What are those things called for seeing a BM location from the air?

[+Black Dog Trackers]

I'm referring to those painted 3-blade things or the similar white plastic bands spiked to the ground that are near benchmarks for viewing the location from the air.

 

What are they called?

 

[This message was edited by Black Dog Trackers on July 06, 2003 at 11:56 PM.]

[Z15]

Aerial targets, control panels etc.

 

fyi

Surveyors use them for any control point they might want. We rarely put them on NGS bench marks at the DOT. We were given a map by the photogrametry section with locations they want us to set control and paint or panel targets. It was along the flight path of the photo plane. We (MDOT) did what they called "photo triangulation" where we would set groups of 5 panels in an area, survey horizontal and vertical control with GPS. The size of the aerial target was normally with 8 ft legs for mapping flights, larger targets than 8 ft usually meant high altitude flights for route location studies.

[+happycycler]

I have noticed reference to *Picture Points* in a couple of BM datasheets -- identifying the point where the target was placed, I think. (I believe that they gave the distance and direction from the picture point to the main mark.)

[Couch_Potato]

quote:

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What are they called?

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Eyesores

 

I'm not lost!

I just don't know where I am.

[+GEO*Trailblazer 1]

31-34. Map Control.Maps prepared by methods of photogrammetric surveying are based upon 2 types of control: field or ground control,which may be obtained in a variety of ways,and secondary or photocontrol,which is generally obtained by phototriangulation or aerotriangulation but sometimes is obtained in the field. Ground control is classified in 4 ORDERS of precision,as follows:First 1/25,000, Second 1/10,000. Third 1/5,000. Fourth 1/2,000 (approx.)Maximum error in horizontal location. Fourth order control is usually refered to as secondary control but is sometimes refered to as (PICTURE-POINT)control or supplemental control.A Control point obtained for photogrammetric surveys is also called a PHOTO CONTROL POINT,A PICTURE POINT,or a GROUND CONTROL point.1st Order control is established by the U.S. Coast and Geodetic Survey,and second and third order control by the U.S. Geological Survey,the Corps of Engineers,and other mapping agencies of the Federal Gov.,States,Municipalities,or other survey agencies.The Locations and elevations for 1st 2nd,and 3rd-order control are permanently monumented and published.The Published locations and elevations of the control can usuaslly be obtained by inquiry adressed to the Head of the Dept. or Bureau which established the control.........................

 

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