Results 1 to 10 of 10

Thread: Rtk

  1. #1
    Member
    Join Date
    Feb 2010
    Posts
    269
    Thanks
    41
    Thanked 67 Times in 44 Posts
    Rep Power
    189
    Reputation
    480

    Default Rtk

    This kind of falls into two areas..going to soap box here..and ask how many of you have had problems with RTK bases causing interference? I have noted of late in my local area, there are many "aust wide" licenses causing problems. Yes Im aware of conditions under ACMA, just wondering how others are going...just seems that people are using them at a whim, without thinking about problems.

    One example, a portable base was set up (looking at the stream mulitpathing) and causing no end of agro. And whats your thought on CORS vs conventional base.

    Cheers
    Last edited by donk; 26-02-10 at 08:36 PM. Reason: Typo



Look Here ->
  • #2
    Senior Member
    Downunder35m's Avatar
    Join Date
    May 2009
    Posts
    4,063
    Thanks
    101
    Thanked 1,796 Times in 862 Posts
    Rep Power
    630
    Reputation
    15704

    Default

    I have no idea what you are talking about....
    Last edited by Downunder35m; 26-02-10 at 10:02 PM.
    Tomtom GO730 ,Navcore 9.004 ,Bootloader 5.5256 ,Map :Australia 845.2661
    ttmaps and Tomplayer on 16GB SDHC class6
    Password for all my files: downunder

  • The Following User Says Thank You to Downunder35m For This Useful Post:

    BlackDuck (27-02-10)

  • #3
    Member
    Join Date
    Feb 2010
    Posts
    269
    Thanks
    41
    Thanked 67 Times in 44 Posts
    Rep Power
    189
    Reputation
    480

    Default

    ahh its just GPS stuff

  • #4
    Junior Member
    Join Date
    Feb 2010
    Location
    Brisbane
    Posts
    14
    Thanks
    4
    Thanked 0 Times in 0 Posts
    Rep Power
    0
    Reputation
    10

    Default

    These things are common in the bush and one use is broad acre farming. As to interference sounds very odd to me.

    Google Real Time Kinematics if you're bored. Actually on second thoughts...

  • #5
    Senior Member
    Join Date
    Aug 2009
    Location
    Sydney
    Age
    43
    Posts
    1,217
    Thanks
    189
    Thanked 615 Times in 150 Posts
    Rep Power
    0
    Reputation
    2828

    Default

    are you guys talking about whats going to happen in the furture ?
    Donk, did you come back to 2010 from 2050 ? if so, please tell me how you did this ?

  • #6
    Member
    Join Date
    Feb 2010
    Posts
    269
    Thanks
    41
    Thanked 67 Times in 44 Posts
    Rep Power
    189
    Reputation
    480

    Default

    LOL...RTK has been used in farm appliactions for many many years. Willyroo....is right there, to a degree. Its high accuracy GPS stuff, but not just for farm applications, survey, military etc etc

    There are two issues I guess with portable bases, the one I mention had multipathing in the correction signal (but this wasnt the issue at hand)

    IE a device RX L1 & L2 and a base, with a fixed location, transmitting L1 on a different frequency.

    There are a number of bases around australia..infact thousands of them...they use a range of systems..900Mhz and 450 Mhz are popular. Now many have Australia wide licenses, but general farmers, mine guys and others have no way of checking if they are indeed causing problems to other services, be it LMR, other GPS users etc.

    Its more the 450Mhz stuff that im interested in rather than 900Mhz.

    Multipathing - is simply a reflected signal causing problems with timing calculations (yes I know there is more, not going into fine detail here) this obviously causes location problems.

    CORS - Vig gov has a network, and other states are looking at the same. Its used by farmers, government agencies, survey companies etc etc for many many uses.

    This stuff has been around for a long time (in terms of technology)

  • #7
    Senior Member
    Downunder35m's Avatar
    Join Date
    May 2009
    Posts
    4,063
    Thanks
    101
    Thanked 1,796 Times in 862 Posts
    Rep Power
    630
    Reputation
    15704

    Default

    So I had a quick look on some of the systems out there...
    Still not 100% sure why I would need something like that , but I'm sure ppl who use it will know why the have it

