On two recent jobs, before full leaf, I decided to see what I could get done using the GPS equipment (Hiper Pro, base and rover setup, each on 2 meter poles). Generally, I was impressed by what I could get done in a given amount of time. However, on each of these two recent jobs, I've gone back to do some additional work with the Total Station (Sokkia SRX3) and my backsight doesn't check out. Excessive difference on vertical. About 0.4 feet, which seems reminiscent of the height of phase center above the mounting point. I think I'm doing something wrong but I don't know what it is. For each of these jobs, I have set up the base over a nail, the coordinates of which are unknown, take a ROUGH BASE, and run a static session on the reciever. Later, I submit the static log file to OPUS (height = 2 meters), and receive coordinates for the nail in return. Good solution from OPUS. Then I translate my field work to the OPUS BASE.
I'm using Carlson SurvCE in the field, with the Hiper Pro receivers and with my Sokkia SRX.
I'm posting my raw data files (GPS and TS) below to see if any of you have a suggestion based on what you see. Could it be because I don't have a geoid file loaded onto the DC? Thanks for any and all suggestions.
Al
*****************************************************************************
RAW FILE - GPS SURVEY
JB,NM*********,DT04-24-2015,TM11:06:57
--MO,AD0,UN2,SF1.00000000,EC0,EO0.0,AU0
--SurvCE Version 4.03
--CRD: Alphanumeric
--MA Mainland NAD83
--TS Scale: 1.00000000
--Scale Point not used
--EDM Mode: Fine
SP,PN1,N 5000.0000,E 5000.0000,EL100.0000,--MAG NAIL
--DT04-24-2015
--TM11:18:16
--MA Mainland NAD83
--Equipment: Topcon, HiPer Pro, SN:T309-0284
--Localization File: None
--Geoid Separation File: None
--Grid Adjustment File: None
--GPS Scale: 1.00000000
--Scale Point not used
--Base Configuration by Reading GPS Position
--DT04-24-2015
--TM11:18:16
--Entered Base HR: 6.5617 ft, Vertical
--Antenna Type: [HIPER_PRO],RA0.0763m,SHMP0.0285m,L10.1060m,L20.0971m,--Topcon Internal
--BP,PNBP001,LA42.092425084133,LN-73.260161693810,EL196.5442, AG2.0000,PA0.1060,ATAPC,SRBASE,
--GS,PNBP001,N 2888083.8561,E 131882.0373,EL637.9193,--Base
--GT,PNBP001,SW1841,ST490445000,EW1841,ET490445000
--GPS Log File: BRODERICK base open Topcon,HiPer Pro
--GNSSLOGRCVR,FLBRODERICK,SRBASE,RNT309-0284,RMTPSHiPer Pro,RF3.5 Dec,24,2010
--GNSSLOGANT,FLBRODERICK,AN,AMHIPER_PRO,LI15000,AG2.000,PA0.106
--Antenna Type: [HIPER_PRO],RA0.0763m,SHMP0.0285m,L10.1060m,L20.0971m,--Topcon Internal
--GPS Scale: 0.99993427
--GPS Scale Point N:2888024.17751785 E:131926.60988130
--DT04-24-2015
--TM13:20:52
--RTK Method: RTCM V3.0, Device: Cable or Generic Device
BP,PN_0000,LA42.092425084200,LN-73.260161693900, EL196.4382,AG2.0000,PA0.1060,ATARP,SRROVER,--
--Entered Base HR: 6.5617 ft, Vertical
LS,HR6.9094
GPS,PN2,LA42.092425084200,LN-73.260161693900,EL196.544200,--ROUGH BASE
--GS,PN2,N 2888083.8601,E 131882.0343,EL637.9193,--ROUGH BASE
--Entered Rover HR: 6.5617 ft, Vertical
LS,HR6.9094
GPS,PN3,LA42.092214149675,LN-73.260179629852,EL196.750837,--8" nail
--GS,PN3,N 2887870.6887,E 131863.6873,EL638.5973,--8" nail
--GT,PN3,SW1841,ST498159000,EW1841,ET498170000
--Valid Readings: 10 of 10
--Fixed Readings: 10 of 10
--Nor Min: 2887870.6729 Max: 2887870.7070
--Eas Min: 131863.6773 Max: 131863.6945
