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Real Time Network Fundamentals Shane “Trap” Traffanstedt Earl Dudley, Inc.

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Presentation on theme: "Real Time Network Fundamentals Shane “Trap” Traffanstedt Earl Dudley, Inc."— Presentation transcript:

1 Real Time Network Fundamentals Shane “Trap” Traffanstedt Earl Dudley, Inc

2 GPS before the internet. Static RTK CORS - Static Evolution

3 It is more than just a series of GNSS Reference Stations connected to a central server via the internet. What is a Reference Station “Network”?

4 It is more than just a series of GNSS Reference Stations connected to a central server via the internet. Each of the stations is linked to the ones around it,. What is a Reference Station “Network”?

5 It is more than just a series of GNSS Reference Stations connected to a central server via the internet. Each of the stations is linked to the ones around it, and those to the ones around them, creating a network of data. What is a Reference Station “Network”?

6 It is more than just a series of GNSS Reference Stations connected to a central server via the internet. Each of the stations is linked to the ones around it, and those to the ones around them, creating a network of data. From this network, the rover can get information related to all the surrounding stations and not just one single station. (think of it like a continuous resection) What is a Reference Station “Network”?

7 NAVSTAR (American Satellite System) Navigation Signal Timing and Ranging GLONASS (Russian Satellite System) Global Navigation Satellite System GNSS Global Navigation Satellite System The new term for ALL the constellations. Europe – GALILEO China – COMPASS What Satellite constellations' are used, and how ?

8 24hr/day view of the sky with no obstructions above 5º cut off angle. 5 ° What Satellite constellations' are used, and how ?

9 24hr/day view of the sky with no obstructions above 5º cut off angle. Good geometrical position (think of it like PDOP) BAD GOOD What Satellite constellations' are used, and how ?

10 One limitation to a good Network is the distance between the reference stations. In order to create a good network the maximum distance between reference stations varies between manufactures, but is around 70K (43.5 miles). BAD GOOD <70K =70K <70K =70K >70K What Satellite constellations' are used, and how ?

11 A reference network does not work off of any State Plane Coordinate system. Instead they work on a common system known as Cartesian Coordinates, and in meters. This allows for one single datum and from there you can easily convert your coordinates, or units, to whatever best fits your project. X j l h P Z Y  Origin coincides with Earth’s center of mass  X and Y axes are perpendicular to each other in the equatorial plane  Z axis is at right angle to the X,Y plane and coincides with the Earth’s rotational axis Satellite Datum

12 Once the network administrator has worked out a good location and a site has been reviewed for having a great view of the sky, as well as high speed internet, then a real time data feed goes directly into the central server. So how does this all tie together?

13 Now that a good position has been determined we have to decide how to get this information out to the rover units. The most common format is RTCM. The current version of RTCM is v3.1, although some older units still have to use v2.2 and v2.3. Therefore all of these need to be available in order for everyone to continue with the equipment they currently have, and not be forced into upgrading their units. Radio Technical Commission for Maritime Services Some equipment can not use GLONASS so this also must be taken into account. So how does this all tie together?

14 TCP/IP A single connection with a single output option. TCP = Transmission Control Protocol Think of this like it was a phone number, for example to Earl Dudley. IP = Internet Protocol Think of this like it was an extension, for example to Trap’s desk at Earl Dudley. NTRIP A single connection with multiple output options more commonly referred to as a Mount Point. Networked Transport of RTCM via Internet Protocol Some older equipment can not use NTRIP and therefore can only connect via TCP/IP. So how does this all tie together?

15 NTRIP will give you the format of the data, and with most models, actually set the unit to match the incoming date stream. TCP/IP you have to know the data format and set it yourself. NTRIP Mount Point list is pulled from the server and can be updated very easy. TCP/IP you have to download a paper copy and know that something has changed. NTRIP will tell you that GLONASS in included in the data stream. TCP/IP you have to know. NTRIP, due to the small screens on data collectors, has a limited amount of space to describe the Mount Point. TCP/IP you are only limited to the amount of paper you want to print. NTRIP vs. TCP/IP?

