Topo Point vs Rapid Point

With the default Measure Topo method, the software checks the observed epoch positions (however many you have set to collect in your survey style) against each other and gives you a warning if any are out of tolerance.

There's nothing to check against with Rapid Point, so (theoretically) there is a higher likelihood that you will end up with a bad shot.

However, practically speaking (especially with modern receivers like the R10/R12 which are continually checking the solution quality) using Rapid Point when satellite conditions are good is just fine. I have used it quite a bit for gathering ground shots on open sites, and can't really remember ever having a truly "bad" shot. At least none that would throw one-foot contours enough to squirrel up a design topo.

I compare Rapid Point to using Tracking mode + Single measurement on a total station - no redundant observations to check against, but if procedures and conditions are good you're almost certainly getting good enough data for most dirt work.

I was using an R8s the other day with a TSC3 running Access 2016 on NC's VRS network. I don't like doing such but this was more a test in a back parking lot than actual work. After fooling with the observed control method I swapped options to topo just to play with it some more & noticed the rapid point option. Was not sure how reliable the rapid topo shot would be with a fully optioned/scaled R8s or not? I noticed the topo shot option would stop in the midst of a shot if the precision cut out (underneath a big bradford pear tree).?ÿ

Sorry, but I do not use Trimble GPS, hardware or software, so I cannot render an opinion on precision of their short observations.

For the majority of my work I find LIDAR contours are sufficiently accurate for ground work and take EDM shots on buildings, curb, utilities and special features.

I would suggest a comparison of your rapid shots against LIDAR contours would be a reasonable endeavor. LIDAR contours near buildings are mostly off because of the smoothing of the contours, but with hard shots at the corners linework is easily revised.

Paul in PA

Rapid Points are confined to rough measurements, raw dirt topo mostly.?ÿ

I wouldn't use it to collect a value for a boundary corner unless it's done a number of times and evaluated from there.?ÿ

The rapid point works best when you have a long fix time. Much like topo in PPK the longer the unit is fixed the better the location is for each point. Continuous topo is a series of rapid point collections whether it's done RTK or PPK the best results are from the longer sessions.?ÿ

Hello, thanks for getting back to me, I appreciate your insight. I've been researching in the manual,talking to our Trimble dealer and other surveyors here. One of our lesser experienced crews did a design topo for a roadway/bridge project that had some unusual errors. I've spent nights and weekends here trying solve this puzzle while meeting the engineering departments deadline. The project consists of both robotic?ÿ collected on hardscape and GPS for desert terrain. There is improved roadway on either end and a wash where the bridge is going to be built tying the road together. One of the things I found was that Rapid Point was used, in the data collector under Roving Precision the Auto Tolerance was checked off with a horizontal tolerance of .16 and vertical tolerance of .26 elected. In Survey Styles under Rapid Point the Auto Tolerance was checked on. So I found out that the user can go into options at the time of the shot and change the defaults. In any event I've been tracking down two sets of errors that occurred I believe at the two base station set ups. Thank God for raw measurement. Rover we were using R10s for the wash and picking up the edges for an overlap to the hardscape. It was mostly in open area with some desert trees which most would consider more like bushes. They were using TSC7 with the R10 dirtman and did loose lock near trees having to take offset shots. Yavapai County has contours to compare to Paul, thanks for your suggestion. Maricopa County indexed all of their PLSS corners which is published and somewhat maintained, it also lists NGS monuments. Thanks for the info Moe, it does not seem useful if its name represents its intent. Thanks Again for sharing your experiences, I always learn something here. Respectfully,

@rlshound

Maricopa County!

I traveled there often, I can't think of much I saw an R-10 couldn't handle, rapid point or topo point.?ÿ

If you said central NC or something I could see the issue but not Maricopa County.?ÿ

The tolerance needs to be dialed down, do some testing, get comfortable with it.?ÿ

Shoot some points near then under canopy with the total station, then collect the same with the R-10. If I get into a dead area I simply have to either come back later or pull the TS out. I've noticed a marked improvement later in the day when it's being pushed.

Posted by: @rlshound

One of the things I found was that Rapid Point was used, in the data collector under Roving Precision the Auto Tolerance was checked off with a horizontal tolerance of .16 and vertical tolerance of .26 elected. In Survey Styles under Rapid Point the Auto Tolerance was checked on. So I found out that the user can go into options at the time of the shot and change the defaults. In any event I've been tracking down two sets of errors that occurred I believe at the two base station set ups. Thank God for raw measurement.

Oof, we run into this fairly regularly. Crews that are "experienced" and "know all about" working with GNSS. Then they change settings on the fly (fine if you know what you are doing), flub the setup, force-store points with poor precisions, and then forget to keep good notes...

I have to keep reminding the crews that the tolerance settings are there for a reason, and with proper procedure they'll get good data.

For topo points (not rapid) I tend to keep the Occupation Time set to zero, the Number of Measurements set to 3 or 5, and then make sure Auto Tolerance and Auto Store Point are checked. With the R10s and R12s, you can leave them static over a point, even when precisions are not quite there yet, and tell it to start measuring. As the solution improves, it will start measuring as soon as it can, then once the required number of epochs are measured at required tolerance, it will store the point. Keeps you from having to fiddle around as much and re-measure points.

?ÿ

My parents live in Prescott. I really love that area - it was tough to not be able to travel there this year. I could survey all day long in that climate...