6' White "X" on the side of the roads

[Mossy Oak]

For several weeks now I have noticed white "X" made of cloth or plastic marking (4 to 6 feet in size) with a grade-stake in the center. I believe this is for aerial photography mapping purposes. Just wondering if anyone else has seen this on the side of the roads?

 

Could this mean new or better maps will be coming out I the future?

[iryshe]

My father works for DigitalGlobe, an imagery company. I asked a similar question and he said that there are companies that create these X marks with precise lat/lon coordinates so imagery taken from the air can be georeferenced correctly.

 

Jeremy

 

Jeremy Irish

Groundspeak - The Language of Location

[+LarsThorwald]

I actually used one as a reference point in our GO FLY ANOTHER KITE cache down here in Southern California. Had no idea what it was...

 

Charlie

 

"One should never begin a journey by heading in the wrong direction."

[+Rebel]

A couple of years ago here in Georgia several metro Atlanta counties painted big white arrows on suburban streets and rural highways. The arrows pointed to fire hydrants. They then used aerial photography to build a database of the location of every hydrant in the state.

 

Firetrucks use that database and can pinpoint hydrants very precisely.

 

Sounds pretty similar.

 

Oh, they also put little blue reflectors on the road near the arrows. At night the fire crews only need look for the blue reflection to find the hydrant.

 

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"If you tell the truth, you don't have to remember anything." - Mark Twain

[+True Grid]

Look in the center of the X and see if there is a surveyors nail there. These are used for aerial mapping. The surveyor provides the 3D coordinates of the X to the aerial mapping company who then does a fly over and takes pictures of the area. These points are then digitized into the photo and a computer generates an accurate topographic map, usually with contours, buildings, etc. Depending on the height of the flight, they can obtain elevation accuracy within .5 feet or better, on contours in open areas. Horizontal accuracy is closer yet.

 

"True Grid"

In the Pacific Northwet

[+VentureForth]

They're runways that are closed!

 

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Go! And don't be afraid to get a little wet!

[Mossy Oak]

quote:

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From True Grit: Look in the center of the X and see if there is a surveyors nail there.

---

 

I decided to check out the white X marks a little further. There is a marker in the center, a round flat plate imbedded into the ground about inch deep. The grade stakes has writing on them TMF GPS #100, I found 3 sites #100, #102 & #103

 

Thanks for all the replys. . .

[Mossy Oak]

quote:

---

From True Grit: Look in the center of the X and see if there is a surveyors nail there.

---

 

I decided to check out the white X marks a little further. There is a marker in the center, a round flat plate imbedded into the ground about inch deep. The grade stakes has writing on them TMF GPS #100, I found 3 sites #100, #102 & #103

 

Thanks for all the replys. . .

[+geomapper]

We had new monumentation set in our county several years ago when we started our program of developing a new digital base map for GIS. One lady call me complaiing about the white marker on the right-of-way in front of her house. She was certain it was causing her appliances to malfunction. Even after assuring these markers had nothing to do with her appliances she continued to press the issue. After another day or so of complaining, we just told the surveyor to move the marker to a different location. Problem solved.