I had a bench in the top a bridge rail that I wanted to include in my OPUS Projects job. Made this jig with spare wood and $16 worth of hardware from Homecheapo...
Appears to work pretty good....
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other stuff from the last few days-
Quite an innovative setup.
What keeps the triangular block holding the range pole from sliding down? Is this a one-off setup, or is it adjustable to fit different wall thicknesses?
Nice!
The hole in the triangle block is only slightly bigger than the 1 ft picket- so it's a friction fit. The tension from the 3 legs holds it in place.
I can adjust the width with my screw gun and using bigger clamps.
The short dowels can be changed out also to accommodate wider widths also.
I'm sure it's just me, but I would have thought that you'd want the antenna to be at a height above most passing vehicles. Was the traffic so light or non-existent that this wasn't a consideration?
ADT is about 4 vehicles/ hr.-
Going higher would have required projecting farther into the traffic lane- the width I ended up with wasn't much wider than the base of the bridge rail.
I'm thinking about a general solution for bridge railings and culvert headwalls, both of which tend to be close to traffic lanes.
Is that mark in the abutment or the bridge itself?
Is there any concern about movement as most bridges tend to have some sort of expansion joint to allow movement?
> Is that mark in the abutment or the bridge itself?
It looks to me as if it's in the top of the bridge rail over an abutment.
I like it. I would have just transferred the elevation over to a rod in the grass and let it eat.
We have a couple of points like that which we have to occupy each year. Here is what we use:
But your setup would withstand wind a lot better. Pretty neat idea.
> I like it. I would have just transferred the elevation over to a rod in the grass and let it eat.
I'll like Stls solution if vertical is all you need...anyone have a reason NOT to do this??
isn't that guiderail gonna cause some serious multipath?
I'd feel a lot better about it with another foot of antenna height and the vehicle moved. Passing vehicles would probably have such momentary effect as to be ok.
Not if you sit there long enough!
Very repeatable results year to year. This is for a lake elevation pool gage, and is tied to a pedestal at the dam, the bridge goes over the lake about 2 miles upstream from the dam. All of the other lakes (15) have pool gages at the dam so we directly level to them. The first time we did this we GPS'd a point off of the bridge and leveled over, but that was very difficult due to traffic on the bridge causing it to bounce. So we set the disk at the gage and now GPS it directly.
So the purpose is to make sure the pier hasn't settled, affecting the elevation of the zero of the gage.
Maybe Cantilever out a bit out away from traffic - probably get to a 4 ft pole. Need a way to ensure level/plumb- use a heads-up bubble or that Hard drive disc that was posted a while back. Use a ground plane if multi path from traffic is a concern....
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The mark is in BRIDGE Rail - I'll look in the as-builts later to day to check out the beam seats to review the expansion issues... I'll post that later.
Alternate idea
Start with a 5 gallon bucket. Cut it down to about a foot high. Shorter than the distance from point to level bubble on the short rod. Cut a 3-4 " diameter hole in the bottom center of the bucket.
Get about 10 or 12 ziploc gallon size freezer bags. Fill bags with sand or pea gravel.
Place bucket over monument. Position short rod on point. Put bags of sand in bucket to give the thing weight and hold the rod plumb.
> > I like it. I would have just transferred the elevation over to a rod in the grass and let it eat.
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> I'll like Stls solution if vertical is all you need...anyone have a reason NOT to do this??
OPUS-DB on an existing mark for one-
This is low hanging fruit- we were there yesterday for gun work in the timber. Collecting info on additional Benchmarks in the area at no added expense is a multiplier in the big picture.
> isn't that guiderail gonna cause some serious multipath?
This setup would not appear to be consistent with best practices.
Good results (or at least consistent results) could be obtained outside of best practices, but the exception does not make the rule.
But if the mask is set appropriately, I believe that a modern receiver should be able to operate effectively under those conditions.
