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Matched Rods?
I need advice on using matched barcode rods to complete a third order level run using a Topcon DL-502 level. We have 1.25 miles left of a 3.1-mile run. Do matched rods mean that they were manufactured to be matched rods? What if there’s a 0.005′ discrepancy, for example, between the rods we’re using now? How would you compensate for that? We have 3 crews and 3 rods. The rods are about 10 years old. The office wants to use a second rod to speed up the work so we can finish the run tomorrow.
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7 Replies
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Always use an even number of turns, with the “A” rod on the bench mark at the beginning mark and the ending mark. It won’t matter if the “B” rod is matched or not, just so you can get a reading.
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You’re using two rods to speed the run up? Instead of leap-frogging a rod and level, you’re moving two rods forward with the level?
Rod 1 occupies the BM, Rod 2 occupies TP1, then level moves between TP1&2 Rod 2 moves to TP2, Rod 1 moves to TP1, repeat?
Or, are you moving the back rod with the level like I believe Dave mentions.
Either way would speed up the run, however, just over a mile shouldn’t take too long.
When you measure the rods are they matching?
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It doesn’t matter if the rods match or not. Just use the same rod on the points you want an accurate elevation. Hypothetically, if one of the rods was 1.23′ off, you would have a bad elevation on the ground where you took the reading but the instrument would not be affected. Or look at it this way. It doesn’t matter if you set the rod on the flowline or the top of curb, you will get different readings but it doesn’t affect the accuracy of your loop. A bad rod only puts a bad elevation on the ground, so make sure you sight the good rod at any points you want a good elevation.
You would get bad information if you used different rods on the same point though. If you ran a loop sighting 2 rods on each turn, both the good rod and the bad rod would give the same differential between the ends of the loop.
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Yes yes. We called them red rod so one rod had a red tape or whatever on it. But the even number of turns and making sure that they land starting and ending. Correctly.
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A good crew should be able that’s on their A game is 5 miles per day average. No matter if it’s a digital level or reading three wires manually. Note keeper rod persons instrument person.
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Update
We finished the remaining 1.25 miles in 3 hours using 2 rods. The rods were exactly the same height. We used our rod for backsights and a borrowed rod for foresights. I offered to buy the crew lunch if we closed flat. I suggested our rodman would buy lunch if we closed with an unacceptable error. We closed with 0.007′. Thanks to everyone who responded.
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Is that feet or meters.
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