    If I see it right the concern here is the transmitting of signals from hand held devices to the base.
    Both the 400 (and450) and the 900Mhz bands are highly regulated and only certiain frequenzies are free to use - and with limited signal strenghts.
    The signal itself would only be a problem if some other device is transmitting at the same frequency and with a signal strengh that is too weak and would be overpowered by the RTK system.
    One possible problem I could see are the harmonic waves that can occur more or less intense.
    The signal strengh is limited on these devices and therefore after a few 100meters out of the transmitting range there should be no interference at all.
    I'm not 100% sure about the Australian laws and regulations ,but in Europe an electronic device must not cause any interference and more important : it must be protected against interference from outher sources.
    Since my TV and DVB-T receiver both don't like it when I switch the lights off I would say Australia does not care about that sort of protection....
    Tomtom GO730 ,Navcore 9.004 ,Bootloader 5.5256 ,Map :Australia 845.2661
    ttmaps and Tomplayer on 16GB SDHC class6
    Password for all my files: downunder

  • #8
    Member
    Join Date
    Feb 2010
    Posts
    269
    Thanks
    41
    Thanked 67 Times in 44 Posts
    Rep Power
    189
    Reputation
    480

    Default

    Thanks Downunder, but harmonics are not so much the issue.

    umm try an explain a bit better here, the base transmits GPS data, ie that is a fixed point GPS rx, the data is then broadcast via a number of methods.

    There are normally portable bases and fixed. The output of the transmitter will obviously depend on power source and type. An example of the radio may include Pacific Crest, Tait, Freewave and the list goes on. In this particular area the common base output is around 25 - 30watts 450 Mhz. (in case of 900Mhz around 1 watt) portable around 1-10watts

    Now thats excluding repeater networks. There are a couple of points, increasing distance from a base, reduces overall accuracy...in general terms prehaps 10 - 15Km max from the base (not true in all cases)...howeve correction signal may be broadcast further. EG I can see packets from a 900Mhz base some 60 - 70Km away, but this would not be usable at that distance to be "accurate"

    So in these cases, in simple terms the rover / vehicle rx GPS and the fixed base tx correction info to the rover.

    Thats all well and good, now there are a few companies that hold Australia wide licenses. Many of those licenses have conditions attached. In the past 6 - 12 months I have noticed a slight increase in equipment loosing accuracy, and starting to find that GPS bases some distance away are causing problems, ie the rover is grabbing a packet of data being broadcast from another site. That packet will contain data from a different location, and screw thing up a bit.

    Whilst its regulated, many people are just shoving gear in without thinking of the implications (harmonics), and wondering if anybody else has seen the same thing, and if so, has CORS reduced this (if you have CORS)

    Yes, regulated...in theory....Now many of you may thing that wide open space, no congestion....but propergation of late (here anyway) has me seeing data streams upto 400Km away...yes the band has opended up a bit.

    To give an idea, I can think of some 20 - 30 plus bases within 50 - 60 Km of my locations (excluding 900Mhz stuff)...then throw into the mix the fact the band is working quite well, is proving a little interesting. I should also point out that CMR is often full duplex, and crammed into small areas eg 450 - 451, 465 - 466, some in 460 to 465 Mhz range.

    To be fair, some problems are just natural evens or by human. In anycase, lots of people who use this gear just do not have the facilities to know if they are causing / experiancing a problem

    As mentioned broadacre is common use of this equipment, and its also common on earth moving gear, survey..so it can be mixed and in a wide range of occupations and locations.

    Im wondering if anybody else has seen this ????
    Last edited by donk; 27-02-10 at 02:20 PM. Reason: last line question

  • #9
    Member
    Join Date
    Feb 2010
    Posts
    269
    Thanks
    41
    Thanked 67 Times in 44 Posts
    Rep Power
    189
    Reputation
    480

    Default

    Those that are interested in this kind of GPS Technology






  • #10
    Senior Member
    Downunder35m's Avatar
    Join Date
    May 2009
    Posts
    4,063
    Thanks
    101
    Thanked 1,796 Times in 862 Posts
    Rep Power
    630
    Reputation
    15704

    Default

    Interesting!
    At least now I know why having moderator and more sub-section here would be a good idea
    There is not much info to find on user friendly websites and it seems these systems are widely used over Austrlia.
    And it confirms my previous statement the possible interfence should not be an issue - as long as there no amateur radio stations with hig power amplifiers are aorund sending in the same frequencie band or on one of the harmonic frequencies used.
    Tomtom GO730 ,Navcore 9.004 ,Bootloader 5.5256 ,Map :Australia 845.2661
    ttmaps and Tomplayer on 16GB SDHC class6
    Password for all my files: downunder

  • Bookmarks

    Posting Permissions

    • You may not post new threads
    • You may not post replies
    • You may not post attachments
    • You may not edit your posts
    •