16 The administrator of the network decides what products they want to include in their NTRIP Mount PT list and gives each of them a name. For example I named our product for connecting you to the closest reference station with RTCM v3 using GLONASS to be RTK_3. The same product without using GLONASS is named RTK_3noGG. From most web browsers, you can type in the IP and Port for the NTRIP Server and see the Mount Point List on your PC. For example try typing in :21000 in the address bar of your browser. You should see something like the following: Now what happens?

17 SOURCETABLE 200 OK Server: TopNET-V 9.0/1.0 Content-Type: text/plain Content-Length: 1623 STR;RTK_2.3noGG;RTK_2.3noGG;RTCM 2.3 RTK;3(10),22(10),23(10),24(10),18(1),19(1);2;GPS;iNET South; USA;32.83;273.17;1;0; TopNET-V;none;B;Y;; STR;RTK_2.3;RTK_2.3;RTCM 2.3 RTK;3(10),22(10),23(10),24(10),18(1),19(1);2;GPS+GLONASS;iNET South; USA;32.83;273.17;1;0; TopNET-V;none;B;Y;; STR;NET_3;Network RTCM 3 w/GG;RTCM 3.0;1004(1),1012(1),1005(10),1007(10),1033(10);2;GPS+GLONASS;iNET South; USA; 32.83;273.17;1;1;TopNET-V;none;B;Y;; STR;NET_3noGG;Network RTCM 3 noGG;RTCM 3.0;1004(1),1005(10),1007(10),1033(10);2;GPS;iNET South;USA;32.83;273.17;1;1;TopNET-V;none;B;Y;; STR;RTK_3;RTK_3;RTCM 3.0;1004(1),1012(1),1005(10),1007(10),1033(10);2;GPS+GLONASS;iNET South;USA;32.83;273.17;1;0;TopNET-V;none;B;Y;; STR;RTK_3noGG;RTK_3noGG;RTCM 3.0;1003(1),1005(10),1007(10),1033(10);2;GPS;iNET South;USA;32.83;273.17;1;0;TopNET-V;none;B;Y;; STR;NET_2.3noGG;Network RTCM 2.3 noGG;RTCM 2.3 RTK;3(10),22(10),23(10),24(10),18(1),19(1);2;GPS;iNET South; USA; 32.83;273.17;1;1;TopNET-V;none;B;Y;; STR;NET_CMR;NET_CMR noGG;CMR;1(10),0(1);2;GPS;iNET South;USA;32.83;273.17;1;1;TopNET-V;none;B;Y;; STR;RTK_CMR;RTK_CMR noGG;CMR;1(10),0(1);2;GPS;iNET South;USA;32.83;273.17;1;0;TopNET-V;none;B;Y;; STR;EDBM3;EDBM3;RTCM 3.0;1004(1),1012(1),1005(10),1007(10),1033(10);2;GPS+GLONASS;iNET South;USA;30.39;270.94;0;0;TopNET-V;none;B;Y;; STR;NET_2.3;Network RTCM 2.3 w/GG;RTCM 2.3 RTK;3(10),22(10),23(10),24(10),18(1),19(1);2;GPS+GLONASS;iNET South; USA; 32.83;273.17;1;1;TopNET-V;none;B;Y;; STR;DGPS;TopNet;RTCM 2.3 DGPS;3(10),1(1),31(1);0;GPS+GLONASS;iNET South;USA;32.83;273.17;1;0;TopNET- V;none;B;Y;; ENDSOURCETABLE Now what happens?

18 Below is an example of this as seen in TopSurv on a FC-2500 data collector. Now what happens?

19 The rover user selects the product he/she wants to use that best fits their equipment and project needs. For example, if my receiver does not have the ability to use GLONASS, then I would only use the products that do not include the GLONASS in their data stream. We are also working in an area where we do not have good geometry between the reference stations. Therefore the best product for us would be RTK_3noGG. Now what happens?