--Elv Min: 638.5704 Max: 638.6170
--Nor Avg: 2887870.6887 SD: 0.0117
--Eas Avg: 131863.6873 SD: 0.0054
--Elv Avg: 638.5973 SD: 0.0124
--NRMS Avg: -3.2808 SD: 0.0000 Min: -3.2808 Max: -3.2808
--ERMS Avg: -3.2808 SD: 0.0000 Min: -3.2808 Max: -3.2808
--HRMS Avg: 0.0419 SD: 0.0044 Min: 0.0351 Max: 0.0476
--VRMS Avg: 0.0509 SD: 0.0029 Min: 0.0465 Max: 0.0547
--HDOP Avg: 0.8232 Min: 0.8232 Max: 0.8232
--VDOP Avg: 1.3286 Min: 1.3283 Max: 1.3289
--PDOP Avg: 1.5630 Min: 1.5627 Max: 1.5632
--Number of Satellites Avg: 14 Min: 14 Max: 14
GPS,PN4,LA42.092152699872,LN-73.260159184650,EL196.565327,--top bank
--GS,PN4,N 2887808.1489,E 131877.6730,EL637.9886,--top bank
--GT,PN4,SW1841,ST498232000,EW1841,ET498232000
--HRMS:0.046, VRMS:0.051, STATUS:FIXED, SATS:14, PDOP:1.630, HDOP:0.878, VDOP:1.374, TDOP:1.112, GDOP:1.973
GPS,PN5,LA42.092176881723,LN-73.260173136135,EL196.449856,--top bank
--GS,PN5,N 2887832.8605,E 131867.7220,EL637.6098,--top bank
--GT,PN5,SW1841,ST498250000,EW1841,ET498250000
--HRMS:0.032, VRMS:0.055, STATUS:FIXED, SATS:12, PDOP:2.104, HDOP:1.031, VDOP:1.834, TDOP:1.493, GDOP:2.580
*************************************************************************
TOTAL STATION SURVEY
JB,NM*********,DT05-17-2015,TM16:24:50
--MO,AD0,UN2,SF1.00000000,EC0,EO0.0,AU0
--SurvCE Version 4.03
--CRD: Alphanumeric
--MA Mainland NAD83
--Equipment: Sokkia Robotic, SRX Series, SN:100867
--TS Scale: 1.00000000
--Scale Point not used
--EDM Mode: Fine
--P.C. mm Applied: -7.0000 (Sokkia 360:foresight)
--Temperature = 80.00F Pressure = 991.00HPA
OC,OP1,N 2888076.30389,E 131884.52954,EL737.033,--OPUS BASE
LS,HI5.1900,HR5.4000
BK,OP1,BP3,BS184.5509,BC184.5508
BD,OP1,FP3,AR184.55080,ZE89.39130,SD213.990000,--8" nail
BR,OP1,FP3,AR4.55210,ZE270.20590,SD213.990000,--8" nail
--SS,OP1,FP3,AR184.55080,ZE89.39070,SD213.990000,--8" nail
--Calculated: AR184°55'09", HD213.960, Z737.711
--Measured: AR184°55'08", HD213.986, Z738.123
--Delta: AR0°00'01", HD0.027, Z0.412
LS,HI5.1900,HR5.3000
SS,OP1,FP512,AR111.2449,ZE89.3308,SD25.290000,--edge disturbed earth
SS,OP1,FP513,AR97.4628,ZE89.1701,SD31.040000,--edge disturbed earth
Just a couple things When setting up my hiper v and tesla I have the option to change my HI from vertical to slant. Sounds like if your using a fixed rod at 6.562 then you want your HI to be vertical. Check topcon manuals to be sure. Other thing it maybe time to get the SRX calibrated. I am sending in my topcon ps which is pretty much the same gun right now to get calibrated because I started getting bad back sight vertical checks.
It may be the receiver height you sent to OPUS, check and see what OPUS wants to use. There are some diagrams that show it. The 2 meters might not be the #.
Thanks for the suggestions. As for receiver height, I think I should use vertical, and I think I did use vertical in fact. I've been getting very good results, both horizontal and vertical, with the SRX, so I don't think it's a calibration issue.
I'm pretty sure the antenna reference point (ARP) for the Hiper Pro is the bottom of the 5/8-11 threads, the flat plane which rests on the top of the tripod. And, if that's the case, then the height is 2 meters.
Height Errors Shoud Balance Out With Same Equipment
0.4' may be as good as it gets with short observations.
