Thank you MightyMo!
If you are surveying in 'Nevada State Plane' then you ARE NOT 'on ground. NDOT uses a Las Vegas Valley Mean Combined Scale factor of 0.000177 to go from grid to ground (up). That equates to 0.168' in your "950 feet". This appears to be your issue. You are only in State Plane when you are on the grid. You cannot mix surface measurements with State Plane, you are either on the grid (State Plane) or not. I have no idea who you are working for, but this can be a MAJOR issue if you do not comprehend the difference between grid and ground.
Moe is spot on regarding truncating coordinates to make ground coordinates obviously distinguishable from true State Plane coordinates. If you are working on a construction site you had better be operating on ground. Plans in Clark County are required to contain a Ground Control Plan. Frequently they are only one sheet and should be amongst the first few sheets in the set. That sheet should contain local coordinates and if a scale factor was used to obtain ground distances from State Plane, it should be included on this sheet. Also, the coordinate base point for the scaling should be included. I have found this to be overlooked or not provided on several occasions and it is extremely annoying and unprofessional to neglect to provide it. I believe it reflects a lack of knowledge by those who do this dastardly deed. I like using a base scale point of North 0.0, East 0.0, for good reasons. Also any coordinate transformations such as truncating should be included as Moe suggested: Northing – 26,000,000.00 East -700,000.00.
All that nice control done in 2015, then someone comes along and sets up SPC and designs from that, but the design is ground (pretty sure), control is grid. SIGH!!!! (Push that button, get that number)
When facilities get large enough grid-ground becomes an issue. Designing 3000' below ground is problematic. Most items like parking lots, roads, curb and gutter, pipes aren't materially affected by 150ppm, but when there are big buildings, bridges, large structures, tight setbacks, it must get dicey, I've never built anything using state plane, we usually start around 250ppm and get larger scales, so no local engineer ever wanted to deal with that. I did have a railroad demand SP in central Montana at 750ppm, that was very interesting, it never got constructed since the project fell apart during the land acquisition phase.
Friends don't let friends convert grid to ground without truncating.
P.s I miss the thumbs up options
For the 80th posting to this thread I'd like to crow about the low-distortion zones system in Oregon called the Oregon Coordinate Reference System (OCRS). These scaling issues just don't exist when using the OCRS. Yet too many people insist on continuing to F' around with scaling state plane. Arrrgh!
👍
Amen. Go low distortion or go home.
Custom projections just aren't a problem any more with industry-standard sofware.
The thumbs up option is only available when viewing from the activity thread. A very odd structure indeed.
It's extremely common that grid to ground coordinates are not truncated in every area we work. Haven't ran into any issues yet. The only issues we run into is when the original surveyor can't adequately explain their project datum in a clear and efficient manner....which is why we try very hard to not ever be in that position.
Just to be clear about prism constants using a Leica TS......you wrote that you "checked the prism constant" but if you are using a Leica prism and select it from the list then the prism constant is set for you, you cannot change it. If you use any other non-Leica prism you must create a custom prism in the list with the correct constant for that prism. If you use a standard non-Leica round 30mm prism and select the Leica standard round prism from the list you will measure 0.10' long (too much) on every shot because the Leica prism is preset at 0mm.
Edit: I just saw your post on "My New Setup" and that looks like a non-Leica prism so I would check some short TS shots with a tape.
More exactly, the number is 34.4 mm = 0.113 ft, not 0.1 ft.
If you use a non Leica prism and tell the instrument it is a similar Leica, the difference should be minor.
If you tell the Leica instrument it is a -30 mm prism, then yes, you are off a bunch.
So true.
You are correct. I set 2 points 10.00' apart on my level driveway. Used my Leica TS15 and a Leica round prism on a tripod with a tribrach and measured 10.000'. Popped off the Leica prism and set a Sokkia round 0.30mm prism and measured 9.991' using the same Leica round prism selection from the list. But I do not know why the Sokkia measured short. The Leica is -34.4mm and the Sokkia is -30.0mm. It should have measured 10.014' right? No?
Edit: Thought about it some more and the Leica applied a -34.4mm constant to a 30mm shot making it 0.014' shorter at 9.99'.
So to add some Closure to this bust. I called the survey company out on the bust of 0.15' on the control.
They came out reshot it and said yes there is a problem, (I watched as they did a resection ) Then they came out the next day with a different gun. Attached is a text from the Manager
They sent me the new control, I set up on the new control and did my backsight, and was was .006' at a 930' shot. and checked in on another control and was good there also. Then went to all the batter boards that they set grid lines on and I was 0.01 or better on every grid line shot. This is on a scale factor of 1.00000 and Yes I have a Leica round a Leica 360 prism and one SECO -30mm. The SECO is the only prism I have to make in the prism selection tree. You put in the -30mm in the absolute section and the software calcs out what it needs to be.
Damn. That text from the manager...wow. It ain't as if SPCS is new or anything.
