Hi everyone,
I’m just after some facts before I jump into purchasing a pair of RS+ units.
In Australia (NSW & QLD) if I’m wanting to get lat, long & elevation with cm accuracy while carrying out terrain profile data collection on sections of existing power lines i.e. centerline ground profile (2 span to 100 spans) & existing power pole location & other ground points (e.g. ground stays, T-Offs, roads, fences, dams etc) to be used to do modeling for load studies to identify where possible ground clearances issues may arise as loads increase & lines sag, requiring rectification options.
So with the above information in mind what do I need apart from two reach rs+ units, tripod for base rs+, telescopic survey pole for the rover rs+, the ReachView app on a mobile device? Do I need any GNSS subscriptions or can I just set up as instructions & videos show and get cm accuracy on X, Y & Z anywhere that I have a reasonably clear view of the sky & where the two rs+ units can communicate & the rover can receive it’s connections from the base, without paying anything (gps subscriptions etc) apart from the cost of the 2 reach rs+ units a tripod and survey pole?
Hope you can help.
Cheers B
It depends on whether or not you have known positions available, and if you need relative or absolute precision/accuracy.
Christian Grüner thanks for responding,
What relative precision/accuracy will I get if I have known positions?
What absolute precision/accuracy will I get if I have if I have known positions?
And
What relative precision/accuracy will I get if I DON’T have known positions?
What absolute precision/accuracy will I get if I DON’T have known positions?
And what additions (item, time, effort & or cost) would it take for best accuracy (absolute) in the worse situation (no known positions for base)? because depending on the additional effort, items, time & cost to gain absolute accuracy it may be that relative position accuracy is good enough for the exercise.
Thanks again
Cheers B
It all depends on your baseline, and if you have time to post-process.
If you don’t have any known positions within 10 km, you will have to postprocess your base-position to get an absolute position of your base (using i.e. CORS stations).
the relative accuracy/precision will be the same regardless of known base-position (but deteriorates with longer baselines)
Hmmm, sounds like to much complexity and at site & in office time for the type of work I want to do (1 to 10 cm accuracy would do); probably quicker to maintain status quo & do point to point to point with quality (distance, inclination & bearing) rangefinder and offsider az I do now. I hoped it may be as simple as setting up a base then moving along the powerline with the rover taking marks (a minimum of 3 for flat country & every elevation change for undulating sections), adding notes to reachview and ending up with a file (csv or other) for use later, then retrieving the base & moving the the next location & repeat.
Thanks again
If you place your base with an NTRIP services, then the above would be possible.
The RS+ survey kit will work fine for your needs and there is nothing wrong with the standard traversing of the base. After the first base position you want to manually enter in the coordinates from your last rover position, but for maximum accuracy I would plan the mission and select your base points ahead of time. You can then use the two units to collect & post-process those base positions ahead of time. Then all you have to do is manually enter those coordinates into Reachview.
If you are travelling long enough distances to warrant it, I would suggest the parts listed in the linked post below to make a car mount. It’s a quick release from the rover pole to the magnetic mount for your vehicle.
Hi Michael Lambert, thank you for you input, so it is possible and relatively straightforward; I just need to find and study up on the processes required. I’m keen to learn and adopt the required knowledge, understanding and equipment if the ROI is reasonable; everything I’ve seen & heard so far sounds great but I only have access to surveyors who all poo-poo the reach rs concept and I dont know any drown dudes who could maybe help and put everything into layman’s terms.
Can you suggest anywhere that I can get the required knowledge provided in layman’s terms please?
Thanks heaps again
Regards B
if you are working within a reasonable distance (i don’t know what that is) of an ARGN station then you may be able to get near a few cm absolute accuracy by post processing for your base position.
ftp://ftp.ga.gov.au/geodesy-outgoing/gnss/pub/maps/argn_map.pdf
otherwise without a subscription to a network correction service (~AU$3,000 p/a) you will have to make do with absolute positioning of the base of a few m, then good relative (cm) accuracy between base and rover.
you may be able to obtain coordinates from nearby survey marks in NSW if you get access to the SCIMS survey mark database. which will save you having to subscribe to a network correction service, or post process from an ARGN station. the surveyors you have access to should be able to help you with this.
i’m a surveyor and i don’t quite poo-poo the reach RS concept, but my one and only single-frequency RTK experience was enough to put me off it for a long time. i hope the ambiguity resolution algorithms have sped up since javad/topcon days in 2001. i’d be sure they have, but i don’t ever have to find out.
possible and relatively straightforward to get answers, yes. Hard to know if your answers are right.
Almost 20 years, I’m sure you can’t compare 
As long as you know the limitations of single frequency GNSS, it’s a fantastic product!
i’m sure they have sped up. if they hadn’t, these forums would be full of book recommendations to read while you wait for first lock!
If I’m supplied longitude and latitude for all existing poles (checking if ground level elevation is available too but expect its not) can the pole be used as known locations to a certain extent and utilized for corrections in some way.
Lat & Long within 20cm is tolerable but its the elevation for ground level/terrain profileing I’d like to be within 10cm or better.
Can you establish the base over these known coordinates without too much sky blocking?
The heights you need, are they relative or absolute?
If relative, you could just traverse the rover and base (to have a short baseline)
Hi & thanks again Chrustian,
As you can tell I have almost no experience with survey but If by " Can you establish the base over these known coordinates without too much sky blocking?" you mean can I overlay the provided poles lat’s & long’s on to a GIS or something like Google Earth then yes I can easily do that on a PC.
And " The heights you need, are they relative or absolute? relative, you could just traverse the rover and base (to have a short baseline)" do you mean “relative” as in comparison to a starting point ie aquire the ground level elevation of the first of a series of poles and every subsequent elevation measuremnt in the series would be in relation to that first measurement then yes that would be all in need as long as those elevations are accurate.
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