Hey guys,
I recently started using the Topcon Hiper ga survey gear and I have a quick question. When initially setting up my instruments, I use slant height when measuring from my control point to the arrow on the base. I use a set height of 2m for my rover and select vertical instead of slant (which I was told to do by the local distributor.)If I was to measure from the tip of my pole to the arrow on the rover and select slant rather than vertical, would this be the same thing? If this is the same and I get different elevations, would this mean there is some sort of error in the software?
(Top Surv 8).
I've never used the Topcon setup you are, but the Trimble I have used have similar height entry functions.
If you are using a fixed height 2 meter rod under your receiver then the vertical measurement from the point to the base of the receiver (ARP) is 2 meters, right? No further measurement needed. That's the major point of using a fixed height rod in the first place.
If you are determining the height of the same setup by measuring on the slant from the point to some part on the side of the of the receiver that's going to measure something else. But presuming that your receiver isn't made of jello it will be possible to calculate the vertical height to the ARP based on the slant measure. Your software will make that calc for you. There will be a setting in the dc software were you indicate whether you are measuring the vertical or the slant.
Once you convert the slant measurement to vertical there is still a difference of 30.5 mm. The slant height converted to vertical should be 2.0305m if you've got it mounted on a 2m rod.
See the image taken below taken from the manual.
OK I've got it, thank you!
Work the right triangle:
2.0000 pole height+0.0305 = 2.0305 vertical leg of triangle
0.07775 horizontal leg of triangle
sqrt(sum of squares) = 2.0320 slant distance
To be sure you understand the software, you should try each option for entering the data and see that the resulting height comes out the same.
Close, vertical would be 2m, slant would be 2.0320m which converts to a vertical of 2.0305 which equals 2.000m once you subtract the 30.50mm shown in the diagram as the vertical difference in the two different vertical reference points on the antenna.
But I'm not confused now....
.
SS
But I'm confused....
Look at the diagram posted above. The slant height is measured to a point that is vertically higher on the antenna than the ARP. The 30.50mm is the vertical difference between the ARP and the slant height measuring point.
Edit: Most GPS unit I've worked with are setup this way so that if you're using a variable height tripod you can measure to the slant reference point then convert to true vertical. Most DC and office software are programmed with the offsets for each antenna and can convert slant to vertical at the ARP. Like most things though it's good practice to make sure the software isn't lying to you.