Extrusion Bridges

I have been looking at the BGL format on Extrusion Bridges in the wiki

When looking at the polylines points, the altitude values for the mid points show very high values > 3000.

After reading Arno's post on how to calculate the offset displacement, it does not make any sense these values that are so high (visually the bridge is 60 feet tall).

I am working with P3D and I am at Sea Level in this case.

Any hints or insights on this ?

Thanks !
 
Last edited:
I found the answer maybe here

Do I need to divide that value by 1000? Also to calculate the average height you need to exclude the end negative values?

Thanks
 

arno

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Yes, that document indicates the altitude is stored in 1/1000 meters as integer. So you need to divide by 1000.

Why you want to exclude the end points?
 
Well, maybe I misunderstood your article.
So you need to keep them to calculate the offset, correct?
 

arno

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The article is about creating bridges, when you read them from existing file you can just keep the values as they are.
 

arno

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For each bridge two positions are specified for which the altitude is sampled. The altitude specified is relative to the line between these points.
 
Thanks. So how do you calculate the height of the bridge ? Or the height of each part ? Thanks
 

arno

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I'm not sure I understand your question. What are you trying to achieve?
 

arno

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Hi,

It's hard to tell the agl height at any point of the bridge, as it depends on the terrain elevation.

But if you ignore the terrain elevation you could just use the elevation of the different points and subtract the average elevation to compensate for the weird offset that FS introduces.
 
But if you ignore the terrain elevation you could just use the elevation of the different points and subtract the average elevation to compensate for the weird offset that FS introduces.
Thanks Arno. So, just to understand: this is done with the BGL data as described in the wiki? Correct?
 

arno

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Yes, but if you have a bridge over a canyon or so the height agl for some parts will be different of course. Not sure if that's relevant for your application.
 
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