Should I rotate my traverse?

fobos8 · 2021-08-06T06:20:00Z

Hi guys A local surveyor carried out a topographical survey on a plot of land 12 years ago. The project was to demolish the old farming buildings that were there and build some houses. The survey was carried out to a local grid and level datum. The development didn't get off the ground at the time, but last week a project manager asked me to get involved as they're building on it soon. The size of the plot of land is 190metres by 70 metres. I attended the site yesterday, found 4 of the original survey stations, performed a closed-loop traverse, and added in some extra stations. I also surveyed a few corners of neighbouring houses, and other boundary features on the original survey to ensure there is a good correlation between my survey and the original one. The stations I found were in tarmac/ashfalt. The only two stations I could find to set up from were too close for me (28 metres) for a large site, but it was all I had so I got on with it. So the first back sight was 28 metres, the deltas were 0mm horizontal and 5mm for vertical. I traversed round adding in my extra stations and finding and traversing the other 2 original stations which were both around 190 metres away from my original short baseline. The traverse accuracy was great, 1 in 190,000. However, the co-ordinates I got for the 2 stations far away from my original baseline weren't amazing. I got them about 20mm away in x,y from the survey carried out 12 years ago. The levels were in good agreement, within 5mm. My feeling is that I suffered from my short starting baseline. If I rotate the whole traverse around my first set on station I can get x,y agreement for all stations to those in the original survey of 6mm. Is there any advantage to doing this? I don't have and don't fancy getting least squares software for this one project. Kind regards, Andrew ?ÿ ?ÿ

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Strictly Surveying

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nate-the-surveyor

(@nate-the-surveyor)

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Just fyi, here is a handy tip. Analyze the existing coordinates. (Discover it runs 1-300).

So, start your job out at 401. So that you have your OWN values, and coordinate names for those same points on the ground.?ÿ

Now, you can freely rotate/translate/scale your data, without entanglement with his points, and data.

Thank you,

Nate

Posted : August 7, 2021 11:43 am

fobos8

(@fobos8)

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@nate-the-surveyor?ÿ

Thanks Nate, so what you're saying is... have my own station names and co-ordinates even though they are a few mm different from the original stations?

Posted : August 8, 2021 3:39 am

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Should I rotate my traverse?

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