In the recent thread on "Cutting a line through the Woods", Williwaw said:
"Another method to consider is setting target(s) in a tree or utility pole up as high as you can reach. I usually use a tack or mag nail with a wad of flagging. Sort of a vertical control point. Can't set up on it but you can use it for a back sight or resection in combination with another."
I recently tried this using a total station only, (on a utility pole that I can see from several of my control points), but realized that, while it may ultimately be used as a back sight, you MUST set it in the first place as if it were a real point (using a prism and observing it's distance and azimuth). I thought of setting it as an additional back sight in SurvCE, so I had the record of it as a back sight, but it's not a point unless there's both azimuth and distance.
I remember coming across this dilemma (of NOT being able to observe angle only with "Store Points" in SurvCE) when I was doing Polaris. Not a big chance of setting a prism up there.
So, the questions for this Friday are:
1. Is it true that, (using SurvCE at least) if you want to create multiple back sight points for resection or for azimuth orientation from a known network point, you must create the points as real points. If so...
2. if you do this, would you then add them to the Starnet file and adjust them with all the rest?
3. In the case of something too distant, such as radio tower, church steeple, (or even Polaris), how is this data typically brought into a survey using SurvCE? Adding them as additional back sight records as noted above, with no distance, then put dummy HD info in the .rw5? Some other way?
I would put a distance to it...doesn't need to be right as long as the angle to it is good. ie. a far off radio tower I would just put a distance to 10,000' to it. Then when you go to your map it would be the point way off from your job site.
Back when I did a lot of construction layout I'd use "naturals" like radio towers on top of the mountains. Once I was set up on my control system then from a control point I'd record the angle to the natural. Then when I returned on another day or moved back to the CP you could just setup and backsight the natural and be up and going. I never new what the distance was. I've done the same with some artificial things like paste up targets or whatever, never knew the distance. I have a reflectorless gun now so the distance could be known to things "close in." If you have a good control network in place you can set up with only the angle to any other point but a better check is both distance and angle.
I've never used the software you are asking about. I'd think it a deficiency that you couldn't just record the angle to some object. It's probably in there somewhere.
LRDay, post: 344246, member: 571 wrote: Back when I did a lot of construction layout I'd use "naturals" like radio towers on top of the mountains. Once I was set up on my control system then from a control point I'd record the angle to the natural. Then when I returned on another day or moved back to the CP you could just setup and backsight the natural and be up and going. I never new what the distance was. I've done the same with some artificial things like paste up targets or whatever, never knew the distance. I have a reflectorless gun now so the distance could be known to things "close in." If you have a good control network in place you can set up with only the angle to any other point but a better check is both distance and angle.
I've never used the software you are asking about. I'd think it a deficiency that you couldn't just record the angle to some object. It's probably in there somewhere.
I used to do that as well. Usually a building corner next door. Then swing down down to randomly placed Prism and collect a shot which would then store a point number and angle.
When you say "swing down"....you mean just drop the telescope vertically and have your rod man place the prism in line with the back sight until you get a distance?
You couldn't really use it for a resection or adjustment without having good 3D coordinates on it. I typically shoot these things in using a peanut prism. If I had a station that I was going to occupy regularly I might sight a natural like a church steeple or radio tower, ect. and comp a bogus point using my measure angle (doubled) and a bogus distance, but being careful to note that it is only to be used for future back sighting purposes for convenience sake to save time, from that station only. Just all depends on what you want you plan on doing with it. To compute the point using a bogus distance you'd need to book the angles and use a cogo function to manually compute the coordinates for the target. Now, if you can observe the same target from multiple setups but you can't measure a distance to it directly, that'd be another thing altogether.
Good question.
With respect to StarNet and question #2, if you had multiple ties to your natural BS, you might be able to enter each tie as a 'B' record if you had a point stored for the BS. I'll check the manual, but there has to be a code for azimuth only.
There are others much more knowledgeable on this subject. Hopefully they'll chime in.
A problem with distant towers is that next year the red light or antenna you sighted may have been replaced with a strobe or differenerent mast and it isn't' always obvious.
Good thought. In my case, from my current location, there are no church steeples, radio towers or anything else that distant (except polaris of course).
