A Little Mystery

[mrh - terre haute]

I was doing some geocaching this weekend in the vicinity of Roseville Covered Bridge - Coxville, Indiana. While doing research for my trip I noticed the BM516 at the West end of the bridge. I pull up a map of all Parke County marks with PIDs and this one doesn't appear. I stop by to check it out and this is what I found:

 

 

I think WOW! I may have found my first chiselled square. No telling how long it has been here since there is no PID to look up at NGS. I decide to walk to East end of the bridge to at the guaging station when I turn the corner onto the bridge and see:

 

within just a few feet of the other mark.

 

So my question, is the first photo a chiselled square of the type a survey crew would have left or is BM516 more likely to be the Indiana Flood Control disk in the second photo?

Edited May 9, 2005 by mrh - terre haute

[mrh - terre haute]

A quick look at Indiana Division of Water - Indiana Benchmarks on page 4 of the Parke County list reveals:

"IDNR TBM 4

In Parke County, at Coxville, on the East end of the South Abutment of the covered bridge,10 feet from the South end and on the inside of the wooden shelter of the bridge, a standard IFC&WRC bronze benchmark tablet, stamped "PAR 4". 516.277 feet NGVD 1929 2nd Order

 

and

 

IDNR TBM 9

A chiseled square in the same location as BM PAR 4

517.679 feet NGVD 1929 2nd Order

 

Looks like BM516 is most likely IDNR TBM 4. It also looks like I have one more file I have to carry around with me when I hunt these things.

 

I'd have to do some checking but these would probably be my oldest finds to date.

Attaching 2 non-official smileys:

[+BuckBrooke]

mrh,

I don't think they were placed in 1929. All of the marks in that list reference NGVD 1929, which is mentioned on the first page of that report as the elevation level of 1929 by which all marks are based. I think it is like GEOID99 or NAD 83, the reference system.

 

It's unclear to me how old those marks are; the reports don't clearly say.

Edited May 18, 2005 by BuckBrooke

[mloser]

NGVD 29 is a datum, similar to NAD 27, NAD 83, and others. For a quick overview go to NGS Datum FAQ

 

Matt

[mrh - terre haute]

Well, it looks like these marks may be considerably more recent than 1929 given that the NGVD 1929 wasn't named such until 1973. Who knows when or if the IFC&WRC adopted a more recent datum. I'm keeping my smileys though

 

Thanks - mrh

[evenfall]

National Geodetic Vertical Datum of 1929 Yup.

 

Currently superseded by the North American Vertical Datum of 1988.

 

Vertical elevations only. These are for the Bench Marks.

 

NAD27 which is superseded by NAD83 are for horizontal control

 

Rob

[mrh - terre haute]

So now the question becomes one of when did NAVD 88 supersede NGVD 1929? That would establish when the latest date the marks were set a@@-u-ming that IFC&WRC adopted NAVD 88 at its earliest opportunity.

Edited May 20, 2005 by mrh - terre haute

[mloser]

Not necessarily. You would have to know when Indiana started USING a newer datum. Some states and localities stick with what they are familiar with because their existing data sets reference it.

[+BuckBrooke]

The Albuquerque GIS office is still on the old system. From their website:

Most of the vertical control is in NGVD29 and NAVD88 (U.S. survey feet). Horizontal control is in NAD27 (U.S. survey feet). Conversion to NAVD88 and NAD83 datums is underway.

Edited May 20, 2005 by BuckBrooke

[evenfall]

Hey Guys,

 

The NAVD88 Adjustment was completed in June 1991 and made available to the Public September of 1991.

 

http://www.ngs.noaa.gov/PUBS_LIB/NAVD88/navd88report.htm

 

NGS then superseded NGVD29 and no longer does any further updates to it as a Datum. NAVD88 is now their Standard.

 

It is quite true that many municipalities have not adopted NAVD88 as their standard as yet, but the driving force is not because they like one better than the other. That would be silly as one is many times more accurate than the other. The Main reason lies in the Costs of conversion from one Datum to the other. It would mean going through a lot of data and converting it. That can be a huge amount of time and money to a small government who does not have it in the budget. They realize the drawbacks but what can they do? Budgets are Budgets.

 

It is always good to look into what Datum a Municipality is using for their Survey Markers. It can be one or the other and even in some cases a mix of both.

 

Rob

Edited May 20, 2005 by evenfall

[+We Gotta Hunt]

I ran across this yesterday.

 

 

 

IDNR BM PAR 4In Parke County, at Coxville, on the east end of the south abutment of the covered bridge, 10 feet from the south end and on the inside of the wooden shelter of the bridge, a standard IFC&WRC bronze bench mark tablet, stamped —PAR 4“. 516.277 feet NGVD 1929 2ndOrderIDNR TBM 9A chiseled square in same location as BM PAR 4.517.679 feet NGVD 1929

 

IDNR TBM 9A chiseled square in same location as BM PAR 4.517.679 feet NGVD 1929

 

I got this info from here on page 4:

park county benchmarks

 

I was looking to log this one and there is still no record for it here at geocaching.com

Is there a way to get credit for the find? My second benchmark find

[+shorbird]

If you want credit for finding a benchmark which is not listed at geocaching.com, go to Waymarking.com and log it there. There is a section for U.S. Benchmarks where you would log your find. You provide the description and coordinates.

[+We Gotta Hunt]

If you want credit for finding a benchmark which is not listed at geocaching.com, go to Waymarking.com and log it there. There is a section for U.S. Benchmarks where you would log your find. You provide the description and coordinates.

 

Thankyou shorebird