[talk-au] Increased precision options for Australia - QZSS, SBAS or Galileo

Grant Slater openstreetmap at firefishy.com
Tue Jun 12 10:34:19 UTC 2018


Hi All,

I have 2 of these for RTK GNSS receivers: https://emlid.com/reachrs/

1 ReachRS unit becomes the RTK static "base" and you needs a very
accurate position measurement and good signal. To get the most
accurate measurement I use my base and connect it to another base
using an NTRIP network. I'm in the United Kingdom and I connect to the
free NTRIP network available here: http://www.euref-ip.net/home . I've
also used the South African free NTRIP network trignet.co.za
Geoscience Australia seem to offer a NTRIP network here:
https://www.auscors.ga.gov.au/
Note that max workable distance between base and rover is only around
20km. I've got it to work at 80km, but needs exceptionally clear area
(unobstructed sky) and a lot of patience to get the position fix.

Once I have my static ReachRS measured, I then connect it up to the
2nd ReachRS as a roving unit via built-in radio or Cellphone. A
reasonable maximum distance between Base and Rover is around 20km.

The rover is good for measuring points, but starts to struggle if
moved above walking pace or has an obstructed sky (read: trees etc)
Repeatable accuracy is <10cm horizontal and similar vertical.

It is possible to do the above with a single unit if you can rely on
an existing NTRIP network, but I believe you then cannot then use the
GLONASS network for getting a fix due to different antenna types
between base and rover.

The ReachRS is a single frequency receiver and needs better signal and
is slower to sync than a dual frequency receiver. In the next year or
2 there are likely to be more dual frequency receivers from the likes
of u-blox. The swiftnav.com unit looks interesting.

The ReachRS receiver uses a u-blox Neo-M8T chip and the rtklib
software. A homebrew alternative would be to use
http://www.csgshop.com/product.php?id_product=257 and rtklib yourself.
See: https://www.blackdotgnss.com/2017/03/25/u-blox-neo-m8t-part-i/

Interest? Highly recommend blog: https://rtklibexplorer.wordpress.com/

Kind regards,

Grant


On 12 June 2018 at 10:58, Leith Bade <leith at bade.nz> wrote:
> If you want to do RTK you can do it for less then $1000 now. The company I
> work for makes one of these lower cost options https://www.swiftnav.com. RTK
> enabled centimetre level positioning with a good $600 antenna.
>
> If you want to use the SBAS trial you need a receiver that allows you to
> select the SBAS satellite PRN ID of 122 and will allow a good receiver to
> get about ~1.5m accuracy. For example the Ublox receivers will work, as will
> most standalone GPS receivers
>
> Galileo is still under development, will offer similar performance to GPS.
> It will be another 2 years before this system is complete with all 24
> satellites.
>
>  Android devices are hard-coded by the manufacturer as far as the GPS
> settings so you would need to wait for an Android update that knows about
> the Australian satellite and QZSS (which might take several years to be
> common place).
>
> My recommendation is to look at standalone GPS receiver like a Ublox M8
> based device, that uses an external magnetic antenna you put on your car's
> roof.
>
>
> Thanks,
> Leith Bade
> leith at bade.nz
>
> On 12 June 2018 at 12:39, Alex Sims <alex at softgrow.com> wrote:
>>
>> Hi,
>>
>>
>>
>> I’m really wanting to have better accuracy from GPS for use with
>> Openstreetmap. I can use survey marks and a laser rangefinder, but having a
>> portable GPS would make so much easier to fix errors where objects have been
>> armchair mapped or even GPS mapped with errors up to 3 meters.
>>
>>
>>
>> I have tried three approaches
>>
>> QZSS – I can see this on my Android mobile phone but it doesn’t seem to be
>> used. It seems as though I need a Japanese market device and even then I’m
>> not sure I’ll get an increase
>> Galileo – looks promising but when I’ve tested on supported devices
>> (friends who have recent phones) the accuracy isn’t delivered. Further
>> investigation shows that there aren’t enough satellites in service yet most
>> of the day to give 4 visible. (Using GNSS View http://qzss.go.jp/en/ English
>> text)
>> Lastly the SBAS trial from Geoscience Australia -
>> http://www.ga.gov.au/scientific-topics/positioning-navigation/positioning-for-the-future/satellite-based-augmentation-system
>> - nothing magical has happened with any of the consumer grade devices I have
>> access to. Also not sure how to test on an Android device if it is being
>> used.
>>
>>
>>
>> Has anyone obtained sub-meter accuracy from any of these approaches, it
>> must be possible?
>>
>>
>>
>> Please discuss.
>>
>>
>>
>> Alex
>>
>>
>> _______________________________________________
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>> Talk-au at openstreetmap.org
>> https://lists.openstreetmap.org/listinfo/talk-au
>>
>
>
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