5000,5000 with gps

[chan-geplease]

If you calibrate the base to a keyed in point of -5000,-5000,-328.08 it will get you back to 0,0,0 and you’re good to go….:-P

328.08…hmmmm That has a certain familiarity to it, doesn’t it.

[newtonsapple]

> We just started using a Trimble R6 gps receiver. On each job, it assigns a point number one to 5000,5000. This point is always about 300-325 miles to the southwest of our area. It always has an elevation of 328.08′.
>
> My question is, is the location of this point determined by the base station that we talk to, or is the coordinates of the base found compared to this point?
>
> I guess my real, quirky, question is, does 5000,5000 exist? Is there somewhere that is named 5000,5000 for all gps users to tap into?
>
> One of the reasons I ask is that I’m in Xenia, Ohio, and we are almost exactly between two base stations. Dayton is northwest of us and Washington Court House is southeast of us. There could be a time when we have two jobs next to each other and one day on one job we could be using WCH, and the next day on the other job we could be using the DAY base. In this case, will 5000,5000 be the same point when we merge the two surveys together?
>
> I know this is a fairless pointless question, but it’s been highly contested in the office here lately.
>
> Thanks!

5000,5000 is a very typical set of assumed coordinates, and 328.08 is equal to 100 meters.

Look in the project setup menu for a field along the lines of “first point”. There is usually a checkbox to select whether or not you wish a point to be created automatically upon project creation. Switch that off, and you’ll likely not see that point again.

And no, there is no place on Earth that I know of (in SPC or UTM) which corresponds to 5000,5000.

[ralph-perez]

That sounds more like a default data collector thing, I know TDS always defaults point number 1 to 1000, 1000, 100 (I think). The number 328.08 sounds eerily familiar though.:-)

Ralph

[jeremiahm]

So it really is a random point? Shux…

So it assigns a random point 300+ miles away, and then assigns coordinates to a base station based on that random point? This seems backwards since the base station should have a fixed, known location.

In order to give my points coordinates, it first has to set up the 5000,5000 point. How does it always give a point southwest of us that 5000,5000 point? Why not set 5000,5000 to the north of us at some point?

And, if that point is random, how do two survey coorelate? I used to think it’s because of both surveys using the fixed control point at the base station, but evidently that isn’t the case??

Gotcha on the 328. 😉 Duh…

[stephen-ward]

I assume that other state plane coordinate systems are like Tennessee in that they are set up intentionally so that both your northings and eastings are always large positive numbers. By definition 5000,5000 will always be generally to your southwest if your state plane coordinates are large positive numbers.

[spledeus]

i will guess it is just the job creation setting
our tds sets up a job with a 1,5000,5000,100,””
even though i often upload SPCS (not always, we have some old jobs on assumed)

you could setup a random starting point at 1,2700000,1700000,20,”RANDOM”
this would be a SPCS coord in Mass, local results may vary

[jeremiahm]

So, if I set up and do two different jobs allowing each job to assign a point in space this mystical 5000,5000. And these two job sites are only separated by a woven wire fence, what happens when I download both sets of points into CAD? Will the those random 5000,5000 points lay on top of each other, and the edge of each survey fall on the fence?

Yep, I’m no PS…

[chan-geplease]

You need a few common points from each project. This has nothing to do with GPS, but only about getting them both on the same datum. Rotate, translate, and/or scale as needed.

Have fun

PS – my first post was more of a jab, but I guess this is a serious question

[jeremiahm]

So you’re saying the answer to the above is “No, they won’t plot with the edges on the fence.”

The GPS/Data Collector knows where the base is that it’s getting its corrections from. So if indeed the answer is “no” it doesn’t set the point 5000,5000 off the location of that base, and it is random.

If they did plot each edge on the fence, that would prove that the assignment of 5000,5000 isn’t random, but it actually gets plotted according to the location of the base.

Does this make sense?

[ralph-perez]

Two Questions
What State are you in?
What type of Projection are you working with?

I personally believe this is just a random default setting in your data collector.
You normally would have to add a million or more to come up with false Eastings and Northings, so 5000, 5000 is not a realistic SPC value.

Ralph

[chan-geplease]

Without trying to become flippant, what part of “You need a few common points from each project” seems troublesome. That is about as fundamental to CAD and mapping as it gets. Not to mention it’s just SOP to any surveyor type, PLS or not.

Another thing I would be suspect about is the 328.08. Check your units. My guess is they are metric, which may bother some people. Trimble is famous for wanting the world to be metric, and betcha your data collector default is. Change it in “Survey Styles”, I think.

Like I said, have fun…. and good luck

[kris-morgan]

I think someone in the office keyed in a value of 5k,5k for point 1. I assume you’re working on the grid (state plane coordinates) and it’s a bunk value. Point 1 doesn’t exist if you’re working on the grid, ever. I can’t begin to start on how all of this is going, but my guess is you’re on the grid and some dumba$$ in the office (or field) thinks they know better.

[cliff-mugnier]

Since some people are used to X,Y coordinates and some people are used to Northing, Easting coordinates, 5000,5000 is an awful habit of assigning false coordinates to a project just to avoid negative coordinate components.

I have my students assign false coordinates so that one component always has a different number of digits to the left of the decimal point (e.g. 15000,5000). That way there is never any confusion as to what is X,Y or Northing, Easting in a given project.

[ralph-perez]

You could be using ECEF and it would put you

Near the intersection of the Prime Meridian and the Equator, almost at the Earth’s Core.

