Shooting Sequences

As far as I know, it's largely personal preference. The BS > FS ^ BS > FS sequence is the traditional sequence that was commonly used with optical (non-electronic) instruments in order to accumulate angles on the plate.

The BS > FS ^ FS > BS takes a little less time to execute (maybe, I've never actually timed it) so that's my preference.

BS > BS ^ FS > FS sequence would be best if you only had one target.

There may also be issues with some data resolution software.

When I run the robot I use Fs Fs Bs Bs since it's already in the Fs position.

Aloha,
Thank you Mark, Djames for confirming that these are largely personal preferences. Much appreciated. Mahalo!

I prefer BS > FS ^ FS > BS, as it allows less occupation time at the foresight. This comes in handy when in traffic, windy areas, animal cages, etc.;-)

Back in the day when we recorded angles in a field book, I always preferred BS BS FS FS. That way I could tell real quick if I made a pointing error. The Lietz SDM 3E I used had an index error of 10" so if the back site was vert far off of 179-59-50 I usually had a bad pointing. We always closed the horizon to get our second set. When I stared using TDS 48, and a Lietz Set II, I used the same sequence, but after I finished the first set, I would set 0 on the foresite point and do another set. It seemed to work well. Our new total stations aren't as easy to set zero on.

> I prefer BS > FS ^ FS > BS, as it allows less occupation time at the foresight. This comes in handy when in traffic, windy areas, animal cages, etc.;-)

Aloha, Jack:
Very interesting point. This gives me an idea to work around fast when I am in the pasture with our over friendly dairy cows. Thanks

Shooting Sequencesribrach Calibration

Thanks Steve! Aloha

BS > FS ^ FS > BS

This is the one I use with robotics. But again, it's just a preference.

IMO, though, some of the other sequences really only measure one horizontal angle.

For example: BS > BS ^ FS > FS

Yes the gun turns horizontally three times, but there is only one measurement on the interior angle observed. With BS > FS ^ FS > BS you get two horizontal angle measurements, and on opposite sides of the plate, which is supposed to help mitigate any collimation errors.

> With BS > FS ^ FS > BS you get two horizontal angle measurements, and on opposite sides of the plate....
You really don't with modern instruments. You get points on the plate recorded, from which angles are computed. Since the plate is fixed throughout the process you do not accumulate angles like you would on an optical instrument.

BB FS^FS BS

Started using this format pre-data collector days and running traverses for mapping projects for NGS project. Then adopted the format for all work. Less tromping around instrument and ease of calculating angles with a pencil in the field book page/columns.

We would do 4 sets and then take a mean. Here are twqo sets

BS 0° 00' 00"
100° 30' 45"
FS 100° 30' 45"
100° 30' 46.5"
FS 280° 30' 52"
100° 30' 48"
BS 180° 00' 04"

BS 0° 00' 00" 100° 30' 48.0"
100° 30' 48"
FS 100° 30' 48"
100° 30' 49.5"
FS 280° 30' 54"
100° 30' 51"
BS 180° 00' 03"

Later when we went to DC's (TDS Pro), I kept this format. Why Change?
When I stated using Microsurvey Field Genius, the software lets you observe in any sequence by point number or point numbers. So if the FS was being set, one could observe the BS shots to expedite the process.

> BB FS^FS BS
>
> Started using this format pre-data collector days and running traverses for mapping projects for NGS project. Then adopted the format for all work. Less tromping around instrument

The other advantage is that by finishing on your backsight you practically eliminate any blunders from a bumped gun or slipped lower motion (remember those?). With BS-BS-FS-FS, you can bump the setup after the second BS reading and still get acceptable FS readings; you'd never know that the calculated angle is bad. BS-FS-FS-BS is kind of like closing a level loop back on the starting bench mark.

Aloha, Robert:
Thanks for the example and explanations!

> > BB FS^FS BS
> >
> > Started using this format pre-data collector days and running traverses for mapping projects for NGS project. Then adopted the format for all work. Less tromping around instrument
>
> The other advantage is that by finishing on your backsight you practically eliminate any blunders from a bumped gun or slipped lower motion (remember those?). With BS-BS-FS-FS, you can bump the setup after the second BS reading and still get acceptable FS readings; you'd never know that the calculated angle is bad. BS-FS-FS-BS is kind of like closing a level loop back on the starting bench mark.

Aloha, Jim:
This is a very good observation. This is another good point! Survey Pro field software actually uses this as default setting.
Thanks!

Aloha,

I put spacing into my post to show how they were depicted in the FB columns but when I hit "post' the format was changed to eliminate the spacing. So to me, it looks very confusing to what I intended to post.

Sometimes,I do not look at my posts after I hit send.

R

BS 0° 00' 00"
......................100° 30' 45"
FS 100° 30' 45"
..................................100° 30' 46.5"
FS 280° 30' 52"
......................100° 30' 48"
BS 180° 00' 04"
......................................................100° 30' 48"
BS 0° 00' 00"
......................100° 30' 48"
FS 100° 30' 48"
..................................100° 30' 49.5"
FS 280° 30' 54"
......................100° 30' 51"
BS 180° 00' 03

Company I once worked for used:

Observations Scope Direct
BS~0.1
FS1
FS2
FS3
FSn
BS~0.2

Observations Scope Reversed
BS~180.1
FS1
FS2
FS3
FSn
BS~180.2

Note: beginning backsight angles could vary- corresponding reversed about 180 deg more. Normally, this system was used for directional instruments, not the movable lower plate or repeating instruments.
_______________
Example

Observations Scope Direct
BS 00° 00' 05"
FS1 100° 30' 45"
FS2 146° 22' 52"
FS3 217° 07' 16"
FS4 254° 53' 05"
BS 00° 00' 11"

Backsight Average 00° 00' 08"
Reduced Angles Direct
FS1 100° 30' 37"
FS2 146° 22' 44"
FS3 217° 07' 08"
FS4 254° 52' 57"
___________

Observations Scope Reversed
BS 180° 00' 12"
FS1 280° 30' 50"
FS2 326° 22' 57"
FS3 37° 07' 15"
FS4 74° 52' 55"
BS 180° 00' 08

Backsight Average 180° 00' 10"
Reduced Angles Reversed
FS1 100° 30' 40"
FS2 146° 22' 47"
FS3 217° 07' 05"
FS4 254° 52' 45"

==================
.Angles Averaged
==================
.FS1 100° 30' 38"
.FS2 146° 22' 46"
.FS3 200° 07' 06"
.FS4 210° 52' 51"
________________________

Anyone else ever use this system?

I was taught by a PC to do the following:

BS > FS > BS ^ BS > FS > BS.

We would zero the TS on the BS and turn and record an angle direct, e.g., 53-07-44 and return to the BS and record the observation, say 359-59-52. Do the same reversed but not zero the gun. Afterwards, we would take one-half the difference of the observed angle and add or subtract it to the observation; in the example above, we would add four seconds to the observed angle thus producing 53-07-48. This does result in considerably more backsight distance observations versus foresight ones.

I've done it this way until very recently, now I do BS > FS ^ FS > BS.

For the record, with primary control and monument referencing I still book my observations.

Aloha, Alan:
That's a lot of observations. I wonder if this is necessary with the modern guns? i.e. with 2" or 3" precision...

Only 1 reading on each face for the foresights.
The way to get (close to) the stated manufacturers accuracy is to take multiple readings one each face.

> For the record, with primary control and monument referencing I still book my observations.

Aloha, Sellman:
By "book" you mean manually writing it down right? If yes, may I ask why? Not questioning, just wanted to understand. Thanks