Ground elevation on a sectional chart

[ruggb]

OK, this is what I found in the Aeronautical Chart User’s Guide;

"Manmade features used by FAA Air Traffi c Control as checkpoints use a graphic symbol shown in black with the required elevation data in blue. The elevation of the top of the obstacle above Mean Sea Level (MSL) and the height of the structure (AGL) is also indicated (when known or can be reliably determined by a Specialist)."

The 2676 number IS the elevation reported of the obstruction in MSL. There is no height (xxx) given because it has not been verified. (It may be under construction or maybe not). I think a better term for UC would be UnConfirmed. It could be UC because it is unfinished or under construction or it could be they have not gotten to it yet.

SO, I am now in agreement, the answer is 2000-2500 and that is based on the fact that there is no 2500' contour. It is over 2000', but under 2500'. Obviously, (yeah now I think of it) the 2676' can't be ground level as there is no 2500' contour.

 

[kadras]

I don't think so. They are not going to have contours for 2676 ft. Windmills will typically be on high ground. An MSL of 2676, or 176 ft above the last contour is perfectly reasonable. There would not be another ground contour.

What is MSL? Are you saying that is an estimate of what the Windmill elevation WILL be?
I'm having my doubts about that. IMHO, Mean Sea Level refers to a ground level, not a structure height. When anything else is marked it is marked MSL + its height.
Do you have any reference for that view?

I will present it to my neighbor pilot tomorrow.

1. Tropic correctly explained why 2000 to 2500 is the correct answer: "The questions reads ground elevation in the tan area, not highest man made object. Correct UC means under construction. Since the legend clearly states 2000 - 3000 and a contour every 500 feet with no contours shown on the map it has to be 2000 - 2500" There is no need to be checking the heights of obstructions to calculate the ground elevation.

2. The UC means under construction or "reported: position and elevation unverified." The 2676 is indeed an estimated max height above mean sea level (MSL). All of the obstruction heights are MSL, under construction or not. An aircraft flies at MSL altitudes, not AGL, so needs to know where the top of the obstruction is, regardless of how tall it is. The height above ground level (AGL) is the number in parentheses under the MSL height, and is subtracted from the MSL number. Note the UC tower south of the wind turbine farm as 2508 UC and the tower south of it as 2524 (303). The tower height is 303 and the top is at 2524. Distractingly, north of the turbine farm there is a non-turbine tower at 2676 MSL, same as the turbine farm, with a tower height of 495. Here is the notation from an FAA sectional.