Not 1000, 1000, 1000
I always wondered what the problem is with negative coordinates? Maybe Paul can explain....
I have seen several coordinate systems with negative numbers, never been a problem. One important system that comes to mind is the Bogart system in northern NJ and on Staten Island.
I wrote a program years ago to compute coordinates on the Bogart system from NAD27 Lat/longs...it was very easy because it was a simple tangent system with 0,0 at triangulation station BOGART
> Since this is your first rodeo, I'd highly recommend booking this traverse and logging the measured distances. Apply the scale factors later. If you make a mistake in application of the scale factor (very easy to do) at least you will have your original measurements.
Do most post processing software (none of which I have) enable you to apply scale factors leg by leg?
If so, are scale factors "known" to the software, given the elevation and long/lat of the leg, or does one enter them manually?
Are scale factors applied to ONLY horizontal distances between two marks (as read on the TS)?
> Do most post processing software (none of which I have) enable you to apply scale factors leg by leg?
Most that I am aware of. Yes.
> If so, are scale factors "known" to the software, given the elevation and long/lat of the leg, or does one enter them manually?
>
Yes. These are computed by the software. You will do well to keep up with instrument heights, prism heights, zenith angles, and slope distances in the book. This way the elevations can be determined from your measurements.
> Are scale factors applied to ONLY horizontal distances between two marks (as read on the TS)?
Yes. In theory the average of the combined factor at the instrument and the combined factor at the prism are multiplied times the horizontal distance to get the grid distance. If the elevation difference isn't substantial, the combined factor at the instrument should be fine.
Not 1000, 1000, 1000
some old grids I've looked at were in northing/westing format, they are basically lats and longs reduced to coordinates, they are fun to imput into autocad;-)
>
> Yes. In theory the average of the combined factor at the instrument and the combined factor at the prism are multiplied times the horizontal distance to get the grid distance. If the elevation difference isn't substantial, the combined factor at the instrument should be fine.
Perfect. Seems like easy enough math to do manually. One more follow up question please. Is there a "scale factor" calculator at the NGS site that will tell you scale factors for any Lat/Long?
Alternatively, If I have the Elevation factor for two benchmarks "x" feet different in elevation, can I scale the elevation factor to apply to setups/prism locations?
Similarly, if I have the Scale Factor (the other component of the combined factor shown on NGS data sheets), can I scale that one according to the longitude of the setup?
> Long traverses, or tying to State Plane Grids?
I refer to properly tying into State Plane or other projections and properly applying scale factors convergence angles.
> Traversing between them would likely tell me how good I did, would it not? I won't kid myself about possible results. This won't be any Yolo Baseline for sure, but it might be a start.:-)
Maybe, if the 2 benchmarks in question are of similar high quality. Not all benchmarks have high quality horizontal coordinates. Not all have high quality elevations. Examine the appropriate data sheets carefully to determine just what your benchmarks have.
> >
>
> But what if I find TWO Benchmarks, both of excellent quality, perhaps both even accessible in the winter, and both with known State Plane Grid coordinates, a few miles apart? Other than the marks themselves, I don't even need to see the dirt...I'd be using prisms on tripods.
>
> Traversing between them would likely tell me how good I did, would it not? I won't kid myself about possible results. This won't be any Yolo Baseline for sure, but it might be a start.:-)
Take a look at LOCUST 2011, RTE 12 BARNARD 1996, and RTE 12 BARNARD AZ MK 2011. These might fit the bill for your practice traverse.
DDSM:beer:
> > >
> >
> > But what if I find TWO Benchmarks, both of excellent quality, perhaps both even accessible in the winter, and both with known State Plane Grid coordinates, a few miles apart? Other than the marks themselves, I don't even need to see the dirt...I'd be using prisms on tripods.
> >
> > Traversing between them would likely tell me how good I did, would it not? I won't kid myself about possible results. This won't be any Yolo Baseline for sure, but it might be a start.:-)
>
>
> Take a look at LOCUST 2011, RTE 12 BARNARD 1996, and RTE 12 BARNARD AZ MK 2011. These might fit the bill for your practice traverse.
>
> DDSM:beer:
These are the ones I'm looking at: AE6516 and AA8188. It's about 2.5 miles, Long sights, around 120' difference in elevation. And A8188 is on a bridge abutment, so I'm sure I won't have any trouble finding that one, lol.
As for accuracy, I'm still learning how to read the data sheets regarding "network" vs. "median local accuracy" , but they're showing what looks like less than 2 cm with a 95% confidence. Does that mean that if my Star*net-ed adjustment of the traverse at 95% comes in closer than that, I've done ok?
Bottom line though: are these high enough quality for my purposes?
> These are the ones I'm looking at: AE6516 and AA8188.
AE6516 aka "206 VT 102"; AA8188 aka "Gulf Stream"
