OPUS- Antenna height is not a decimal number

I'm not sure I have the answer, but what is your antennae height?

Ralph

1.54 m. Although the elevation is not important on this job, so I will take anything.

> 1.54 m. Although the elevation is not important on this job, so I will take anything.

I imagine you're experienced user. I would try it again, it's probably something silly like a typo or the program is acting up.

Ralph

Just tried it with your height and it gave same error.

I use a fixed height rod at 2.0 meters and it works.

So I put in your height as 1.5 and it worked.

It appears to be a number of spots after the decimal issue. That seems odd as there may be many users that don't use a fixed height rod and would need the extra decimal places.

Of course the accuracies on vertical to be expected may lead to using only on place after the decimal.

That worked! Amazing, as I am nearly positinve I have used 2 decimals before. Guess that will be a battle for another day.

Thank You very much.

I use 1.982m every time...never had an issue...could just be a temporary OPUS glitch.

2.146 Here, Never Kicked Back

Maybe some unseen character in your entry. Are you sure it is a period you are using and do not add the "m".

Paul in PA

That is good to know.

I thought it would be odd that someone using a tripod and tribrach to mount their receiver would be limited on the number of decimal places. It sure would throw the vertical component right out the door.

I've been told that an incorrect height can affect your horizontal position and to always have it entered in correctly.

OPUS emailed me back and reported that the problem had been fixed.

Thanks to everyone.

Wlt

[sarcasm]Really?[/sarcasm]

Incorrect Antenna Height Affects Post Processing

If you occupy a point twice and for one occupation the antenna height is wrong it can throw off horizontal positions far away. The post processor tries to resolve the two different elevations and can warp the whole least squares adjustment.

I learned that the hard way on one of my first GPS jobs establishing control over more than 100 acres.

Because every OPUS solution is independant of others, you just end up with different elevations on the point in question.

Paul in PA

I do everything 3D.

We are Surveyors, we measure things, measuring heights is fundamental.

I haven't found a flat Forest survey yet. Height is a necessary component.

Incorrect Antenna Height Affects Post Processing

Yes - did you see the [sarcasm]sarcasm[/sarcasm] font?

What a great number of folks (who only know where the power button is on their units) don't seem to understand is that GPS measures locations in the ITRF, a 3-d grid. Every point has an x, y and z value in this system first, and then the conversion to SPCS (or whatever) occurs. If the antenna height is incorrect, of course the position will be wrong. If the wrong position is used in an adjustment it will in one way or another propagate through and affect every point in the network. If the software is worth anything, and the data processor knows how to interpret the results they will see this.

What I am getting at is that very few users seem to know what they are doing...

Incorrect Antenna Height Affects Post Processing

I try to explain that GPS is NOT a plane measuring device.

Shoot, even my Total Station is not a plane measuring device. Every setup has a slightly different plumb line.

I measure heights for everything because that is what I do; measure things.

Incorrect Antenna Height Affects Post Processing

>Every point has an x, y and z value in this system first, and then the conversion to SPCS (or whatever) occurs. If the antenna height is incorrect, of course the position will be wrong.

I still don't buy the argument. Yes, it first calculates x, y, z. It gets the actual position of the antenna. Then it uses the antenna height you gave it to calculate the position of the point the antenna is over, using the normal direction to the ellipsoid. The antenna position, the calculated point, and the true point you are attempting to measure all have the same lat-lon or SPC.

Of course your local vertical is not identical with the normal to the ellipsoid, but you are ignoring that fact for any GPS measurement and it is insignificant over a few feet of antenna height.

I can see that 3D fitting would have some problems due to the wrong elevation.

"a temporary OPUS glitch"

Am I the only one that this makes uncomfortable?

Least Squares Adjustment Of XYZ Points

I am fairly certain the LS adjustment is of the ground points, therefore the same? point on the ground would have different XYZ values with one wrong antenna height. I also believe the LS adjustment is of all the X's all the Y's and all the Z's. To force the same? point together all values of other points change, X, Y and Z changing Lat and Lon along with Elev.

For those that do not use fixed height rods, different antenna heights should yield the same ground XYZ day to day. In fact I have reoccupied points that I was not initially happy with by adding an extension to a fixed height rod to improve the sky view.

OPUS calculate the XYZ of the antenna because it has a base of all CORS antenna XYZ pointsd, then reports XYZ of the ground point. Then a wrong elevation just gives a different elevation. From my observations that is not the case in Post Processing software.

Paul in PA

Least Squares Adjustment Of XYZ Points

Yes, that is right.

The baselines or vectors are reduced down to the top of the monument or control point and adjusted. If you disregard heights it could throw a major wrench into your results.