Conversion Help Needed

[+frex3wv]

Hi Everyone - it has been forever since I posted here - I hope everyone is doing well.

 

Years ago I searched for a 60+ year old USGS disc to no avail.  The property is now under construction and so I called the Project Manager and he told me they HAD located the monument!

He gave me coordinates - BUT - I need them translated into what I am familiar with when geocaching (N XX.XX.XXX  W XXX.XX.XXX)

 

Can anyone do the conversion I need?

 

Here is what they gave me as coordinates: 489442.66424,1777589.00865,873.11600

 

Thanks in advance!

 

David

[CallawayMT]

Those appear to be state plane coordinates.  They can be converted, but I would need to know a general location for your monument which would help with the state and zone needed to convert them.

 

CallawayMT

[+frex3wv]

Charleston, WV

 

[CallawayMT]

Here is your conversion complements of NGS.  The upper Lat Lon Numbers are in Degrees and the lower Lat Lon numbers are in DMS.SS.  Assumptions based on your location are WV state plane US Feet due to state unit statute and zone based on your location.  If it hits where you expected, we guessed right.

Edited December 14, 2018 by CallawayMT

[Bill93]

And in case you aren't familiar with converting to DD mm.mmm format, from Callaway's post I calculate

N38 20.534 W0 81 39.940

 

That should get you in the neighborhood.  Since the surveyor didn't give you the "metadata" that tells what his numbers mean, there's a bit of uncertainty.  He was probably working in NAD83, and your handheld (unless newer ones have improved the conversion) is in WGS84 even if you tell it you want NAD83, so there's a meter or two difference there.

 

And the biggie is whether those coordinates are true state plane.  Since state plane is near the elevation of the ellipsoid model of the earth, and there is distortion in flattening a piece of earth to a plane map, distances between two points on the surface are usually longer than the difference in state plane coordinates.  To band-aid this and allow people to work in ground distances, some people scale the SPC values to get coordinates in ground distances.  When they do this, they need to specify exactly what scaling was used so that others can follow the process, but this isn't always made clear.  IF this was done to the coordinates you have, they could be off 200 ft.  In that case try N38 20 31.520  W081 39 58.786 (N38 20.525  W081 39.980).

 

On Google Earth, the first coordinates are between the NW corner of a parking lot and the house to its WNW.  The second set are SSW of that house toward the road.

Edited December 15, 2018 by Bill93

[Bill93]

I agree with Calloway that his coordinates are most likely.

 

He pointed out to me that my alternate coords, with technicalities most people won't care to figure out, are the third most likely scenario.

 

The second most likely is a local scaling about some project point that would give answers so close to the first method that the difference won't show up on a recreational GPS.