There is an odd symbol, like a plus sign with a flag on one arm, or a
swastika with three of the end flags taken off.  It looks a little
like a number four with an open top.  I see it painted on the pavement
in intersections in white paint, maybe four(?) feet to a side.  My
question is: What is this marking painted on the road for?  Does it
indicate something like utilities under the road?  A friend who is an
engineer thought it might be for aligning aerial photgraphs (aerial
photgraph "register" or "registration" marks), but I couldn't find any
corroborating evidence for this.  I live in Minnesota, but I have been
told that other cities also have these marks.

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Request for Question Clarification by czh-ga on 27 May 2005 04:12 PDT

Hello vinceclortho-ga,

Where are you located? Where have you seen these pavement markings?
(Street, City, State) Thanks.

~ czh ~

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Clarification of Question by vinceclortho-ga on 31 May 2005 14:07 PDT

The marks are found in Minneapolis.  I don't see them in St. Paul or
the suburbs, but I don't spend time in other Hennepin County suburbs. 
Each "arm" is about 3.5 or 4 feet in length from the center of the
figure, and the propostions are roughly squarish.  They almost always
appear in four-way intersections with stoplights, but I have found one
that is in a three-way intersection with no stoplight (on Portland
Avenue near Diamond Lake).

At the intersection of the arms is a metal plate or cap about eight
inches across.  The plates have no writing on them, but they do have
small indentations with a bar across them that look like someplace to
attach a hook or rope or carabiner or something.

Here is my attempt at drawing the symbol.  I used a letter "Oh" for
the metal disk/plate/cap in the center.  It is painted in white paint
the same width as the lines use to mark lanes.


            ------------
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 -----------O-----------
            |
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            |
            |
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            |

Thanks!