Trimble Survey Controller Grid to Ground

I think I know what you are asking, it's not scaled from anywhere.

Say during an inverse in COGO you can set the distance to read ground or grid. The grid distance is an inverse of the grid coordinates, the ground distance is computed for the actual ground measurement.

It isn't going through a scale factor and re-calculating the ground distance from a recomputed set of XYZ coordinates.?ÿ

For my topo job last week the inverse from my base to a random topo point is 16,269.22' grid, 16296.29' ground. The grid is an LDP already set-up to closely match ground distances. A file for the same area using SPC would result in a smaller grid distance but the same ground distance. Basically the DC scales the projection how you tell it to, from where you tell it to and will always be able to inverse a ground distance.?ÿ

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If you go into jobs window and click properties of job, then coordinate system. if you choose selected from library for state plane then on the 2nd screen you can define the scale factor 3 different ways.?ÿ ?ÿThe manual or help section can give you a better definition of this but basically you can put in a scale factor.

However, once you do a calibration to ground coordinates, the ground and ellipsoid distances no longer have any meaning.

The local geographic coordinates are changed and those inverses are no longer valid.?ÿ

If you have selected a predefined system, you appear to be asking about 'local site settings'. This is where many people choose to set a scale factor and origin to bring the project to nominal ground.?ÿ

There is (was?) a glitch in Access for awhile that would not allow scaling from 0,0. It would add some hundredths or even feet to the northing. Not sure if that has been fixed, but it was irritating...

Thanks for the explanation about the LDP Mo....Let me clarify....If we set up a project in State Plane, collected data and then wanted to bring to ground using a calculated scale factor scaling from 0,0.

Project Settings >Coordinate System>Key in Parameters>Projection>2nd Page,elect Ground(keyed in scale factor) enter scale>3rd page, elect Grid cords, Northing: 0, Easting: 0?ÿ Height?

False Northing offset: 0?ÿ False Easting offset: 0

Are those the correct settings?

Bionicman, if there is a glitch, is it better to download your grid file into C3D, then scale from 0,0 by your scale factor, download back into DC with new job within a Local Site.?ÿ

In Project Location> 3rd Page, Lat Long is blank, enter Height>4th page False Northing, Easting set to 0???

Scot, found 2nd screen, same as shown above, from Library...to scale from 0,0 what needs to be entered on 2nd and 3rd page?

That would be one fix. I prefer to do any manipulation prior to cad.

My permanent fix was to leave the private sector. So far it has worked consistently well... ????

What you are asking is how to set-up ground coordinates. You can pick whatever point you wish to scale from typing in the N E numbers, if you want 0,0 use that, but be in control yourself and chose what number you want, then put in your scale factor. In Trimble you want to use a number greater than 1, in C3D the scale will be the compliment.?ÿ

If you use 0,0 it will be simpler to go back and forth between the coordinate systems, it's usually how DOT does it.

There are no correct settings in that screen, it's the settings you want and you need to set what you want for the reasons you wish to have them set that way.?ÿ

Posted by: rlshound

Scot, found 2nd screen, same as shown above, from Library...to scale from 0,0 what needs to be entered on 2nd and 3rd page?

I'm sure you have a reason for going from 0,0.?ÿ ?ÿI tried to avoid that for multiple of my own reasons.?ÿ ?ÿYou could do it that way.?ÿ ?ÿI set the location to be near the site and I mostly use where I setup my base.?ÿ ?ÿTypically in the middle of the project if possible.?ÿ ?ÿSometimes I will use a found NGS marker.

Local site setting at 0,0 using state plane coordinates

Inverse showing the grid vs ground with a scale factor applied

Using the trimble local site setting the grid vs ground should be very close, if not adjust your scale.

Find the latitude and longitude that would correspond to the coordinates North 0.00 and East 0.00 then enter that latitude and longitude into the last screen you show. When you change the scale factor, your coordinates will change based on scaling from 0,0

If it was Texas, I could send you my template file.

James

First, are you matching into someone else's data or setting your own? Where did you get your scale factor from? Most determine this by setting a initial point on site in Grid, then using that point to let Trimble calculate the scale factor. Then if you want to keep your project looking like it is grid, but measuring in ground distances apply the scale factor you got and base the coordinates on your grid point location, typically your basepoint. If you're working in "datum adjusted" like most US DOT do, then once you have your grid point, use it to calculate your scale then set the origin to 0,0. Scalle does nothing to elevations. It is only to distances. I always go ground. The process is simple and always the same. Doesn't matter if yourey starting your project or going out to do layout. Most states require you to be on ground. You can scale it later in cad, but then you're doing it different when you go back out to do layout or pickup more data. I like starting and staying on ground at all times for this reason. If you do that and have to go to datum adjusted for DOT use later it is a simple translation.?ÿ