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Sub metric elevation surveying equipment for water systems in refugee camps

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Santiago
(@santiago)
FNG Member

Hello,

I am Santiago and I work as a water systems expert for the UNHCR, the UN refugee agency. I am not a surveyor myself.

I need advice on what kind of equipment to use to get elevations within a +- 0.5 meter error bracket to design water systems in remote locations worldwide (no RTK correction for example). Ideally, besides the precision, it would be:

  • Fast to operate and learn.
  • Lightweight.
  • Cross borders easily and quickly without sensibilities.
  • Affordable

 

Any information on technology or even particular equipment is greatly appreciated.

Thank you,

Santiago

This topic was modified 7 days ago by Santiago
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Topic starter Posted : August 1, 2022 2:29 am
Brad Ott liked
John Hamilton
(@john-hamilton)
1,000+ posts Member

https://positioningservices.trimble.com/services/rtx/fieldpoint-rtx/

I have used the Centerpoint RTX service with Trimble R10 receivers for water supply projects in Ecuador, but it is higher accuracy (and more $$$) than you require. 

 

https://www.waterworld.com/drinking-water/distribution/article/14276477/mapping-in-the-mountains

 

 

ReplyQuote
Posted : August 1, 2022 10:04 am
Brad Ott liked
Williwaw
(@williwaw)
1,000+ posts Member

You could use SBAS corrections, if they were available in the region your working in, which I don't believe includes Africa or the Middle East. I could be wrong.

https://en.wikipedia.org/wiki/GNSS_augmentation

Honestly? Nobody doing the work is a surveyor? Conventional level runs. Decidedly low tech, easy to learn, no whiz-bang flashy light electronics to raise suspicion. It's been done this way for a long time. 

The other option involves resource grade GPS and post processing and some body familiar with processing to apply the corrections. One unit collects GPS data as a base station and a second unit acts as a rover storing observation along the route. The roving data is combined with the base data to apply the necessary corrections to achieve desired accuracy. 

Good luck!

ReplyQuote
Posted : August 1, 2022 11:33 am

half bubble
(@half-bubble)
500+ posts Member

An X-90 OPUS static receiver and a used total station for trig levels based on the OPUS points.

 

ReplyQuote
Posted : August 1, 2022 1:04 pm
Bill93
(@bill93)
5,000+ posts Member

@half-bubble 

I doubt they care about actual elevation - only differences across the project, so trig levels would be sufficient.

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Posted : August 1, 2022 1:46 pm
FL/GA and half bubble liked
John Hamilton
(@john-hamilton)
1,000+ posts Member
Posted by: @half-bubble

An X-90 OPUS static receiver and a used total station for trig levels based on the OPUS points.

 

AUSPOS or Trimble RTX post processing would be the way to go rather than OPUS. 

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Posted : August 1, 2022 1:55 pm

John Hamilton
(@john-hamilton)
1,000+ posts Member

@bill93 That is true. We used ITRF2014 positions at the current epoch, and EGM08 geoid model.

The nice thing about using RTX is that the elevations are displayed right away, no comps necessary. I would assume that those decimeter solutions can be obtained using something less than a fully capable data collector, maybe even a cell phone, and be able to apply EGM08. But, I am not familiar with the non-survey grade Trimble receivers. 

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Posted : August 1, 2022 1:58 pm
Norman Oklahoma
(@norman-oklahoma)
5,000+ posts Member

Could be that something like the Lidar function on an Iphone 13 would answer the low cost / easily transportable portion of your needs. Not so sure about the easy to learn part, at least for the data resolution portion. Check out this Youtube on the process.

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Posted : August 1, 2022 5:04 pm
Santiago
(@santiago)
FNG Member

Honestly? Nobody doing the work is a surveyor? Conventional level runs. Decidedly low tech, easy to learn, no whiz-bang flashy light electronics to raise suspicion. It's been done this way for a long time. 

