Hi Harrison, How many “known” points have you tested? How where those point position calculated. They could be off. If you are using state geodesic monuments, try to find the documented precision of the monument. States have different types of monuments, some are very old and have different standards. Make sure the geodesic point is not the problem. Make sure the coordinates are in the right CRS. As an example, if the coordinates are published in NAD83 original but you are assuming NAD83(CSRS), then you have a problem. When converting from the monument’s CRS to NAD83 UTM zone 10N, are you using the correct grid files? What is the published precision for this reprojection?
You say you have houses and trees. This could be the problem. Find a geodesic point that is in the middle of a field or on the side of a highway with no obstacles. Make sur your observations will be done when the constellation is well distributed in the sky. I believe Trimble has a observation planing software that can help you figure out the best time for observation. This could explain why the GEoTX are to the east unless the observations where made at the same time and same conditions (ex leaf off). What post processing techniques are you using? How far is the base station from your unit? If you are using a state correction service, can you select more stations? How long are the observations? Have you tried other methods of post processing like PPP? Have you contacted Trimble? Have you looked on there site to see if there is a software update (firmware) for the unit or the post processing software? Nicolas Cadieux https://gitlab.com/njacadieux > Le 8 mars 2021 à 05:24, Springfield Harrison <stellar...@gmail.com> a écrit : > > > Hi Kirk, > > Thanks again for the ideas. > > Re "I assume your raw data files are being converted to gpx on a computer > since the raw terrasync files are proprietary binary files". Not sure why > you would make this assumption - PFO does not export GPX files, only GIS > files of many kinds, although one could create a custom format I suppose. > > I have always avoided non-GIS formats (Garmin, GPX, GDB, KML, KMZ, > GoogleEarth, iPad/Tablet "mapping", etc.). I'm in the process of re-mapping > a tablet based tree inventory using SW Maps with a Total Station survey as > many of the trees are near the property boundary. Some of the tablet errors > are quite large. Due to the tree canopy, GPS quality is variable. > > I know that many people use tablets and hiking GPS as mapping tools but I > have little faith in them for that purpose. > > For many years my work flow has been: Trimble Receiver + RTCM/SBAS -> > Pathfinder Office [+ RINEX Post Processing] -> SHP files -> GIS (QGIS or > Manifold GIS). The CRS is NAD83 UTM 10N throughout, for my home area at > least. > > None of these steps offer any option to choose or modify the Base Station CRS > so I don't think that would be the culprit in my NW data offset, although > maybe I've missed something. > > Last fall I collected quite a few points in an attempt to quantify the > problem, if that's what it is. Here are some summaries: > > Average distance from "Known" point (m) > > Location > > Receiver Correction Corner IP NW Grand Total > GeoXT Post 1.44 1.44 > SBAS 1.37 1.26 1.33 > Uncorr 0.73 > 0.73 > GeoXT Total 1.34 1.26 1.32 > ProXR RTCM 0.38 0.61 0.49 > ProXR Total 0.38 0.61 0.49 > Grand Total 1.17 0.97 1.12 > > > > > Location Data > > > > Count of Feature Points and Positions > > Corner IP NW Total Count of Point_ID Total Sum of > Filt_Pos > Receiver Correction Count of Point_ID Filt_Pos Count > of Point_ID Filt_Pos > GeoXT Post 9 1492 9 1492 > SBAS 8 1280 5 905 13 2185 > Uncorr 2 2836 > 2 2836 > GeoXT Total 19 5608 5 905 24 6513 > ProXR RTCM 4 2541 4 683 8 3224 > ProXR Total 4 2541 4 683 8 3224 > Grand Total 23 8149 9 1588 32 9737 > > > Corrected test Points and separation from the antenna location. > > <malbiblkchcpcpdh.png> > > > > As above but with 2 uncorrected GeoXT points overlaid, including the > individual positions that were averaged. > > <jpbjaanipeilbbgo.png> > > Notes and findings: > > Site is open sky but with house and trees adjacent > Antenna is static, occupation periods long (5 sec logging interval) > 32 observations averaged from 9737 positions > some observations are with the GeoXT internal antenna, others are with a > Trimble aircraft antenna (intended for SBAS) > Work flow as outlined above > The GeoXT uncorrected results are better than either of the corrected > results!? > The corrected ProXR results are better than any of the GeoXT results, > although biased to the east > The uncorrected GeoXT readings exhibit the NW bias but to a lesser extent > which seems to indicate that the correction does not create the problem but > may exacerbate it, if that makes any sense. > I have probably missed something but my reaction remains that the receiver > may be defective (?) > Thanks again for your help and patience . . . . . > > ----- > Cheers, Spring > > >> On 07/Mar/2021 03:54, kirk wrote: >> Hi Springer. >> >> I assume your raw data files are being converted to gpx on a computer since >> the raw terrasync files are proprietary binary files. If you are using >> trimble pathfinder, you can post process differentialy correct the data if >> you have access to base station logged at the same time you captured your >> field data. Having a base station 100 miles away will not improve your >> results as the baseline is too long. >> >> I do not know if you can write a gpx file directly from pathfinder but I >> would not bother. I would write a shapefile which will contain the >> coordinate system you specify. Simply open in qgis and you should be good >> to go. If your older unit works better, I would expect it may be an issue >> with the setup within pathfinder or perhaps the software version. >> >> I think your consistent offset is a direct result of how you are converting >> your data from trimble to gpx. >> >> As I mentioned in my previous comments, there are many issues which affect >> accuracy. Just because the box says it is accurate you will rarely >> replicate that in the field. >> >> In terms of WAAS dataframes, these are processed internally on your field >> unit. >> >> Kirk Schmidt >> >> >> >> Sent from my Galaxy >> >> >> -------- Original message -------- >> From: Springfield Harrison <stellar...