To check with a total station one should have three static GPS points.
I do not believe your low DOPs as reported. Send me your static RINEX files and I'll give you an expanded opinion.
Just because there were no leaves, do not ignore trees. In spring the sap starts flowing long before the leaves sprout.
Paul in PA
When surveying with a rover using a scale factor as I have, does the scale factor affect Z?
Have you tried swapping your base and rover position on the two points? It could be that there is something goofy in the antenna model in the software. I have seen it with with Survce, hiper II base, and grx rover.
The basic rule is check, check, and re check.
RTK gps being off by 0.4 feet, would not surprise me.
Static GPS, near some sort of multipath, could also do that.
What do you think? Also, what about your Total Station? Did you swap ends with it yet? look at the trig leveling math. Do it manually. Don't fully trust a data collector, as it can have goobers in it's program. Offsets. Vertical offsets.
You present your problem. But, those things are find-able, by checking all things.
N
Have you checked into a NGS vertical benchmark? Are you sure you have the correct antenna selected in the data collector, with the right offset?
It shouldn't at all, it is designed to be applied to the horizontal numbers. I would be very concerned that I have .4' vertically, that is way too much, I'd expect to see under .05' on a small survey.
Many things can effect it of course, mostly due to measures of heights, I see you don't have a Geoid model applied, I always apply one, and I see you are on an assumed coordinate system, I would rather do it on a projected system, much easier to track GPS info that way.
I can't Imagine a Geoid making .4' of difference in a short distance, but I would see that in less than a mile here.
The data file shows identical heights for base and rover. They could both be wrong and you are still going to check in good. It's something else. I would suspect it's the data treatment for the RTK.
Do you have any software that will post process your RTK? Carlson does some funky stuff and can produce strange results. My suggestion is store and process vectors. That should eliminate or identify most problems...
A Geoid model can be over 0.40' differences. In the Houston area between Geoid99 and Geoid09 it is half a foot difference. Which is why it is important to have the Geoid model on any topo.
Yes, for sure, but he isn't applying a Geoid model, at least that's how I read it.
It would be unusual for the raw ellipsoid heights to vary from the Geoid by over .4' in a short distance, in other words: a Geoid model height of 40.2' at point A and a geoid height of 40.6' at point B.
I will see changes in geoid heights differences of .1' per 1000' but I don't think it's that way in Mass.
In that case, if you were just using ellipsoid heights, in 4000' you would see a separation between a total station elevation and GPS elevation of .4' and none of the data would be wrong.
I do own a license of Trimble Business Center, and it has the ability to process RTK vectors, I believe. But, I'm not sure I've saved enough data in the field to be able to do that.
Height Errors Shoud Balance Out With Same Equipment
I sent PM to you earlier. I think the DOP values are correct. Wide open sky for most shots. 0.4' is too much in my experience.
Here is a link to the RINEX file:
https://www.dropbox.com/s/jfdqgm0myz1bkgg/BROD114q.15O?dl=0
Here's a cut/paste of the beginning of the file. What does the line in RED mean?
2.11 OBSERVATION DATA M (MIXED) RINEX VERSION / TYPE
Topcon Link 8.2.3 18-MAY-15 21:19 PGM / RUN BY / DATE
build November 09, 2012 by (c) Topcon Positioning Systems COMMENT
*********_AI2O MARKER NAME
MARKER NUMBER
-Unknown- -Unknown- OBSERVER / AGENCY
8QH6E9YAI2O Topcon -Unknown- REC # / TYPE / VERS
-Unknown- -Unknown- ANT # / TYPE
1350195.3889 -4538910.8037 4258656.1724 APPROX POSITION XYZ
