On October 1, the U.S. federal government shut bottomward and furloughed 800,000 non-essential workers. While casework advised capital remained active, those advised non-essential services, like the National Geodetic Survey’s Online Accession User Annual (OPUS), were shut down. OPUS is a free, online GPS post-processing service. If you try to admission www.ngs.noaa.gov, the afterward awning will be displayed:
For those of you who await on OPUS for GPS post-processing, now is a abundant time to try one of the added seven online post-processing casework accessible and not accountable to the U.S. federal government. Yes! I wrote seven, and the after-effects from those seven are commensurable to OPUS. The added seven, chargeless online GPS post-processing casework are:
CSRS-PPP: Canadian Spatial Reference System, Natural Resources Canada
AUSPOS: Geoscience Australia
GAPS: University of New Brunswick
APPS: Jet Propulsion Laboratory
SCOUT: Scripps Apogee and Abiding Array Centermost (SOPAC), University of California, San Diego
CenterPoint RTX: Trimble Navigation
My aide Mark Silver, architect of the X90-OPUS receiver I wrote about a few months ago, boarded on an accomplishment to run analysis abstracts through anniversary of the online post-processing casework to authenticate that there are free, online GPS post-processing casework accessible accepted that aftermath after-effects commensurable to OPUS. The afterward abode is the aftereffect of his efforts:
By Mark Silver
You are apparently accustomed with the National Geodetic Survey’s OPUS apartment of online column processing accoutrement (OPUS-Static, OPUS-Rapid Changeless and OPUS-Projects.) These casework are able of bearing centimeter-level accession from changeless GPS observations. What you may not apprehend is there are at atomic six applicable alternatives to OPUS.
All are free, accessible to use, accommodate all-embracing coverage, and accomplish decidedly agnate results.
Since anniversary uses a altered baseline apparatus and processing strategies they anatomy an accomplished absoluteness analysis adjoin anniversary other.
IGS orbits and the IGS abiding CORS arrays are acclimated by abounding of the services, about some use proprietary accessories arrays and apogee articles that accommodate added redundancy.
How commensurable are these services? Which one is the best?
Criteria for Comparing
Comparing after-effects is a difficult proposition:
The acknowledgment to all of these questions is “it depends.” Your appraisal will depend on your specific application.
For this evaluation, the afterward rules absolute the abstracts set selection:
This would not be as absorbing afterwards a little competition.
To accumulate the appraisal simple, the sum of the X, Y and Acme ambit will be the annual and the casework will be ranked from everyman annual to accomplished score, with the low annual actuality the ‘best.’
Range was called as an indicator of the accustomed best absurdity that ability be encountered if alone a distinct 24-hour book was observed.
The accumulated ambit rewards a processing arrangement that best estimates delays, interference, alarm errors and added sources of change that occurred during the 32-day trial.
Remember that the every aspect of this ‘competition’ is arbitrary: from the alternative of ascertainment sets, to the final scoring system.
The absolute take-away from this appraisal is not that one annual is better, but how aing all of the casework are to anniversary other.
Two casework (JPS’s APPS, magicGNSS) won’t be adequate to the boilerplate user and a third (RTX Centerpoint) may not assignment for some users based on receiver and antenna support. Details of these problems are presented with the annual descriptions below.
The Analysis Data
SGU1 in St. George, UT USA was called as the ascertainment base. The observations abide of 32 afterwards canicule (May 3, 2013 through June 3, 2013), 24-hour ascertainment files, 30-second interval, GPS alone data. The abstracts files were downloaded from the NGS CORS archive.
Each of the 32 files were submitted to anniversary of the processing casework and the after-effects acquire been archival for X, Y and Ellipsoid Height. All abstracts is presented in IGS08 accustomed aeon affected coordinates. All abstracts has been projected to UTM Meters for these comparisons.
The Boilerplate Values
Remember, the absolute adventure is how aing anniversary of these casework aftermath after-effects to one another. Let’s attending at the boilerplate positions from anniversary annual and the aberration from OPUS:
As you can see in Figure 1 above, the casework were about aural 5mm of OPUS in X, Y and Height.
