Are HH2 coordinates on azimuth marks useful

[+LSUFan]

Hi Everybody. We went and found triangulation station SANDY CQ2730, yesterday. We easily found the station and it's two nearby reference marks. Since the station mark already has adjusted coordinates, I know I can't improve on anything there.

 

We then went and found the azimuth mark for SANDY up the road. My question for the experts here is:

 

Would it be useful to anyone to put the HH2 coordinates into a NGS recovery report for SANDY, for the azimuth mark?

 

I kind of have a quasi understanding on exactly what the azimuth marks purpose is.

 

Thanks

Edited September 18, 2009 by LSUFan

[Papa-Bear-NYC]

Hi Everybody. We went and found triangulation station SANDY CQ2730, yesterday. We easily found the station and it's two nearby reference marks. Since the station mark already has adjusted coordinates, I know I can't improve on anything there.

 

We then went and found the azimuth mark for SANDY up the road. My question for the experts here is:

 

Would it be useful to anyone to put the HH2 coordinates into a NGS recovery report for SANDY, for the azimuth mark?

 

I kind of have a quasi understanding on exactly what the azimuth marks purpose is.

 

Thanks

It would certainly be useful to benchmark hunters (us, in other words) since they are usually hard to find because the bearing from the station is typically given in the box score, but not the distance.

 

It would probably be of no use to surveyors or the NGS since with high accuracy GPS, they don't need it like they once did. (in fact they probably don't need the triangulation station either, but that's another issue).

 

What they were used for was to give a surveyor the ability to determine the true direction to the other stations they were observing, rather than the relative direction, since the only thing they measure is the angles between the station observations. They would observe the azimuth mark, and then station 1, 2, and 3 (whatever) and then later in the office, they would look up the exact bearing to the azimuth mark (from the datasheet, or file cabinet in the older days), and then use that to calculate the exact bearing to the other observed marks.

 

So by all means, put them into your log here at GC, but I wouldn't bother reporting them to the NGS.

Edited September 18, 2009 by Papa-Bear-NYC

[Bill93]

I would say if you are reporting to NGS, include the coordinates for the AZ mark. It may of minimal value, but what does it cost? Just a minute of your time and a couple dozen characters in a data file.

 

I once tended to include coordinates for other Reference Marks, before I realized that those could be computed with great accuracy from the box score information. Now I would not include those.

[+Black Dog Trackers]

I'd put it in your NGS recovery report.

It's possible that they will upgrade CY4680 with your HH2 coordinates. It appears to have scaled coordinates now. You might try sending them to MRAS as per this thread.

[MarkSetter]

HH2 coordinates would be useful for future recoveries of the monument and I believe that NGS would encourage that they be listed in the description of the recovery that you submit. As Pappa Bear NYC mentioned, azimuth marks are very useful to surveyors for determining directions in their surveys. The geodetic azimuth is listed on the data sheet. I copied the following from CQ2730's datasheet:

 

CQ2730|---------------------------------------------------------------------------------------------

CQ2730| PID Reference Object Distance Geod. dddmmss.s

CQ2730| CQ2722 MONROE RAD STA KLIC MAST APPROX. 3.0 KM 0293608.0

CQ2730| CQ2729 SANDY LADH A PT 1971 7.873 METERS 03901

CQ2730| CY5473 SANDY RM 1 12.267 METERS 17454

CQ2730| CY5474 SANDY RM 2 12.229 METERS 35536

CQ2730| CY4680 SANDY AZ MK 3584639.3

CQ2730|---------------------------------------------------------------------------------------------

 

So the geodetic azimuth from "SANDY" to "SANDY AZ MK" as listed above would be 358 degrees, 46 minutes, 39.3 seconds. However, most surveyors would be more interested in the grid azimuth, which can be determined by applying the Laplace correction and the convergence angle to the geodetic azimuth as found on the data sheet.

[AZcachemeister]

I tend to get my data from the NGS datasheets, rather than GC.com.

So, I would definitely appreciate the inclusion of the (HH2) co-ordinates for ANY mark you might locate (adjusted stations not withstanding). As Bill93 says, what harm can it do to include them?

[DaveD]

Just a minor technical correction to MarkSetter's post. The LaPlace correction is applied to an astronomic (e.g. Solar or Polaris) azimuth to determine the geodetic azimuth. The geodetic azimuths published by NGS on the datasheets already have this taken into account. To compute a grid azimuth from a geodetic value you only need to apply of the reverse sign of convergence angle.

[MarkSetter]

Just a minor technical correction to MarkSetter's post. The LaPlace correction is applied to an astronomic (e.g. Solar or Polaris) azimuth to determine the geodetic azimuth. The geodetic azimuths published by NGS on the datasheets already have this taken into account. To compute a grid azimuth from a geodetic value you only need to apply of the reverse sign of convergence angle.

 

Yes, Dave is right. I know better than that. That's what I get for posting at 10:18 at night.

 

I stand corrected. My apologies for the mistake.

Edited September 20, 2009 by MarkSetter

[+jwahl]

I thought I would add a strong vote for reporting postions on Azimuth marks. The stations themselves may seem like they are somewhat obsolete, but having used many of them in my own ancient surveying career, I still like the idea. Finding an azimuth mark was often hard because no distance was usually given to them. There are probably still some occasions where any info would help preserve them even though perhaps they are not used as much as in the past. To me getting a position on one is really a value added thing, just like for scaled marks. They are technically part of the station.

 

The whole issue of to what degree monumented marks are useful to surveyors can be pretty esoteric. Yes, today with GPS, a surveyor may not even use nearby marks for horizontal control at all. But not everyone has GPS and it is sometimes still nice to have a check.

 

Vertical control is a whole other thing.

 

Hopefully if you find an AZ mark you get a position and it can go into the report. Heck someday all those GPS birds might fall out of the sky and terrestrial surveying may come back into vogue. Who knows!

 

jlw

[MarkSetter]

I thought I would add a strong vote for reporting postions on Azimuth marks. The stations themselves may seem like they are somewhat obsolete, but having used many of them in my own ancient surveying career, I still like the idea. Finding an azimuth mark was often hard because no distance was usually given to them. There are probably still some occasions where any info would help preserve them even though perhaps they are not used as much as in the past. To me getting a position on one is really a value added thing, just like for scaled marks. They are technically part of the station.

 

The whole issue of to what degree monumented marks are useful to surveyors can be pretty esoteric. Yes, today with GPS, a surveyor may not even use nearby marks for horizontal control at all. But not everyone has GPS and it is sometimes still nice to have a check.

 

Vertical control is a whole other thing.

 

Hopefully if you find an AZ mark you get a position and it can go into the report. Heck someday all those GPS birds might fall out of the sky and terrestrial surveying may come back into vogue. Who knows!

 

jlw

 

As a surveyor and a strong proponent of GPS, if there were a horizotal control mark and an azimuth mark very close to a project that I was working on, I would seriously consider using these marks instead of setting new points with GPS equipment. Of course, this would depend on the project needs. Even with the use of GPS these marks can still provide checks, which are necessary in our work. Therefore, I am all for any bit of information that will help to recover these marks in the future.

 

Excellent post jwahl.

[+LSUFan]

Many thanks to everyone for their replies. I always appreciate your advice and time spent, educating others like myself. I always learn so much from these forums, and really enjoy reading them.

[+shorbird]

LSUFan,

 

I will add my name to the list of those who would definitely include the coordinates for the azimuth mark in the NGS report. Any piece of information which could be useful, such as the coordinates, should be included in the report. BTW, your closeup shots of the CQ2730 disks were excellent. Keep up the good work!