The other option involves resource grade GPS and post processing and some body familiar with processing to apply the corrections. One unit collects GPS data as a base station and a second unit acts as a rover storing observation along the route. The roving data is combined with the base data to apply the necessary corrections to achieve desired accuracy. 

Good luck!

@ Williwaw Sorry for the language barrier and the tech barrier.

What would be conventional level runs? These with an optical theodolite?

I am certainly hoping I am not the one doing these surveys :), but find a solution that can be rolled out. Refugee camps are usually in remote locations where contracting is complicated.

This post was modified 6 days ago by Santiago
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Topic starter Posted : August 2, 2022 3:02 am

Santiago
(@santiago)
FNG Member

@john-hamilton What would be the rough cost of equipment and subscription?

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Topic starter Posted : August 2, 2022 3:40 am
Santiago
(@santiago)
FNG Member

@bill93 Yes, we only need relative elevations but speed and ease of training would be nice to have.

Any particular equipment you could point to/recommend?

ReplyQuote
Topic starter Posted : August 2, 2022 3:45 am
Williwaw
(@williwaw)
1,000+ posts Member

@santiago 

ReplyQuote
Posted : August 2, 2022 9:03 am
Santiago liked

Norman Oklahoma
(@norman-oklahoma)
5,000+ posts Member

Topo surveying by stadia methods, which was discussed just last week in another thread, might be a low cost/low tech answer to your problem.    

ReplyQuote
Posted : August 2, 2022 9:22 am
Santiago liked
GeeOddMike
(@geeoddmike)
1,000+ posts Member

My understanding of your messages is that you want to determine heights of points in a water distribution system at refugee camps. If that is the case, you should be able to determine relative heights with a basic level, tripod and rod like this set:

BTW, the equipment shown above is illustrative of a low-cost option. I have not used them. 

I assume that you are talking about remote sites where equipment would be transported over bad roads and the like. This requires periodic checks to insure the level remains in adjustment.

Look on the web for “leveling peg test” or “Forster method” or “Kukkamaki method.” 

Setting or choosing stable and recoverable points at or near the sites of interest is important. 

I do not know how much you know about leveling. I recommend that all leveling begin and end on stable and recoverable points.

Establishing “permanent” monuments will expedite future expansion to new sites.

All leveling should be done in closed loops meaning that the summation of rod readings should equal zero with the difference being errors in your observations. Distances between the level instrument and rod should be consistent and with these distances limited by the ability of the instrument person to clearly read the rod. Intermediate sites observed between monumented points (turning points) should be use clear and distinct points (like a screwdriver driven into soil).

Note that my comments assume that you want to establish relative heights with respect a point on a relatively compact site and are not attempting to tie your work to a national datum

Make sure the tripod is firmly set and stable (check clamps and the tripod head and feet for any play. Keep the base of the rod (and face) clear of anything that would alter the rod’s direct contact with the point of interest. 

There are a number of samples of leveling notes on the web, I would look at examples from surveying programs at universities. Clearing labeling points and keeping track of them certainly helps.

With respect to GNSS, remember that physically meaningful heights like orthometric heights (H) are approximated by the combination of GPS-derived ellipsoid heights (h) and a geoid model (N). Their relationship is h - H - N = 0 (ideally). While both the UNAVCO and NGA sites have on-line tools reporting N they provide different numeric results. These sites require geographic coordinates for the point of interest.

The NGA tool is available from this link: https://earth-info.nga.mil/#tab_data

Good luck,

DMM

GNSS technology is the appropriate tool to connect distant sites together. Long leveling runs accumulate error and take a lot of time.   

 

 

 

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Posted : August 2, 2022 11:52 pm
Santiago
(@santiago)
FNG Member

Thank you everybody for the replies, it was very helpful 🙂 .

ReplyQuote
Topic starter Posted : August 3, 2022 12:10 am
Brad Ott liked

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