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Ok, I'm looking at an MEF of 8,700 in a quadrant. There is an elevation on one Mtn of 8360, which makes sense if you then add the vertical error of 100 , then the 200 ft man made or natural obstacle error allowance to get 8660 then round up. Got that, no problem, where I'm unsure however is that at a lower elevation there is a Mtn. marked 8082, then next to it is a lookout tower, ( tiny triangle inside a circle symbol ), the legend says that the base elevation of lookout towers are 618, if you add that to 8082 you get exactly the MEF of 8,700. So what exactly is meant by its base elevation? Since the towers is on a mtn, the spot it sits on the ground is not 618 msl , if the tower is 618 agl, then there is no calculation error added in as per the required way the chart is done, so what am I not really grasping here?

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Ok, I'm looking at an MEF of 8,700 in a quadrant. There is an elevation on one Mtn of 8360, which makes sense if you then add the vertical error of 100 , then the 200 ft man made or natural obstacle error allowance to get 8660 then round up. Got that, no problem, where I'm unsure however is that at a lower elevation there is a Mtn. marked 8082, then next to it is a lookout tower, ( tiny triangle inside a circle symbol ), the legend says that the base elevation of lookout towers are 618, if you add that to 8082 you get exactly the MEF of 8,700. So what exactly is meant by its base elevation? Since the towers is on a mtn, the spot it sits on the ground is not 618 msl , if the tower is 618 agl, then there is no calculation error added in as per the required way the chart is done, so what am I not really grasping here?

 

 

Hey there,

I think the 618 in the legend is just an example. The base elevation (the MSL altitude that the tower is sitting on) for your example is 8082, and the top of the tower is some unspecified altitude above that. I think...maybe I'm misunderstanding your question. If it's really a lookout tower (like a forest service fire cabin), it's probably less than 50 feet tall.

--c

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Hey there,

I think the 618 in the legend is just an example. The base elevation (the MSL altitude that the tower is sitting on) for your example is 8082, and the top of the tower is some unspecified altitude above that. I think...maybe I'm misunderstanding your question. If it's really a lookout tower (like a forest service fire cabin), it's probably less than 50 feet tall.

--c

 

Not only is it in the legend of the chart, it is also defined as such in the 7th edition Aeronautical chart user's guide.

They both say the symbol is a lookout tower. So I'm now leaning toward the possibility that there is a standard height to which lookout tower is made. Then one is supposed to look at the elevation number next to the tower symbol and if you want to know the mtn. height you can subtract the 618. That in my estimation has to be it because it says Elevation Base of tower. BTW I'm looking at the quadrant right above Boise A.P., just to the left of the river going up from Smiths Ferry to Cascade. I'm doing my Commercial X-country up to Cascade this Friday. Then my night one on Monday to Mnt. Home, trying to knock out all the night stuff ASAP before sunset moves much further beyond 9pm. Luckily offical hrs I can start logging night time is 9:07 pm, so I'll make it halfway to Mnt. Home with leftover sunlight still about till 9:45, although personally I like flying at night.

Aren't you just about to be completely done???

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The legend is just an example. The elevation shown at the lookout tower is the terrain elevation at the base of the tower. and 618 is an example. There are no fire towers that are 618 feet tall, not even close. They aren't even tall enough to have their own height shown, as are communications towers, where the height is shown in parentheses, with the elevation of the top shown in bold.

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I wish...I schedule a checkride, it gets canceled. Just got back in town this week for my 4th shot at sitting for it. You working on your instrument XC?

--c

 

No, commercial. Got my day on Friday, my night on Monday, then gonna try and bust out the night solo stuff soon after. Prolly take the written week after next.

Then keep reading and studying for the checkride till that time comes, will also work on my CFI stuff while doing CPL stuff so I can get it all done around the same time.

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