Position Tracking vs. Time
And the Winner Is…
Following are the scores, based on the aggregate of X, Y and Acme range:
Score baronial (remember this is aloof for fun as the casework provided appreciably agnate results):
There is a cogent affair in the JPL APPS’s appear achievement positions, which will accumulate it from actuality of any use to best users. magicGNSS’s after-effects are decidedly altered than the added services. User’s should apart appraise magicGNSS’s adequacy for their purpose. SOPAC’s SCOUT could not be evaluated because it clearly does not abutment either the receiver or antenna that was acclimated at the analysis site.
AUSPOS: Geoscience Australia
Submittal Page: http://www.ga.gov.au/bin/gps.pl
AUSPOS is a chargeless annual from Geoscience Australia. Admission is via a simple web interface, the antenna acme and blazon are entered forth with a email abode for the alternate abode set. Book acquiescence is via FTP or anon from the web interface.
The alternate PDF abode is the best attractive of the advised casework and includes a Processing Arbitrary assuming a map of the CORS sites that were acclimated in the solution. SINEX files are additionally available.
AUSPOS uses the Bernese GNSS Software for processing baselines, IGS orbits and IGS arrangement stations. Solutions are accessible for anywhere on the earth.
RINEX files charge to be at atomic 1-hour in length, 6-hour files are recommended. Bunched RINEX files are additionally accepted. Files may be aeroemism with UNIX, Hatanaka, ZIP, gzip or bzip compression.
Centerpoint RTX Column Processing: Trimble Navigation Limited
Submittal Page: http://www.trimblertx.com/UploadForm.aspx
CenterPoint RTX Column Processing is a chargeless annual offered by Trimble.It works anywhere in the apple and is based on a proprietary Trimble 100 accepted CORS network. Accuracy is 2 cm with 1-hour of ascertainment data; 1 cm with 24-hours. Files best than 24-hours are not accepted.
RTX uses GPS, GLONASS and QZSS tracked SV’s.
The appear achievement frames accommodate ITRF2008 at accustomed aeon and a user selectable anatomy like NAD83/2011 2010.0. RTX is one of the few casework that will anon consign NAD83 affected results.A distinct folio PDF and a XML aftereffect book are alternate by RTX. Unfortunately, it is not accessible to archetype afterwards after-effects from the read-only PDF aftereffect book to the clipboard.
RTX supports a bound cardinal of receivers (Trimble) and a almost baby subset of IGS modeled antennas. For this test, TEQC was acclimated to being the RINEX headers with a commensurable Trimble receiver to the absolute Ashtech ProFlex 500 receiver that is in use at SGU1. This was all that was appropriate to bluff an accustomed device. If the antenna had not been listed, it would acquire been all-important to bluff the antenna and acclimatize the acme to reflect the aberration in L1 appearance centermost offset.
GAPS: University of New Brunswick
Submittal Page: http://gaps.gge.unb.ca/indexv520a.php
GAPS is an advancing activity at the University of New Brunswick and was developed by the Department of Geodesy and Geomatics Engineering.
File acquiescence is by a web folio and GAPS provides a ample cardinal of user inputs and potentially allows the accomplished akin of customization of any of the advised services:
GAPS alone processes GPS abstracts (no GLONASS.)
Submitted filenames charge attach to the SSSSDDDh.YYt book format. GAPS accepts RINEX and bunched RINEX files, they may optionally be gzip, unix aeroemism or ZIP compressed.
APPS: Jet Propulsion Laboratory
Submittal Page: http://apps.gdgps.net/apps_file_upload.php
WARNING! APPS alone letters the acquired position to the aing decimeter-meter in geographic (lat/lon) coordinates, while advertisement ECEF coordinates to a atom of a millimeter. If you acquire to use APPS, you will charge to manually catechumen the ECEF XYZ to geographic coordinates.
JPL’s APPS is based on GIPSY-OASIS (currently adaptation 5). APPS uses NASA’s 70 Global GPS Arrangement additional densification from added systems (100 absolute receivers broadcast globally.) Solutions are about accessible with 5 abnormal adjournment from observation.
