They won't ever do a township retracement east of the Rocky states will they? Only where they stopped allowing minerals to be patented. You didn't qualify that you only mean in the jungle. ?????ÿ
There are a mountain of townships retraced (1980-2020 era) and somewhere in the early 2000's GPS took over for that. Maybe the total station was broken out along the Powder River a few times, but probably not often.?ÿ
They won't ever do a township retracement east of the Rocky states will they?
Already did a number of them back in the 90's.
I'm saying that Javad has a system right now, that could retrace a whole Township, with confidence. In Arkansas, Louisiana, Mississippi, Ozarks, etc
That's here now, today.
Nate
NMEA
https://en.wikipedia.org/wiki/NMEA_0183
Take a survey grade receiver, it's a challenge to "downsample" that into NMEA or GPX files for the mapping grade vicinity and trail map applications. Basically the basis for my questions. On the way to the survey can I collect data for OpenStreetMap with the T-3 on the chariot, and, hiking in, can I map the trails in a useful way? Sounds like a yes on both.
How does this black magic work when there are almost no gaps for satellite signals to get through? I??m not experienced enough yet as most of my work is with the robotic in subdivisions where i need the short distance accuracy.?ÿ
I have gotten some tricky shots with the r10 and Sokkia grx2 by taking several longer shots with the same point number using weighted average and breaking my lock in between shots. Works sometimes other times not.?ÿ
What was the reason for the retracement; are there large federal tracts left in Arkansas?
How does this black magic work when there are almost no gaps for satellite signals to get through?
If it is not totally pitch black under the trees then light is getting through. And if light is getting through there are gaps that satellite signals can also get through. It is then just a question of a) weak signal, and b) filtering out "noise".?ÿ
The biggest problem under trees is not signal strength, but multipath where the travel times from the satellites are not consistent.
@norman-oklahoma Wait a minute, are you saying satellite signals follow the same path as light? I've always thought light reflects so that we have indirect light. Satellite signals reflecting become useless.
Well, if not useless, at least degraded. The signals do reflect to some extent. There are tricks that the receiver designers can do to try to capture the earliest arrival, not the average arrival, of each signal, but that's mitigation not cure.
Wait a minute, are you saying satellite signals follow the same path as light?
If you look up from under a tree you will see some blue. Some direct light does get through.?ÿ Your cell phone will work. Your am/fm radio will receive. And so some direct satellite signal also gets through.
waiting for someone to put a fisheye lens camera centered in the antenna, that can see the unobstructed sky and use that as part of the QC process.
waiting for someone to put a fisheye lens camera centered in the antenna, that can see the unobstructed sky and use that as part of the QC process.
I saw a study years ago where that exact process was done to evaluate the amount of cover when testing recievers.
I'll look to see if I have a copy.
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If you look up from under a tree you will see some blue. Some direct light does get through.?ÿ Your cell phone will work. Your am/fm radio will receive. And so some direct satellite signal also gets through.
You're conflating very different frequencies and modulations and assuming clear sky view is required for any RF propagation. Not the case, am/fm, and to a lesser extent cell phone frequencies do not require direct line of sight.?ÿ High power AM, HAM, SSB can girdle the globe if propagation is favorable.
GNSS signals (and most SATNAV signals) approach Gigahertz frequencies and are light-like in that any occlusions block or reflect the signal given it is extremely weak because of orbital distances.?ÿ Clear line of sight for GNSS signals is critical for determination of first arrival and subsequent rejection of reflections through software algorithms; it's scary how complex that is to do.?ÿ I'm skeptical that under heavy canopy a?ÿ survey GPS instrument?ÿ is reliable enough to deliver sub 1/10 foot results, but others claim otherwise.?ÿ Fair enough; I don't doubt that GPS gear is better nowadays but there's a limit.?ÿ
@mike-marks I helped a skeptic prove your point back in 2016 (GPS/Glonass only at that time).?ÿ He was putting together a continuing ed seminar on why it was still necessary to use conventional survey on jobs with stringent requirements such as some government specs..?ÿ He had to change the seminar a bit.?ÿ Matched all his points less than a tenth.?ÿ Least squares analysis met same spec as his conventional.?ÿ
But there does have to be a way to analyze the repeatability while occupying the point.?ÿ For paying work I use procedures that are a bit quicker and settle for tenth and a half at 95%. Still, most of these types jobs around here would be done conventional 1/5000-1/10,000, showing about a foot misclosure the old fashioned way.?ÿ So quite an improvement.
I find canopy is no longer the major challenge.?ÿ Buildings, urban canyon, troposphere (low thick clouds heavy with water) are more of an issue.?ÿ Woods boundaries robot doesn't come out, but topo under a forest of 100' pines, or small lake cottage jobs with lots of locations of improvements the robot is still essential.
..... jobs around here would be done conventional 1/5000-1/10,000 .....,
I agree that RTK can beat that almost always. But 1:10,000 just would not fly around here. Nor would control points to a tenth.?ÿ Not for the work I'm doing.?ÿ I haven't done a closure calculation in?ÿ ... forever .... but I'm looking to weed out residuals that exceed 0.02' or so.
troposphere (low thick clouds heavy with water) are more of an issue.
????ÿ Although increased water vapor in the lower troposphere does slightly increase signal attenuation it's trivial compared to the overall attenuation budget.
It is true that dtrop,?ÿ caused by refraction in the troposphere results in delay,?ÿ nearly none if the satellite is overhead and significant at lower elevation angles which is one reason why observing sats below 15?ø elevation is not recommended.?ÿ An immediate consequence of being a non-frequency dependent delay is that the tropospheric refraction can not be removed by combinations of dual frequency measurements (as it is done with the ionosphere).
Therefore, the only way to mitigate tropospheric effect is to use models and/or to estimate it from observational data. It does have a dry component and a wet component. The dry component which contributes most of the delay, perhaps 80% to 90%, is closely correlated to the atmospheric pressure. The dry component can be more easily modelled?ÿ than the wet component.?ÿ Autonomous positioning accuracy can be affected not using a correction model [see below].?ÿ Differential procedures nearly eliminate the dtrop contribution and the wet component contribution becomes trivial.
Therefore I assert that "low dark clouds heavy with water" are not an issue when using survey grade receivers in differential mode.
@norman-oklahoma Of course. Depends on the job requirements.
@mike-marks In my experience what I stated is undeniably true.?ÿ But considering your theory, if the dry component can be modeled in a few seconds or minutes, but the wet can not, then would the wet component not be more of a problem??ÿ I don't know, the textbooks say the troposphere and local multipath are basically the only remaining challenges.?ÿ Sometimes I don't even bother going out if there's low thick clouds anymore, because i know it will take much longer than normal to get acceptable solutions.?ÿ It's also known that water is a major contributor to signal interference.?ÿ
At any rate, my main point is that it is possible under the right conditions, and with right equipment and procedures, to achieve results similar to conventional means in a fraction of the time. Of course I charge more for it because I can deliver faster:)
IMHO the category list on this site is in the neighborhood of excessive. I do however agree with having pretty much all the current categories but there comes a point where too many categories can become detrimental.?ÿ
Despite my above opinion, maybe admin should consider creating one more category for ??Field Equipment?.?ÿ
That way anyone wishing to hear how the Javad gear is superior to all other manufacturers can click on the Field Equipment category. And those who don??t want to discuss that can avoid it.
To distinguish itself from ??Software, CAD & Mapping? category, ??Field Equipment? could be focused on data collectors, total stations, gps, rods, hammers, tape measures, shovels and other peripheral gear.?ÿ
