Hello dears
What are the acceptable values for the variance ratio
When I read the report note
Can you help me to get a book explaining the specifications of the survey works?
best regards
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The variance is a statically analysis of how far each number used in the calculations is from the mean.?ÿ
0 would be a prefect #, there can be no negative #.?ÿ
As you can see the larger the variance # the smaller the RMS #, which seems counterintuitive.
There are a number of resources that can help you understand the formulas used to calculate the variance.?ÿ
I would suggest a google search, others here may have a good website to suggest better than I will know offhand.?ÿ
I don't think it is a simple variance of the observed values.?ÿ Variance should increase with RMS (variance is RMS squared if zero mean). It seems to be a ratio of that variance to something else, which I haven't identified.
What software is this?
I suspect the variance is not your primary problem with this data. Am I interpreting the delta Z value correctly?ÿ to indicate that there is more than 23,000 vertical feet difference between 2 of your points? Or more than 7400 meters?
Am I interpreting the delta Z value correctly?ÿ to indicate that there is more than 23,000 vertical feet difference between 2 of your points? Or more than 7400 meters?
Those are likely ECEF coordinates rather than plane coordinates.
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Perhaps the Variance Ratio refers to the F distribution?
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Dear brothers, the results of the calculations are clear. Are there any comments about the results? Please help
Should have said delta values rather than coordinates.
ECEF is a Cartesian coordinate system, is it not?
I only intended to point out that the origin of the coordinates shown (actually vector components) were not Earth Centered Earth Fixed.?ÿ
pedantically,
DMM
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were not Earth Centered Earth Fixed
what is mean that please
the orgenal point fixed from opus site
?ÿis there error in work
ECEF coordinates are 3D Cartesian coordinates whose [0;0;0] XYZ coordinates are with respect to the center of Earth mass.?ÿ
A latitude, longitude and ellipsoid height can be transformed into ECEF XYZ (and vice versa). One can also transform between reference frames and epochs. The screen capture below shows the output of a tool on the NGS site transforming between NAD and ITRF. Note both geodetic and XYZ coordinates are shown.?ÿ
As I am unfamiliar with the software you use, I have been hesitant to comment. I do not see in your output the vector residuals. This is a comparison of the computed minus the observed measurements. Your images show the (computed?) vector components (DX, DY, DZ) but not how these components compare with the observed vector components.
Your postings seem to indicate a desire for assistance in understanding how to determine whether you have a good result. For me, the overall statistics (rms, variance of unit weight, degrees of freedom, etc) are important but only after a thorough analysis of variances.?ÿ
Also critical is whether your work satisfies the standards and specifications for the project. For example, even though my statistics might indicate a good result, it will not satisfy requirements for redundancy, equipment, modeling, etc.
An example of some of the statistics used in the analysis of a GPS project are shown below. Not that the two blocks show first a minimally constrained or ??free? adjustment and a final constrained adjustment. In brief, the first allows analysis of your work; the latter allows analysis of how your projects fits into a larger network.
HTH,
DMM
@sadiq-muhammed And the answer is NO I was not interpreting them correctly.
A good graphic showing the relationship of ECEF (XYZ) and latitude, longitude and ellipsoid height. This site allows you to do the transformations. Site address is: geodesy.noaa.gov/TOOLS/XYZ/XYZ.html.
If you need to know if your data is good, find out if it's repeatable. There is no way to tell otherwise.?ÿ
When GPS was nascent at an early "how to" seminar (NGS) the presenter showed slides of ECEF, lat-lon el, and State plane coord systems.?ÿ He then turned off the projector and asked us all to point in the direction of the Z value in ECEF and we all pointed straight up as Z is elevation.?ÿ Wrong!?ÿ At the equator Z points directly north and at the north pole it points straight up.?ÿ He pointed about north 30?ø below the zenith for Z at our latitude.?ÿ He then went into how ECEF GPS coords are transformed to lat-lon el or SPC and the complications of Geoid models, gravimetric considerations for terrestrial observations and how accurate GPS survey observations are based on translocation from nearby "correct" control stations.
Quite an eye opener for me.?ÿ Keep in mind an an autonomous GPS receiver even if dual frequency has an RMS accuracy at best of +-1 meter location and maybe 2m vertical.?ÿ "Autonomous" means no correction signal reception or post processing after the fact translocation.
Dear brothers
thank you very much for all the comments .............
I am a beginner in this work. Please a simple answer regarding my project. Is it acceptable or not?
I don't see anything that jumps out about your data. The issue for me is it's one observation.
Do it again and then you will know.
Use different procedures to eliminate as much error as possible. Measure your H.I. to different points on the antenna, use feet as a measurement one time, meters the next. Be sure the tribrach or bubble is facing a different direction each time. Mix antennas and tribrachs if possible.?ÿ
However, from the data posted I'm assuming you are using a single receiver and occupying each point with it so multiple?ÿ receivers won't be possible.?ÿ
The exact 15 minute file length suggests that it's a truncated file.
I don't understand why that was done.?ÿ
If you wish to confirm your data a second run is critical.?ÿ
It's first principles, same as always.?ÿ
No one can say your data is good, I don't see anything wrong with it, it's a good start, now bring back a second set and you won't even need to ask.?ÿ
Is the bubble very necessary when fixing the points? I think there is a problem with the levelling bubble in my pole tripod rover