In 1915, the Commonwealth of Massachusetts Harbor and Land Commission published an Atlas of the Boundaries of the towns of (Berkshire County) and Middlefield (Hampshire County). The field work was performed in 1911-1914. The Atlas describes the corners of the subject towns and the lines that run between them. Included in the Atlas is the following statement
[INDENT]"The triangulation of this survey is based on that of the U.S. Coast and Geodetic Survey, whose officers have given us material assistance in the adjustment of the triangulation system. The projection is based on the "Clarke Spheroid" and the astronomical data adopted by the U.S. Coast and Geodetic Survey in 1880."[/INDENT]
I have completed a small survey of an existing bridge which lies near the town line running between two of these towns, and I am wondering whether I might estimate where the bridge is located in relation to the town line.
The Atlas provides the Geographical Positions of Town Corners in a table, with the latitude and longitude specified for each corner. The line runs as follows:
North Point:
Latitude 42 22 50.74
Longitude 73 04 08.22
South Point:
Latitude 42 20 23.17
Longitude 73 03 53.06
Short of actually observing the location of the stones at either end of this line, what procedure might be followed to convert the published latitude and longitude to State Plane Coordinates (MA Mainland)? What are the associated accuracies of such a conversion?
NGS has a tool at http://www.ngs.noaa.gov/cgi-bin/spc_getpc.prl which allows for conversion between NAD83 or NAD27 Geodetic Positions to State Plan Coordinates. The work published in the Atlas predated the establishment of NAD27, but both appear to be based on the Clarke Spheroid.
Here are the results I get using this tool:
North Point
=======================================================
Latitude Longitude Datum Zone
INPUT = N422250.74 W0730408.22 NAD27 2001
=======================================================
EAST(X) NORTH(Y) AREA CONVERGENCE SCALE
FEET FEET DD MM SS.ss
----------- ----------- ---- ----------- ------------
176105.635 507045.450 MA M -1 3 14.07 0.9999694806
South Point
=======================================================
Latitude Longitude Datum Zone
INPUT = N422023.17 W0730353.06 NAD27 2001
=======================================================
EAST(X) NORTH(Y) AREA CONVERGENCE SCALE
FEET FEET DD MM SS.ss
----------- ----------- ---- ----------- ------------
176969.231 492088.897 MA M -1 3 3.89 0.9999674921
Any comments or observations would be most appreciated.
What you have from the NGS software are NAD27 State Plane coordinates. If that's what you want, then you're home.
If you want to convert the old published coordinates to NAD83 State Plane for comparison to your recent survey coordinates, use this program first: http://www.ngs.noaa.gov/cgi-bin/nadcon.prl to convert the NAD27 lat/lon to NAD83 lat/lon. Here is the North Point converted to NAD83.
Output from NADCON for station
North American Datum Conversion
NAD 27 to NAD 83
NADCON Program Version 2.11
==============================================================================
Transformation #: 1 Region: Conus
Latitude Longitude
NAD 27 datum values: 42 22 50.74000 73 04 8.22000
NAD 83 datum values: 42 22 51.05212 73 04 6.58608
NAD 83 - NAD 27 shift values: 0.31212 -1.63392 (secs.)
9.631 -37.378 (meters)
Magnitude of total shift: 38.599(meters)
NGS HOME PAGE
Then use the State Plane conversion program you used before to convert the NAD83 lat/lon to NAD83 State Plane.
I think that the accuracy can vary quite a bit, depending on your location. The ellipsoids are different and the underlying assumptions for NAD27 and NAD83 State Planes are significantly different.
Thanks, Teach! The tool I had used and provided a link to is described as follows:
[INDENT=1]This utility uses NGS program SPCS83 or program GPPCGP
to convert NAD83 or NAD27 Geodetic Positions
to State Plane Coordinates (SPC)[/INDENT]
[INDENT=1] [/INDENT]
Am I correct to conclude that Geodetic Positions (Lat Long) and SPC (XY) must both be related to a specific datum (i.e. NAD83 or NAD27)?
I will use the process you describe and see what I come up with.
You're in the same boat I'm in.
Those are most likely United States Standard Datum not NAD27.
It's more complicated.
Scott Zelenak, post: 364451, member: 327 wrote: You're in the same boat I'm in.
Those are most likely United States Standard Datum not NAD27.
It's more complicated.
Yes, Scott, that sounds right. According to Wikipedia https://en.wikipedia.org/wiki/North_American_Datum , the USGS adopted the US Standard Datum in 1901. That would have predated the subject field work (1911 to 1914) and preceded the adoption of NAD27. I don't suppose NGS has any sort of tool that would convert from US Standard Datum to NAD83?
A spheroid (ellipsoid) is just a shape, NOT a datum.
Any given datum uses a specific spheroid (ellipsoid), but is also realized by a mathematical relationship to finite "POINTS." This becomes a particularly important when dealing with "ancient" datums, and the LOCAL realization of these old systems (monuments on the ground) are far more important than any mathematical whizbang theoretical relationship to modern geodetic datums.
Loyal
Loyal, post: 364455, member: 228 wrote: A spheroid (ellipsoid) is just a shape, NOT a datum.
Any given datum uses a specific spheroid (ellipsoid), but is also realized by a mathematical relationship to finite "POINTS." This becomes a particularly important when dealing with "ancient" datums, and the LOCAL realization of these old systems (monuments on the ground) are far more important than any mathematical whizbang theoretical relationship to modern geodetic datums.
Loyal
If I read you correct, Loyal, observing the actual locations of the town corner monuments would be superior to any attempt to estimate their locations using the ancient coordinates. Sounds right to me.
Unfortunately no conversion tool.
find some NGS stations close by that have USSD and NAD27 positions and inverse with the NGS geodetic tools to derive scale shift and rotation in vicinity.
Edit. Go Loyals route if the monuments exist.
Scott Zelenak, post: 364457, member: 327 wrote: Unfortunately no conversion tool.
find some NGS stations close by that have USSD and NAD27 positions and inverse with the NGS geodetic tools to derive scale shift and rotation in vicinity.Edit. Go Loyals route if the monuments exist.
That's an interesting technique, Scott.
Scott and Loyal are absolutely correct. NAD27 is not USSD. Here's a presentation on the history that Dave Doyle did:
Look at page 31 to see how big the changes are. Given that, I don't think you'll do too well with what I suggested.
Sorry I misled you.
Nice thing about USSD is you can inverse it in NGS toolsinverse because they share Clarke 1866.
Clarke 1866 is one of their choices.
Along with custom ellipsoids.
This thread is the clearest, simplest explanation of conversions, and locations, that has ever been posted on this site.
Thanks to all for keeping it simple!
MathTeacher, post: 364460, member: 7674 wrote: Scott and Loyal are absolutely correct. NAD27 is not USSD. Here's a presentation on the history that Dave Doyle did:
http://www.plso.org/Resources/Documents/Dave Doyle PLSO 2014 HISTORY OF GEODETIC DATUMS.pdf
Look at page 31 to see how big the changes are. Given that, I don't think you'll do too well with what I suggested.
Sorry I misled you.
Thanks for posting the link.
Big Al, you should contact MassDOT survey division to see if they have already done GPS observations on the town bounds. Over the years they have measured the NAD83 positions of a great number of the town corner bounds, as they are now the custodians of the records and are responsible for oversight of the maintenance done on them.
