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I recently drove by what seemed like an unusually tall structure and used Google Maps satellite view, its distance measurement tool, and basic trigonometry to calculate that this building (some kind of grain silo at a poultry processing plant) was 175 feet tall above the ground.

But, it does not show up on the sectional map. Other nearby structures, mostly 300-350 feet or greater, do indeed show on the map.

At what minimum height above terrain does a vertical structure need to be indicated on a sectional map?

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  • $\begingroup$ I believe it is 200', but I'm not sure what regulation it is. $\endgroup$ – Ron Beyer Nov 24 '17 at 14:16
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Refer to Aeronautical Chart Users Guide 2017. There are 351,148 obstacles in the database. Generally it is when ”a manmade obstacle is 200' above the highest terrain in the quadrant”. However, “in high density areas like city complexes, only the highest obstacle is represented on the chart”. Then they do the calculations below to show the obstacle on the chart.

enter image description here

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I'll accept JScarry's answer, but here's a clearer image of the map shown in his/her image:

enter image description here

Courtesy of Skyvector.com.

P.S. I LOVE sectional maps - lots of interesting info there.

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    $\begingroup$ For some reason the Chart Users Guide is a scan of the pages in pdf form, not a real pdf. That’s why it’s hard to copy and paste. You can view a copiable version at faa.gov/air_traffic/flight_info/aeronav/digital_products/… $\endgroup$ – JScarry Nov 24 '17 at 21:09
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    $\begingroup$ You can edit @JScarry's answer to include the clearer version of the sectional chart - I don't think it warrants for a separate answer... : ) $\endgroup$ – user18035 Nov 25 '17 at 3:17

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