2.0000 0.0000 0.0000 ANTENNA: DELTA H/E/N
1 1 WAVELENGTH FACT L1/2
2015 4 24 16 16 0.0000000 GPS TIME OF FIRST OBS
2015 4 24 20 13 15.0000000 GPS TIME OF LAST OBS
15.000 INTERVAL
16 LEAP SECONDS
28 # OF SATELLITES
7 C1 P1 P2 L1 L2 D1 D2 # / TYPES OF OBSERV
G 3 661 661 661 661 661 661 661 PRN / # OF OBS
G 7 227 191 191 227 191 227 191 PRN / # OF OBS
G 9 547 531 531 547 531 547 531 PRN / # OF OBS
G14 380 380 380 380 380 380 380 PRN / # OF OBS
G16 950 950 950 950 950 950 950 PRN / # OF OBS
G19 332 331 331 332 331 332 331 PRN / # OF OBS
G21 20 0 0 20 0 20 0 PRN / # OF OBS
G23 839 815 815 839 815 839 815 PRN / # OF OBS
G25 223 223 223 223 223 223 223 PRN / # OF OBS
G26 943 942 942 943 942 943 942 PRN / # OF OBS
G27 572 569 569 572 569 572 569 PRN / # OF OBS
G29 498 467 467 498 467 498 467 PRN / # OF OBS
G31 858 858 858 858 858 858 858 PRN / # OF OBS
G32 508 503 503 508 503 508 503 PRN / # OF OBS
R 1 782 781 781 782 781 782 781 PRN / # OF OBS
R 2 653 634 633 653 633 653 633 PRN / # OF OBS
R 3 287 284 282 287 282 287 282 PRN / # OF OBS
R 7 176 176 176 176 176 176 176 PRN / # OF OBS
R 8 506 506 506 506 506 506 506 PRN / # OF OBS
R 9 166 163 154 166 154 166 154 PRN / # OF OBS
R10 620 615 615 620 615 620 615 PRN / # OF OBS
R11 950 950 950 950 950 950 950 PRN / # OF OBS
R12 549 547 547 549 547 549 547 PRN / # OF OBS
R19 297 288 282 297 282 297 282 PRN / # OF OBS
R20 613 609 609 613 609 613 609 PRN / # OF OBS
R21 620 620 620 620 620 620 620 PRN / # OF OBS
R22 366 366 366 366 366 366 366 PRN / # OF OBS
R23 41 41 41 41 41 41 41 PRN / # OF OBS
SE TPS 00000000 COMMENT
END OF HEADER
15 4 24 16 16 0.0000000 0 13G 3G14G16G25G29G31G32R 1R 7R 8R 9R10
R11
22820359.423 7 22820360.42245 22820368.51745 119921804.775 7 93445564.75345
7214.566 5621.747
21551129.265 8 21551129.17746 21551134.11246 113251945.672 8 88248271.74946
3405.745 2653.829
24490932.084 7 24490932.21545 24490944.84445 128700731.485 7 100286280.19945
9329.281 7269.570
22480726.708 7 22480726.40146 22480734.88646 118137014.040 7 92054817.36546
2537.808 1977.497
23811739.942 6 125131527.916 6
7017.157
20380108.399 8 20380108.27747 20380111.92147 107098190.852 8 83453141.08647
5008.530 3902.756
21456873.013 8 112756630.929 8
4453.061
21709025.838 7 21709024.247 7 21709033.176 6 116047206.956 7 90258948.466 6
8778.649 6827.841
21526973.297 8 21526973.469 8 21526977.513 7 115235586.042 8 89627668.792 7
1512.872 1176.691
19410035.641 8 19410037.503 8 19410038.960 7 103939900.272 8 80842145.007 7
5060.819 3936.201
21749396.205 7 21749396.848 7 21749399.956 5 116140594.239 7 90331567.647 5
2086.264 1622.617
19481831.129 8 19481833.847 8 19481839.763 7 103849167.925 8 80771572.722 7
4892.402 3805.210
21529044.499 7 21529043.283 7 21529051.323 6 115044728.735 7 89479234.896 6
8085.037 6288.383
Regarding sending your ps In for calibration on blown backsight verticals. If this is done robotically, there is a calibration procedure you can do to recenter the robot eye to match the crosshairs.
Just found this out after a 2 mile (non-robot) traverse that closed vertically to 0.018, and yet the robot backsight is blown by almost 0.20 when we return to the site.
I will get a geoid loaded for future jobs. I had one loaded before, then got a newer data collector (a Surveyor +) and hadn't yet taken the time to load one. I think it measures ellipsoid height instead of orthometric height as a result of the fact that a geoid is not loaded. The difference is about 100 feet I guess, because I had to lift my shots about that much.
Thanks, Nate.
I've been using the total station alot, and using Carlson's SurvNET to process my work, horizontally and vertically. The results are simply amazing to me. I am very confident in the total station measurements, and would expect that the error is less than 0.02'.
Thanks for the suggestion to swap base and rover. It is a good one. I'll give that a try and post the results.
I have not checked in to an NGS benchmark. I will check the settings in the DC.
