Comments and explanations please, on why it is better to measure the short lines. I guess I am specifically asking about "station pairs". Why is it better? Are the results better? Or is just good procedure?
Just wanting to understand this.
Stumbling in the dark.........Tom Bryant PLS-BE St Louis MO
Many of the 'short lines' in a large project fall into the context of what in a conventional survey would be termed 'cut-off' lines..Basically a direct observation from station to station...
While I doubt that it makes much positional accuracy difference in a good tight GPS network, it does add redundancy and gives you an estimated error on that line "directly" as opposed to a calculated estimation...(the difference between an 'inverse' and a 'shot distance')
I always measure the short lines since it tightens the point to point solution and localizes any error to the small triangle solution, which is most important to my end users (other surveyors)...
Simple answer, it's both good procedure and produces better 'on the ground' results...
Having a direct observation also aids in troubleshooting orthometric heights...I can run a level line between two relative close spaced marks to add/check the differential and compare to the geoidal modeling..
TM-Not equipment specific
Tom
I always observe the "short" lines because this is usually the line I use for total station work and I have a direct comparison with the EDM distance.
As to "why" is it better.... I'll leave that to the more informed... I just feel better doing it..
Steve G
It's important to utilize the direct connection in your network adjustment. Assuming your work is performed correctly, it could be easy to achieve a positional accuracy of 1-2 cm (horizontal) for any given point. Therefore, for example, if you have 2 unconnected points 400 meters apart they could each of a positional uncertainty relative to the baseline of let's say 1.5 cm. That means that between them you could have 3 cm and 400 m divided by 3 cm is 1:13,333 - You could do better with conventional measurments. By including that line in your adjustment, properly weighted of course, you can reduce the relative positional distortion between these 2 points. There is an old rule of thumb from triangulation that still seems have be a good rule with GPS.