middle of the block, even though the house with address #2 isn't exactly in the middle of the block. Because most houses are not evenly distributed along their blocks, Map Center's mark may not match your house's actual location in the air photo.

Using a real example, one of the blocks of Whittle Avenue starts with the addresses 3900 and 3901 and ends with the addresses 4098 and 4099. When you ask to see the location of 4007 Whittle Avenue, Map Center first figures out that your address is odd, not even, and so it will be on the North side of Whittle Avenue. Then Map Center interpolates the location of 4007 and marks this interpolated spot on the map.

As you can see from the air photo, Map Center's interpolated guess about the location of 4007 Whittle Avenue does not match the real location of the house at 4007 Whittle Avenue. Geocoding is a useful tool for finding the approximate location of an address, not the exact location of a house.

Frequently Asked Questions:

1. Where did the map data come from?
2. How do these interactive internet maps work?
3. Why doesn't Map Center mark the right house on the Air Photo when it finds my address?
4. How many maps have these sites created?
5. Why do Map Center maps have a different look and feel from other internet maps?

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