I'm a fresh graduate and new to LSU, i'm learning how to use the epoch 25 rtk.I have read some manuals but still couldnt use it effectively and it seems complicated.I would like to know if my procedure of starting the rtk survey is the right way.
My procedure:
First step, after setting the instrument up (both the base and the rover receiver), i would connect the data collector to the base, open the survey pro and open a new job from the file menu,give a name to it,then the system will ask if i would like to retain the previous projection which include the datum and zone.Then i would accept the projection, since that is what i want, then a page comes up, where i can fill in;point name,coordinates (N & E),Elevation and description.I would provide the coordinate and elevation of the point where the base is set up if they are readily available or i feed it with handheld gps coordinate and elevation of the base receiver point and that would be all for the new job file.
Second step, i would go to job menu, tap setting and configure the base receiver and also the radio,the medium i use for base-rover communication.
Third step, still connected to the base receiver, i'll go to survey menu and tap on "set base",where i will provide the height of the base receiver and click ok, a page will show up where i can check a radio button to either set the base on existing point or on a new point, i do not really understand this part well, if i set it on existing point and access the point from the list,the point on the new job file shows up and i'll tap on it but can't remember if the system always accepts that point or not,because most often i go for "set the base on a new point" and from there,the system will take me to a page where i need to configure the rover. I would remove the data collector from the base, connect to rover,configure it.Then to Survey menu,tap on"set the rover",the system will automatically get the base position,after that, the height of the rover is fed to the system and i tap ok. Then,it would ask me to perform resection to 1 or 2 controls to solve horizontal controls and 3 controls for vertical, this atimes make me to give up because of non availability of that numbers of controls.
Now;
1) I want to know if the procedure is right to perform RTK, and if not, could someone help me out.
2) If one feeds in coordinates and the system says the specified point is out of the coordinate system or grid map,what does that mean.
3) Is there any much difference between the RTK and Post processing survey.
4) Does it mean rtk gps cannot work on a site where control points are not easily to come by.
5) Which is better to use between ground coordinate & map coordinate projections.
Pls, i need your help guys.
Replies
Hello Akin,
Always when first using a GPS on a new site if out of the box or moving from one area several miles from the last or several days since last used you want to let the GPS receivers set out in the open for 30 to 45 mins to update the ephemrus..this updates the receivers to current time and zone. Then start by setting up the base first, on your control point.
CONTROL POINT this is the information your have brought in from out of the area, unless you are lucky to have control onsite. ..or use random point
As you are setting up the base lets get it working and transmitting, with data collector.
Then set up the Rover, as you do this you should be able to see if the Rover is receiving data from the base. If these lights are blinking or on it tells you they are communication for RTK. If there is a problem as you get to this then we have to find that issue.
In a area of population some times other can be on your freq and you have to check to see which freq is clear.
after getting to this point then we can proceed forward with setting up your project.
The two things I think i am understanding about your problem is:
1. coordinance- if your entering coords from a hand held it is going to be very in accurate to start with. If you dont have control near your site you have to back up and and find it and bring into the site, if you want horz. and vert. control. Unless your just using a autonomous positioning
2. the other issue of asking you for 3 vert. points sounds like its asking you to calibrate to the site.
Hope this gives you another piece of advise coming from a non TDS user but just general set up methods so you can isolate your problem. These other guys have given you some great advise as far a details in the software.
I'll keep an eye on this to see how you progress, hope it helps.
There are two basic shortcuts I use to staking out coordinate points with RTK.
1. Set up RTK on random point and initalize the base, which basically localizes the base to within a few meters depending on base. Now go find a point you have a coordinate for, eg, centerline intersection or property corner, and localize the rover to it, if rotation is not geoditic then find another point for bearing or specify rotation. With TDS the second point will either create a scale factor or if you use for bearing only it will split the difference of the two points for the point of rotation, I like to hold the point closer to the job, so first I record the second point and inverse or stake out the first (the stakeout program will give you a distance to the stakeout point, so by occupying the 2nd point it will give a good distance, based on specified scale factor, to the point being staked out), get a good distance, then recalculate the second point using the correct distance so my scale factor is very close to one. Now TDS will still split the distance for the point of rotation, but the position should match much better to the holding monument. Now the GPS is translated, rotated and scaled, stake!
The second method requires the plan in CAD, which you will translate and rotate to your localized geoditic position (not absolute, unless you static locate the base first or are on a known geoditic point)
2) set up RTK without localizing the rover, go and record whatever record points you can find, or existing improvements you need to match. Drop the points in CAD, bring in your drawing with calculated layout points as a block, rotate the block and do a "best fit" to the found points then explode block write ascii file from points (or you could just calculate the layout points at this point, if you didn't before) drop back in data collector, load into job file, stake.
PS For the 1st method Carlson allows you to use second point for rotation only and specifiy scale.
The 2nd method may require scaling
Hi Akin
the steps you use is correct
second question on the out of tolerance is due to the derived point in autonomous position and the given control value is morethan 30 meter when compare to the Ellipsoidal height. this error message can be ignored
third question relate to accuracy. as always post process result is always better than RTK results
4th question is for conducting RTK survet you need atleast one control point. therefore prior to making RTK survey you must establish control point with Static survey for an accurate RTK survey.
map coordinte projecting is always needed for local cnstruction purpose
Hey there Akin. My name is Matt. We are using Epoch 50 units with Survey Pro software. I believe that the steps to set up and start collecting data will be the same with the 25 unit and the 50 unit. I may be wrong. But we definitely start up our GPS bases and get started at collecting data differently. We set up and connect to our base and rover through the Survey menu>Start base. Of course, after starting a job and giving coordinates for a base point. Start base>Select Reciever>Input the Antenna height and then tap next once the base reciever locates itself. Aftere tapping next, the screen will come up where you select the base point. Most times the base will automatically set itself on the correct point, but this screen gives you the option to double check or change it if you need to. Tap next once the base point is correct. Now you will select your Rover reciever and input the height of the antenna. Tap next and once it gets "Fixed", you will here 2 tones, then you are good to go. Granted, i'm writing this while in the field on my cell phone, so I may have left out a thing or two. I don't know if this helps you or not. If you need me to clear it up for you or maybe break the steps down more, feel free to email me at [email protected].