20 The rover user selects the product he/she wants to use that best fits their equipment and project needs. For example, if my receiver does not have the ability to use GLONASS, then I would only use the products that do not include the GLONASS in their data stream. We are also working in an area where we do not have good geometry between the reference stations. Therefore the best product for us would be RTK_3noGG. This will connect you to the closest reference station to you and work similar to how your typical base/rover units work. Now what happens?

21 However, if you were to have equipment that does have the ability to use GLONASS, and you were in an area where you were surrounded by reference stations that had good geometry, then you would want to use NET_3. Now what happens?

22 However, if you were to have equipment that does have the ability to use GLONASS, and you were in an area where you were surrounded by reference stations that had good geometry, then you would want to use NET_3. This product will set a calculated local reference point that is 5K (3.1miles) from your navigated position, in line with the nearest real station. Now what happens?

23 This local point is calculated from a model of all the stations in the network, and then passed on to the rover. Now what happens?

24 Below is basically how the procedure should go. 1.Power on your equipment, the unit will read your configuration file to see what devices to use and how to use them. 2.If a device is not already powered on (GR-3, Airlink), then the configuration will power it on (GFU24, GFU19). 3.These next two steps can happen in any order, but both need to happen before moving on to the next step. the receiver needs to start tracking satellites and get a navigated position (Autonomous position). the modem must be connected to the internet. Let’s get started.

25 Below is basically how the procedure should go. 4.We now need to connect to a network server, IE iNET, ALDOT, TDOT. Your c urrent position is sent to the server and based on the TCP/IP or NTRIP Mount Point you selected it tries to connect you to that product. Depending on the product you selected it either connects you up to the nearest reference station, or it creates a local station for a network solution. 5.Once your position is in the server, the product is selected, and your username and password are verified, then the server starts sending the data feed to the rover. Let’s get started.

26 Definition of ACCURACY 1 : freedom from mistake or error : correctness 2a : conformity to truth or to a standard or model : exactness Definition of PRECISION 1 : the quality or state of being precise : exactness 2a : the degree of refinement with which an operation is performed or a measurement stated So we ask ourselves, “is GPS accurate, precise, or both?” Source = Accuracy vs. Precision

27 So which one best describes GPS? Accuracy vs. Precision

28 Actually it can be both. First and foremost it is precise, or as some refer to it “repeatable”. What we mean by this is that if you make a measurement, cut the unit off and back on, and then reshoot the same point, the positional differences will be minimal. This holds true for base/rover setups, as well as network solutions (single base line or network). Then, with proper field procedures, we the user can make it more accurate. Accuracy vs. Precision

29 The first question we have to ask ourselves is what accuracy are we looking for? o Meter - With a single epoch we can use pretty much any product at an extremely long range ( miles) and should be able to achieve better than 1m for horizontal, 2m vertical. With enough satellites this is possible even in moderate woods. GLONASS helps here a whole lot.  Good for wetlands delineation, preliminary planning, and rough stakeout. o Foot - With a couple epochs (3-5) in the wide open at an extremely long range (50-80 miles), and moderate woods at long range (30-50 miles), we should get around 1ft horizontal, and 2ft vertical. GLONASS helps here also.  Good for wetlands delineation, preliminary planning, rough stakeout, as well as GIS collection and utility mapping. EpochEtymology: Medieval Latin epocha, fixed point Accuracy vs. Precision

30 The first question we have to ask ourselves is what accuracy are we looking for? o 0.10 ft. - With a couple epochs (1-5) in the wide open at a moderate range (20-30 miles) we can get around 0.1ft horizontally, and 0.3ft vertically.  Good for ground topo and rough control, and rough stakeout (due to the elevations) o Better than 0.10 ft.– With a couple epochs (1-5) in the wide open at a moderate range (20-30 miles), and repeating the measurements on each point every couple hours with a different satellite configuration, we can get better than 0.1ft horizontally, and 0.3ft vertically  Good for control points, panel points, monitoring. Accuracy vs. Precision

31

32 How can I see the iNET stations?

33 Real Time Network Fundamentals Shane “Trap” Traffanstedt Earl Dudley, Inc Thanks for attending


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