Structure Lesson 301: What is it?

[Doug Vahrenberg]

Ok I've got a Humminbird Screen Capture that might test some of you...Let's see what you all think is happening in the image....

[mark poulson]

Old roadway, approach, and bridge support.

[Doug Vahrenberg]

This is the old highway and the Bridge Pilings hold up the new Bridge. What's unique is the Concrete Box Culvert under the road way and you can see where the material has eroded some on the left side or downstream side. There are three small ledges that appear. The two crisp white ones are where the sonar hit it directly returning a strong signal. The Dark on is where the absence of sonar is for going over the drop and creates a defined shadow. Also neat how you can see the concrete pavement, rocks/gravel on the shoulders and then the base. On left side it's built up on the top right the hill has been excavated to flatten the roadway.

[mark poulson]

I thought the mounds to the right and left of the box culverts were the old road and approaches. I thought what turns out to be the old road was just a ridge running across the area.
I totally missed the box culverts, which I thought were shadows from old bridge supports, and the new bridge pillars.
Looks like it'll be a while before I teach your class.
How does the photo relate to the sonar image?

[Doug Vahrenberg]

This is an example of a Box Culvert under a road - similar to the one running running under the old road in the SIde Imaging Screen Capture.