@gmail.com> >> Date: 2021-03-07 5:57 a.m. (GMT-04:00) >> To: kirk <k...@nortekresources.com>, Jorge Gustavo Rocha >> <j...@geomaster.pt>, qgis-user@lists.osgeo.org, Greg Troxel >> <g...@lexort.com>, Dan <19dm...@gmail.com>, Nicolas Cadieux >> <njacadieux.git...@gmail.com> >> Subject: Re: [Qgis-user] Trimble GeoXT 2005 Accuracy >> >> Hello All, >> >> Thanks for the comments, I'll reply more fully tomorrow. >> >> The receiver is Trimble mapping grade: >> >> "The GeoExplorer 2005 series consists of: >> • The GeoXH™ handheld, providing subfoot (30 cm) accuracy, or even 8-inch >> (20 cm) accuracy >> with the optional Zephyr™ antenna. >> • The GeoXT™ handheld offering submeter accuracy for GIS data collection and >> data >> maintenance. >> • The GeoXM™ handheld with 1–3 meter GPS accuracy for mobile GIS >> applications." >> >> "Post processed carrier accuracy: 1-30cm". This receiver was probably >> $5-8000 (?) new. >> >> Data collection was stationary, open sky, good satellite coverage, several >> minutes of 5 sec observations, good PDOP >> SBAS and/or post processed >> The concern is not the accuracy as such, but the systematic NW shift. This >> has been observed over several months, consistently. My old Trimble ProXR >> (1994?, $20K new!) is actually better in this regard than the GeoXT! >> >> The Trimble manuals make no mention of the SBAS CRS, implying "turn it on >> and go, the receiver will integrate the SBAS into the rover file." >> >> More tomorrow, thanks . . . . . >> >> ----- >> Cheers, Spring >> >> >> >>> On 06/Mar/2021 15:56, kirk wrote: >>> A few notes. >>> >>> sbas which is waas in north America is based on equatorial satellites which >>> will get you in the 1 m range in southern Canada. >>> >>> you can achieve sub decimeter accuracy consistently using rtk ,either >>> through a ntrip caster (base station) broadcasting over the intenet or >>> with your own base station and a radio link. there are a few chip sets and >>> break out boards that you acquire and assemble your own system. This is a >>> very inexpensive option. >>> >>> Another option in Canada is to use precise point positioning (PPP) which >>> requires 6 to 12 hours of observation data using L1, L2 or L1 and L2 data >>> and rinex log files. This comes in handy if you need to establish a remote >>> base station. >>> >>> A proper antennae with a metal ground plane is also critical to getting >>> quality results. >>> >>> Observing under a forested canopy is difficult especially in summer under >>> leaf on conditions, after a rain which creates multiparth mayhem. >>> >>> There is a reason survey grade equipment is relatively expensive. If you >>> require repeatably accurate results in a variety of conditions this is an >>> option. >>> >>> Kirk Schmidt >>> >>> >>> >>> >>> >>> >>> >>> Sent from my Galaxy >>> >>> >>> -------- Original message -------- >>> From: Jorge Gustavo Rocha <j...@geomaster.pt> >>> Date: 2021-03-06 6:41 p.m. (GMT-04:00) >>> To: qgis-user@lists.osgeo.org >>> Subject: Re: [Qgis-user] Trimble GeoXT 2005 Accuracy >>> >>> Hi, >>> >>> I just jump in this thread to say I'm really impressed with Ardusimple. I >>> have a RTK Handheld Surveyor Kit [1] for +- 400 € and it works really well. >>> >>> I use the national NTRIP service and I have consistently precisions around >>> 10 cm with just one receiver. >>> >>> I use a free Android application called SW Maps [2]. My survey points, >>> tracks and photos are collect in a geopackage that I can read in QGIS. I >>> use it mostly to collect ground control points for my drone flights. >>> >>> Regards, >>> >>> Jorge Gustavo >>> >>> [1] https://www.ardusimple.com/product/rtk-handheld-surveyor-kit/ >>> >>> [2] https://play.google.com/store/apps/details?id=np.com.softwel.swmaps >>> >>> Às 20:12 de 06/03/21, Greg Troxel escreveu: >>>> Springfield Harrison <stellar...@gmail.com> writes: >>>> >>>>> Thanks Dan. See my relies to Kirk and Greg. The Emlid sounds >>>>> interesting, will have a look. >>>> I have an earlier Emlid Reach (not RS or RS2), which has L1 only, and I >>>> never got it to work well. >>>> >>>> Also look at the Ardusimple unit -- but it's more a parts kit than a >>>> system. You need a way to get RTK reference data in, and a good >>>> antenna. One approach is Vespucci (OSM editor for Android) as a >>>> datalogger, and the Ardusimple WiFi NTRIP master to get corrections over >>>> the phone's hotspot. >>>> >>>> https://www.ardusimple.com/product/simplertk2b/ >>>> >>>> >>>> _______________________________________________ >>>> Qgis-user mailing list >>>> Qgis-user@lists.osgeo.org >>>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >>>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >>> -- >>> >>> Geomaster >>> Jorge Gustavo Rocha | Software Engineer >>> e: j...@geomaster.pt | m: +351 910 333 888 >>> g: 41.54094,-8.40490 | v: 510 906 109 >>> a: Rua António Cândido Pinto, 67, 4715-400 Braga >>> >>> >>> _______________________________________________ >>> Qgis-user mailing list >>> Qgis-user@lists.osgeo.org >>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
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