As noted earlier Field Dog will likely have error in his fixed coordinate pairs by using an RTN, where it would be best to use static network. Not as much error as running a open traverse with no fixed points at each end. The RTN will be better than nothing at all.
It's the old "condition equation vs. observation equation" conundrum. Being an open traverse there is no condition of a closed figure. Put it into least squares with proper weights (and nothing fixed) and see where it lands.
Field Dog, post: 439992, member: 9186 wrote: Looking for an example on how to calculate misclosure and adjustment of an open traverse. Can't find anything plain and simple on the Internet.
[USER=9186]@Field Dog[/USER]
Inverse your traverse point to the closing point. Take that distance and divide it by the total length of the route. That will give you a positional tolerance on your traverse. You can then being an adjustment via Compass, Crandall, Least Square, Transit or a host of other rules.
Assuming your traverse has 1-4 being the two beginning points (1&2) and the two ending points (3&4), then you "know" what the bearing is between 3 and 4 right? You can then look at the bearing you came up with when you closed into 3 and 4. The difference between those bearings will be your angular misclosure.
If you only have RTN points and no other traverse points shot along the route, then truly you are better to adjust (horizontally) the traverse with a compass rule. You will need to adjust the angles first. Simply prorating the angular misclosure through each of the traverse points will do that. For instance if you had 20 traverse angles turned on the ground, and you misclose with angles by 2 minutes. You would take 120 seconds and divide it by 20 and apply 6 seconds to each traverse point and then recompute your error. Then use the compass adjustment to adjust the remaining error out.
Don't believe the hype. If you don't have additional degrees of freedom (extra shots from GPS on your traverse points throughout the traverse), then this is the best method. If you do, then least squares will get you there.
Verticals can be adjusted in a myriad of methods to.
Williwaw, post: 439995, member: 7066 wrote: What projection are you working in FD. Is this a local system or standard projection, i.e. State Plane.
Working in NAD83 / Florida East (ftUS).
Brad Ott, post: 439998, member: 197 wrote: Did your traverse run generally in a north-south direction?
Yes.
Kris Morgan, post: 440104, member: 29 wrote: [USER=9186]@Field Dog[/USER]
If you don't have additional degrees of freedom (extra shots from GPS on your traverse points throughout the traverse), then this is the best method. If you do, then least squares will get you there.
We shot point # 4 (Orange County benchmark) and point # 13 with GPS. Are there any free least squares adjustment programs I can play with?
Kris Morgan, post: 440104, member: 29 wrote: [USER=9186]@Field Dog[/USER]
Verticals can be adjusted in a myriad of methods to.
We're going to level through all the traverse points.
Thanks for the simple and concise explanation!
With your GPS control of low quality least squares is the best solution for this. You can put some large error estimates on those GPS points so your total station work doesn't get distorted. You could try WinnCMM to adjust horizontally. It's based on an old DOS least squares adjustment program Ray Hintz from University of Maine developed. It's a little clunky but it works great, and it's free.
Is the demo of Star*Net still available free with 10 point limitation ?
Field Dog, post: 440237, member: 9186 wrote: Are there any free least squares adjustment programs I can play with?
Bill93, post: 440249, member: 87 wrote: Is the demo of Star*Net still available free with 10 point limitation ?
It is. And if you have Carlson Survey you already have SurvNet.
Field Dog, post: 440230, member: 9186 wrote: Yes.
Then I think you might have a simple rotation to make. Maybe.
Brad Ott, post: 440259, member: 197 wrote: Then I think you might have a simple rotation to make. Maybe.
Inverse the start and end points of the traverse. How close does it match the inverse distance of the comparable points tied by GPS? They match closely it's a simple rotation. In order for least squares to be an appropriate tool you'd need redundant measurements, but it could help flag a blunder somewhere, systematic or random but trying to massage out blunders isn't the appropriate approach. If you divided the two overall measured distances, does the result match closely with the scale factor for your SP system? The DC could be storing a ground and not grid distance. That can account for a half foot over the length of a long traverse. Good luck and kudos for trying to better understand.
Just because I'm paranoid, doesn't mean they aren't out to get me.
Kris Morgan, post: 440104, member: 29 wrote: [USER=9186]@Field Dog[/USER]
Inverse your traverse point to the closing point. Take that distance and divide it by the total length of the route. That will give you a positional tolerance on your traverse.
0.73 / 6519.09 = 0.00261197882
1:383
Something is definitely wrong!
Field Dog, post: 442604, member: 9186 wrote: 0.73 / 6519.09 = 0.00261197882
1:383
Something is definitely wrong!
Sorry, I had them backwards. 6519.09/0.73 = 1:8930. Not great but not bad, especially if you have a large scale factor to contend with.
What was the angular error???
Kris Morgan, post: 440104, member: 29 wrote: [USER=9186]@Field Dog[/USER]
Assuming your traverse has 1-4 being the two beginning points (1&2) and the two ending points (3&4), then you "know" what the bearing is between 3 and 4 right? You can then look at the bearing you came up with when you closed into 3 and 4. The difference between those bearings will be your angular misclosure.
The angular misclosure is 0?ø00'33".
Field Dog, post: 442609, member: 9186 wrote: The angular misclosure is 0?ø00'33".
How many traverse stations?
Field Dog, post: 442609, member: 9186 wrote: The angular misclosure is 0?ø00'33".
Over 6500 feet, this smells like a rotation issue, maybe resulting in only 0.3'~ish error of closure?
If he's checking the angular misclosure against GNSS station pairs on each end, each pair is probably lot closer together than 6500 ft so the corresponding distance error would be much smaller..
Explain that aledged 33" error.
You have 4 GPS points all with a positional tolerance. In small words that means your can hold nothing fixed. Properly comparing your traverse and post processing, I say your error would be much less.
Paul in PA
Paul in PA, post: 442638, member: 236 wrote: You have 4 GPS points all with a positional tolerance. In small words that means your can hold nothing fixed.
This business of mixing GPS points and traverse data by compass rule adjustment (or worse by translating / rotating in CAD) is just not the best way to get it done. Frankly, I'd go so far as to say it's just not very professional. LS is clearly the way to go.