# Transit

Posted by Henry in MI on April 15th, 2001 11:26 PM
In reply to Transit level by Greg on April 15th, 2001 10:17 PM [Go to top of thread]

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Greg, I'm not real experienced. Steve or someone else may be. The process though is to start from a base or known elevation, then use the transit to see if you are going up or down from there and how much. Set the transit on top of the known elevation or the spot you want to start from. Level the transit and measure how high the telescope tube is from the known spot. Have your rodman stand where you want to know the next elevation and put the rod down on that spot. You look through the telescope and see how high that is by reading the ruler on the rod. Do the math from your known telescope height and you will know how much higher or lower the new spot is from the base elevation. Having the known (telescope tube height) and the unknown (elevation you see when you look through the tube) spot at the same height above the ground means that they are level. Looking through the tube and seeing a measurement that is less than the tube height means that the new spot is higher and the difference is how much. Seeing a larger measurement says the new spot is lower and the difference is by how much.

It is pretty easy to figure how much higher or lower the four corners of a patio or parking lot are, for instance, but it does take some time, you have to be precise, and you will want to keep good notes of your elevations actual and calculated. It is pretty easy to think the new one is higher when it actually is lower if you confuse the numbers. Having the transit exactly level, according to the bubble, is critical.

Hope you didn't have too much trouble getting through this but it is difficult to explain. You might look around the web for a site with drawings or pictures of how this works.

Henry in MI