AT-AT Project Survey Control and GNSS Reference Network

Synopsis

AT-AT requires consistent positioning across its highway corridor so that construction plans, ground surveys and aerial mapping align.

We propose a shared project survey control network supported by permanent GNSS reference stations. Participating teams would access corrections through an interoperable service, with documented coordinates, retained observations and independent verification.

A proof of concept will verify the relationship to existing construction control, equipment compatibility, positioning accuracy and service continuity before full deployment.

The challenge

Teams currently work with different local coordinate systems along the corridor. The challenge is to connect those systems to a common, documented reference while preserving the relationship to approved construction plans.

The solution must combine verified ground control and elevation benchmarks with the GNSS correction service. Highway-survey guidance establishes project control as the basis for subsequent surveys and requires GNSS localization to connect to adjusted control.

Engineering precedent: Caltrans Control Surveys, §9.4-3 · Caltrans Construction Manual, §3-5. These references do not establish AT-AT contractual requirements.

Proof of concept

The PoC will demonstrate that the proposed solution provides consistent, repeatable positioning for ground survey teams and the Aerial Intelligence team.

1. 01

   Verify existing control

   Independently check selected control points and elevation benchmarks against project records.

2. 02

   Establish the common reference

   Document the agreed horizontal and vertical references, projection, units and grid-to-ground treatment. Verify their relationship to existing construction systems and Mexico’s official geodetic framework.

3. 03

   Deploy pilot stations

   Test selected installations, including mounting, communications, power and observation recording.

4. 04

   Validate accuracy and interoperability

   Compare repeated measurements from different equipment against independent checkpoints excluded from calibration. Test representative corridor conditions, station transitions and the longest baselines. Compare single-station and network RTK/VRS services where available.

5. 05

   Test continuity and traceability

   Verify outage recovery, alerts and retained RINEX observations suitable for independent processing.

6. 06

   Approve deployment

   Independently review results against accuracy, repeatability, availability, recovery and interoperability criteria agreed with the client before testing.

The reference specification will document the connection to INEGI’s geodetic framework. NTRIP supports open distribution of corrections; compatibility with the equipment used on AT-AT will be demonstrated during testing. Elevation checks will use leveling or total stations where construction tolerances require them.

INEGI RGNA · BKG NTRIP documentation · phased testing and repeated checks: NGS advisory draft guidelines.

Establishing and auditing the station coordinates

Each station needs verified coordinates before it becomes an operational reference. We propose static processing with Natural Resources Canada’s CSRS-PPP, followed by independent checks and a documented connection to project control.

CSRS-PPP works worldwide, including Mexico. It is distinct from NOAA’s OPUS, which uses differential processing against reference stations. A PPP solution provides a geodetic position; it does not establish AT-AT’s construction elevations or validate existing local systems by itself.

1. 01

   Document the installation

   Assign a station identifier. Record receiver and antenna models, serial numbers, firmware, antenna reference point, orientation and measured offsets to the monument. Confirm the antenna calibration model before processing.

2. 02

   Record repeat sessions

   Proposed commissioning target: two complete 24-hour sessions on separate days, with the installed antenna unmoved. Retain one-second raw observations where supported, observation and navigation files, and a log of gaps or interruptions. Duration is a project proposal, not a CSRS-PPP requirement or an accuracy guarantee.

3. 03

   Process and review PPP

   Check RINEX headers, supported signals and antenna offsets. Submit each session in static mode using the ITRF output option. Save the full reports and inspect convergence, uncertainties and warnings. Use Rapid or Final satellite products for the review and record which products and reference realization were used.

4. 04

   Check independently

   Compare repeat sessions in the same reference frame and epoch. Independently process simultaneous baselines using suitable INEGI RGNA or IGS stations and test checkpoints excluded from calibration. Resolve discrepancies before accepting the coordinates; agreement between two bases alone does not establish accuracy.

5. 05

   Define the project reference

   Document the agreed WGS84 realization and coordinate epoch, with the processing reference and any required transformations. INEGI publishes RGNA coordinates in ITRF2008, epoch 2010.0; these cannot be compared directly with current-epoch PPP results. Verify construction elevations against AT-AT’s benchmarks. UALI will assess processing and local-system integration.

6. 06

   Approve, configure and archive

   The appointed geodetic specialist prepares the station coordinate report for independent review and AT-AT approval. Configure the approved coordinates using the receiver’s specified reference point. Retain original RINEX files, processing reports, field records and configuration exports. Subsequent coordinate changes require a documented review and a new version.

Each station’s antenna model, calibration identifier and physical reference point will be documented and used consistently in RINEX records, processing and receiver configuration.