Benchmark stations

[+Student Camper]

What is meant by "station not occupied", this term is used frequently in the datasheets.

[Papa-Bear-NYC]

What is meant by "station not occupied", this term is used frequently in the datasheets.

It means the persons reporting on the station did not actually set up their instruments to make measurements to other stations. This is done when the station is first established (except as mentioned in another thread that intersection stations are never occupied). It may or may not be done later when the station is checked.

 

Sometimes old stations are "occupied" at a later date to make measurements to new stations nearby. Then the location originally determined for the station when it was established, can be used to ascertain the locations for the newer stations.

 

This is done all the time when surveyors use established stations to determine the locations for a new project, say a shopping center. This is what is meant by "control", a word you will also see used. You will hear a statement such as "NGS station XYZ was used for control in the survey for the shopping center".

 

These can be horizontal control (location) or vertical control (elevation).

 

So you can immediately say that when we non-professional benchmark hunters check on a station, we never "occupy" that station, although I doubt any of us would ever use that terminology. Remember also that all the recoveries done prior to maybe the 1970s or 1980s were done by professionals, often in the line of their work. So for them "occupying" a station was more frequent than not.

Edited November 22, 2010 by Papa-Bear-NYC

[Z15]

It will also mean that although the survey party used the station to sight upon from another station afar, they did NOT come to this station at take physical measurements that time. By site upon I mean someone went there and shown a light or some other means so the surveyor on a distance point could observe it.

 

Stations that are not occupied are often given a lower accuracy due to this. In surveying you can never check on a position enough times.

 

Sometimes is impossible to occupy the point, time constraints, obstructions that prevented a tower being built, no permission for entry, decision made by supervision that it was not needed and so on.

 

edited to add omitted word

Edited December 7, 2010 by Z15

[Wintertime]

It will also mean that although the survey party used the station to sight upon from another station afar, they did come to this station at take physical measurements that time.

 

Okay, I'm lost: if they did come to this station to take physical measurements, is that not occupying the station??

[Papa-Bear-NYC]

It will also mean that although the survey party used the station to sight upon from another station afar, they did come to this station at take physical measurements that time.

 

Okay, I'm lost: if they did come to this station to take physical measurements, is that not occupying the station??

The key is FROM the station and TO the station.

 

When a station is occupied, the surveyor set up his stuff on the station and observed other station. So those observations are FROM the station TO other stations.

 

If for example, a station is a flag pole, and the surveyor isn't sitting on top of the station to observe other stations (which you can't rule out - I'm sure someone did that somewhere) - than that flag pole was NOT occupied. This is not to say the surveyor didn't walk over to it to check it out.

 

Sometime mountain peaks are not occupied, just observed from other stations. I think the Devils Tower or whatever it's called was described as such in a recent thread.

 

The First (and probably second) order stations were always observed FROM (= occupied) and observed TO from other stations. That two-way measurement gives the higher accuracy.

 

But remember, the process of observing FROM a station (i.e. occupying it) means the surveyor set up his stuff (a theodolite usually) and measured angels to other stations. The process of observing TO the same station from another station, means they had to set up something on the target station (assuming it was NOT a flag pole) to see it from afar and they almost certainly moved the theodolite out of the way -- and, in fact, was most likely done on a different day. This might be a light (night observations were frequently done) or a pole erected at the station.

 

In some cases, there was a ready made object, like the cross on a church steeple which was carefully measured to be exactly over the surveyor working in the belfry, or the top of a water tank which the surveyor actually went up to and did his stuff there (hopefully without falling off and getting himself killed). In these cases (the cross and the water tank) which are of a type NOT usually occupied, were in fact occupied due to special circumstances -- or due to a very daring surveyor.

Edited December 6, 2010 by Papa-Bear-NYC

[AZcachemeister]

It will also mean that although the survey party used the station to sight upon from another station afar, they did come to this station at take physical measurements that time.

 

Okay, I'm lost: if they did come to this station to take physical measurements, is that not occupying the station??

 

I think it's a typo, and the word 'NOT' was left out...

 

they did NOT come to this station and take physical measurements that time.

[Wintertime]

I think it's a typo, and the word 'NOT' was left out...

they did NOT come to this station and take physical measurements that time.

That would be my guess, too. Z15, you there?

 

Patty

[Z15]

I am here but not all there.....

 

yes a typo, I corrected it. I had problems editing that post on that day, for some reason the site would not respond for a long time

Edited December 7, 2010 by Z15

[Wintertime]

I am here but not all there.....

 

yes a typo, I corrected it. I had problems editing that post on that day, for some reason the site would not respond for a long time

Yeah, the Groundspeak forums get flaky quite regularly.

 

Thanks for clarifying your posting.