[foggyidea]

5000,5000 with gps>Cliff

that’s funny, I’ve been making that same argument for the past 30 years. I always start with 5000, 10000, and assume an elevation of 200. But my projects are smaller, and I rarely have one over 1000′ square….and elevations here don’t go much over 100′ except in a few places.

I never could understand why someone would want to use units that are so close to each other. But then again, I do hark back to the days of field calculations and older calculators..

[jerrys]

Sounds like you are using Survey Pro and that 5000,5000 point is the default point from when you start the job.

[MightyMoe]

I would figure all this out right away. It would be a good idea to see just what your projection parameters are doing to your work. It’s a good idea to print out the Coordinate System details (metadata) for each job and put them in the file.

Each job is getting put into the same projection and that’s great-as long as the projection does a good job covering the area you are working in. What you don’t want is to get a good distance from your projection origin longitude, origin latitude. You may well be working at sea level. That might be fine in Ohio but you should at least know if there is a scale factor in the projection-that you will see in the Coordinate System details

It won’t make any difference which base you use (a better idea is to use both of them each time and adjust each set-up or send it to OPUS and let them do it). The projection will stay the same and 5000, 5000 will be attached to a lat long. Now, how well the two bases (CORS stations?) are surveyed to each other will matter, but if they are cors then they should be OK. You do need to pay attention to the EPOCH for each station.

[jeremiahm]

“Flippant,” what a great word! I’m going to have to remember that one. I’m “flippant” with the guys in the office around the water cooler right now. ha ha

This gps stuff is totally new to me. We’ve only had it for about a month now, and as you can tell, we know just enough to be incredibly dangerous…

So, when surveying with old equipment, we set up our first point as the point under the gun, and assigned 5000,5000 to that point and then took all of our side shots from there, or shot in the next information point. 5000,5000 in that case is easy.

Now, we pull into a field and we have Scotty beam us up. We connect to the Ohio CORS system, and then start taking shots. We do put 5000,5000 into the data collector, or at least we did the first time we set up the defaults. It throws that first point 316 miles to the soutwest of us. Makes sense that its sw of us, based on the coordinate system and that we want to be positive in both directions. Our “backsights” in this situation is a base station in either Dayton or WCH and a whole bunch of satellites overhead. If we stop the survey, end survey, then come back the next day to start up again collecting data in the same field, all we do is “beam me up” again and connect CORS and start taking shots. There aren’t any field shots we need to take to check our work, but we do anyways. We’ve never had a problem with the new stuff lining up with the previous stuff. So, the only other mapping points we are counting on is the satellites and the base station.

So, why the heck does it throw 5000,5000 in a spot that is who knows where, other than the fact that it’s far from us, and there isn’t any worries about getting shots less than 5000 in either direction.

I think this is a “chicken or the egg” type of argument. I think the base comes first, then it builds a 5000,5000 point off the coordinates of the base. I don’t think that it randomly assigns a 5000,5000, to a point “somewhere” and then gives that known location base station coordinates based on its random assigning of point 1.

Since this thinking goes against everything that I know of surveying up to this point, and with this equipment, that’s why I’m asking this very basic, very stupid, very quirky question. No need to get “flippant” about anything. 😉

I’m trying to learn all I can about this equipment, and how it works, in order to get better data in the field. You’ve all been very helpful up to this point!

[MightyMoe]

I THINK I see what’s happening. You are probably on a state plane system and the 5000, 5000 point SHOULD be SW of you. This is something you really need to know.

Once you have a control point you shouldn’t need to keep connecting to a Cors station. Just hold the coordinates that you have for the set-up point once it’s established. You can collect data to check the point, but you should be good to go when you set-up on that point. I’d give up on the 5000, 5000 idea and let the projection tell you what coordinate you are at. Really, you should figure out what the coordinate system is, if nothing else when you reference a basis of bearings it would be nice to find out what that basis is.

Things can get really strange and twisted if you are trying to use a local projection from far away.

[ralph-perez]

So, why the heck does it throw 5000,5000 in a spot that is who knows where, other than the fact that it’s far from us, and there isn’t any worries about getting shots less than 5000 in either direction.

I think this is a “chicken or the egg” type of argument. I think the base comes first, then it builds a 5000,5000 point off the coordinates of the base. I don’t think that it randomly assigns a 5000,5000, to a point “somewhere” and then gives that known location base station coordinates based on its random assigning of point 1.

Since this thinking goes against everything that I know of surveying up to this point, and with this equipment, that’s why I’m asking this very basic, very stupid, very quirky question. No need to get “flippant” about anything. 😉

I’m trying to learn all I can about this equipment, and how it works, in order to get better data in the field. You’ve all been very helpful up to this point!

I don’t think you fully understand this yet. Check your setup and find out what system your working in (i.e State Plane etc.),then check your project parameters. Now, look and see what the point number is for 5000, 5000, 320.08, I bet you’ll find that the base station has nothing to do with any of this. That 5000, 5000 point is just out there. It’s a figment of your data collector’s imagination. (I can’t really say that for sure).

Now, by the tone of this post, it appears like you’re just starting out your Surveying Career or you work for some Engineering or Gis outfit that’s trying to utilize GPS. It might be a good idea for your firm to invest in some training. It’s a good thing to ask questions and you’ll probably learn something from the responses.
Hang in there, Don’t leave before the miracle

Ralph