APPS is accessible to use, you aloof specify a book to upload and again bang on ‘Upload’ it takes alone 15 abnormal to get a aftereffect afterwards the book upload is complete. You can optionally annals for a chargeless annual and use email or FTP for aggregate uploads.
APPS additionally has receiver Live Performance Monitoring: (http://www.gdgps.net/monitoring/index.html) which generates a absolute time blueprint of three receivers advance through the world.
OPUS: U.S. National Geodetic Survey
Submittal Page: http://www.ngs.noaa.gov/OPUS/
OPUS solutions are the best accepted PPP Post-Processed band-aid in the United States. Two flavors of OPUS are accessible for distinct points:
Long occupations (6 hours) aftereffect in accomplished accumbent and GPS-derived ellipsoid heights.
The new OPUS-Projects annual processes assorted receivers through assorted sessions to a final candy arrangement adjustment.
CSRS-PPP: Natural Resources Canada
Submittal Page: http://webapp.geod.nrcan.gc.ca/geod/tools-outils/ppp.php
Before appliance CSRS-PPP, you will charge to annals for a chargeless user account.
CSRS has a absurd desktop appliance called PPP-Direct that you can aloof annoyance and bead files onto. PPP-Direct automatically submits the book and saves all typing, abundantly abbreviation the adventitious of error.
CSRS-PPP uses both GPS and GLONASS (if available) observables. Ocean Title Loading corrections can be overridden.
CSRS-PPP will acquire distinct abundance files for processing. CSRS will acquire RINEX and Bunched RINEX, and will break ZIP, GZIP and unix compression formats.
CSRS-PPP has a absurd PDF report, a .csv book account after-effects aeon by aeon and a abundant apparatus clear arbitrary file.
The desktop acquiescence tool, accompanying with the abundant achievement letters fabricated CSRS-PPP my admired tool.
Submittal Instructions: http://magicgnss.gmv.com/ppp/
magicGNSS Blog: http://magicgnss.gmv.com/wordpress/
magicGNSS accepts emailed files and allotment solutions by email. Turnaround time is fast and appearance a nice PDF abode additional SINEX, receiver alarm bent files, tropospheric delay, KML aisle and RINEX CLK alarm bent files.
Static and kinematic files with observations from GPS, GLONASS are candy by magicGNSS and the annual reportedly Galileo-ready.
magicGNSS uses a subset of IGS stations to accommodate amount coverage.
SCOUT: Scripps Apogee and Abiding Array Centermost (SOPAC). University of California, San Diego
Scout accepts RINEX and bunched RINEX files, aeroemism (Z, gz, ZIP) submitted from an FTP armpit or pushed assimilate a provided FTP server.
Files charge be generated on a bound subset of receivers and antennas. While the IGS antenna and receiver files are the base for adequate devices, not all IGS-listed accessories are on the acceptable accessory list. SCOUT affidavit accurately warns adjoin bluffing accessories and antennas.
SCOUT uses the GAMIT processing engine.
Because the analysis abstracts for this commodity is from a bottomless receiver and the appointment action requires a FTP host server with bearding admission which best users will not bother with, the achievement from SCOUT was not evaluated.
The affinity of after-effects amid all of the casework I candy is amazing. That they alter alone by millimeters demonstrates the robustness of the algorithms and processes they use.
The aberration amid AUSPOS, RTX, GAPS, OPUS and CSRS-PPP solutions are negligible. For important accession projects, it assuredly makes faculty to use them all.
For locations in the United States, OPUS and RTX acknowledgment NAD83-2011 affected results. Alone OPUS allotment acquired orthometric heights appliance GEOID12A. While OPUS has added ancestry than the added services, it is accessible abundant to abide important observations to assorted casework as a absoluteness analysis for important positions.
As you apprehend from Mark’s abode above, alike admitting OPUS is shut bottomward until the U.S. Congress can dness its differences, don’t let that stop you from processing your GPS changeless sessions. However, some akin of due activity on your allotment is bare as requirements alter for anniversary service. For example, changeless sessions for the OPUS-RS annual can be as abbreviate as 15 account while added casework crave two hour GPS changeless sessions. Furthermore, some casework action GPS L1 abstracts while others crave both GPS L1 and GPS L2 observations.
See you aing month.
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