Leica CS 15 GPS and TPS data

Set up a big square shape 500 m by 500m at your local airport and gps to robot grid to ground
visa versa push all the grid ground toggles on your DC soft system other than that
budget a day or two to see what the softs are doing.

It is really that simple test the soft. test soft again until you have headache
repeat as required..

I'm assuming you are working in state plane grid format on the gps? The GPS native coordinate system (what the data is recorded in) is WGS84 and the total station is recorded in local grid coordinates. I have only worked with system 1200 gps and tps and a cs12 gps, but I would imagine using the equivalent total station would work somewhat the same. You load the state plane coordinate system that you will be using into the gps and total station in leica geo office. If you start the job in the gps (specifying the state plane grid) and load the same job into the total station, it should automatically be specified as state plane. If you are manually inputting the station point/backsight then you will have to specify state plane when you set up the job. It's pretty seamless.

We use CS15, GS14 and TS15. We use both GPS and TPS on most of our projects.

The GPS Coordinates are in whatever coordinate system you are using...could be grid or ground based coords.

The TS shoots grounds distances and doesn't do any kind of automatic scaling. (unless there is some option that I've never found)

Smartworx gives you the option to set the scale factor in the TPS. I've never used that option so I've never looked to see if VIVA has the same thing.

All GNSS data is referenced to and stored in WGS84 in either cartesion or geodetic values. When you choose a coordinate system for the project the data collector simply applies the proper transformation and projection on the fly to provide you with the data you want to see. Assuming that you are collecting your TPS and GNSS data in the same file or at a minimum both files use the same coordinate system, then the the CS will the same projection parameters to calculate the scale factor each instrument stations. The software then applies this correction to each shot and the resulting coordinates are grid. In Smartworks you can manually override the computed scale factor for TPS shots and this would definitely cause some problems.

I use this ability on about 95% of my project work. It is really nice when combined with low distortion projects. I will state though that I am still using 1200 systems and not Viva as yourself. But Viva is basically Smartworks with a glitzy interface.

John

John,

You can have the TPS scale your TPS coords down to grid, but you can't have it automatically scale your grid GPS coords up to ground.

It sounds like he is trying to make sure all his points are on the ground.

"It is really nice when combined with low distortion projects."

Isn't the whole point of a LDP is that grid = ground (or pretty close) and there is no need mess with scale factors???

Beavers,

Yes the LDP does minimize the distortion of the projection but they still have a scale factor associated with each discrete point. The procedures I mentioned are standard operating procedures anytime you are working on the grid with ground instrumentation. unless you purposely change the setting int the DC it will scale the ground distances to selected projection.

You can actually scale the GNSS grid values up or down to ground if you perform a site calibration through 'Maps & Datums' in LGO or the related program on the DC.

> Beavers,
>
> Yes the LDP does minimize the distortion of the projection but they still have a scale factor associated with each discrete point. The procedures I mentioned are standard operating procedures anytime you are working on the grid with ground instrumentation. unless you purposely change the setting int the DC it will scale the ground distances to selected projection.
>

I didn't know that the software would do that...learned something new today.

I always just leave our scale factor set to 1.0000 in the gun. (1203 w/smartworx)

So if I have the GeoPPM calc scale set to automatic and I have my coordinate system set to a SPC zone in the TPS then is it going to automatically scale the TPS measurements to grid and not actually give a ground distance?

SurveyNJ,

I am a big fan of having apple to apples with my coordinates. Both System1200 and Viva SmartWorx will handle this easily if you have a defined coordinates system. I can describe Viva SmartWorx procedure as this:

1. When you create a job (TPS side or GPS side) make sure that you tag a coordinate system

2. On the GPS side everything will be converted from WGS84 to your coordinate system… no problem

3. On the TPS side make sure you have the coordinate system as part of the job properties. This will be automatic if you started the job on the GPS side. I am just saying to check it.

4. Next page over to the TPS Scale settings page and set the Compute scale using: Stn & coord system. This setting is saved as part of your job

5. The system will now use the coordinates of the control point that you setup the instrument over and compute the scale factor in your coordinate system for the position of your control point being used for the setup. So the scale factor used will be recomputed each time you use the Setup application over a different control point.

This way you have apples and apples, You will have both GPS and TPS measurements scaled in your coordinate system. You can also use a manually inputted scale factor if you use the SF/GeoPPM option in the TPS Scale page under your job properties. You simply enter your site scale factor in the User entered scale factor: field under this option.

I am explaining it this way to keep all the coordinates generated in the CS15 to be on the grid of the coordinate system being used. If you want to convert to ground you can do this in the office later for example. All of the TPS measurements stored (Horiz Angle, Vertical Angle, and Slope Distance) are all plain-jane raw measurements.

g'day SurveyNJ,

surveythemark has it.

if you are recording to the same job, and you allow the TPS to scale the measurements based on the computed scale factor for that station and it's grid coordinate system, then they will play happily on the same job and your measurements will gel together within the expected accuracy of each measurement. mix and match TPS and GPS measurements happily.

Thanks for all the replies. This clears it up for me. Not sure how I feel about working in grid cords with all my TS data. We do a lot of work that ends up being used for design then construction layout. If you guys collect everything in grid are you processing in LGO to ground prior to any mapping? Would you then use the ground coordinates for the remaining duration of the project? Layout etc?

As long as you have stated that your survey is referenced to that coordinate system (e.g. Bearings and Coordinates are referenced to State Plane Coordinate System), it seems like it shouldn't cause any problem for design or construction layout. Especially in this day and age where contractors are also using GPS for staking and machine control. But it would depend on what your client needs. You could just work in local coordinates with the total station for a small building stake out.