Comparison of L-Band Correction Services for Survey and Land-Based Applications

At Blue Planet Geomatics, we’re committed to helping customers find the best solution for their unique applications. The available L-Band correction services vary by land, marine and air. This article discusses the available L-Band correction services for land-based applications, including:

 

Positioning Solutions

There are three primary solutions available: Real Time Kinematic (RTK), Differential GNSS (DGNSS) and Precise Point Positioning (PPP).

• Generally speaking, RTK is the fastest (no convergence time) and most accurate but requires you to set up your own base station. RTK is extremely limited in range (usually <40km of range from your station).
• Most DGPS/DGNSS uses the worldwide stations of your provider. DGPS/DGNSS is usually faster than PPP and ranges in accuracy depending on your package. DGNSS has higher monthly costs because the service provider has to maintain a large number of stations.
• PPP is often the cheapest solution and available globally. Prices increase significantly with higher accuracies and it’s the slowest system with the convergence speed depending in part on the accuracy required.

Survey and Mapping

RTK is the first choice for many surveyors. RTK can provide accuracy up to a few centimeters at high speeds, however, alternatives are increasing in popularity.

There are growing public and private Real Time Networks. Real Time Networks function similarly to RTK but use a permanent set of stations. This simplifies surveying by eliminating initial site selection, RTK setup and potential station problems, and may increase accuracy. RTN, however, is restricted to available areas, additional fees and network congestion.

PPP is another solution that is growing in use. PPP requires no base stations and has no range restrictions, eliminating site selection, setup and potential station problems, without paying additional RTN fees and is available everywhere. PPP is now also able to achieve centimeter-level accuracy, but is slower at high accuracy levels with higher monthly costs.

Agriculture

For many agricultural applications, RTK is often the preferred choice. While there is a higher initial cost, it provides unmatched speed and accuracy. For most agricultural applications, including heavy equipment operation, range restrictions are not a problem.

RTK based L-Band correction services are ideal for farm mapping, soil sampling, seeding and planning, automated steering, yield monitoring and mapping, spraying and harvesting.

Mining, Oil & Gas

In applications for mining, oil, and gas, there are several considerations that will factor into your decision.

• Level of Horizontal and Vertical Positioning Accuracy
• Stability and Reliability of Signal Reception
• Vehicles and Vessels
  • How many are there? How fast are they going? How are they operated?

• Type and Nature of Mobile Equipment Installation
• Type of Installation
  • Is it permanent or short-term? This will influence the placement of cables and location of antennas.

Applying RTK, PPP, and DGNSS solutions in the mining, oil, & gas industries all have their own sets of advantages and disadvantages. Given the characteristics of these solutions, the preferred one will depend on the activity. The optimal solution may differ among activities such as drill guidance, asset tracking (of lighting plant and mobile generators for example), access and zone control for visiting vehicles, collision avoidance, fleet management, etc. because the considerations for each one varies.

Rail

For the rail industry, DGNSS is the preferred L-band correction service for its applications.

While GNSS has been widely utilized in marine (link to blog post), aviation (link to blog post), and vehicle navigation, it has only begun to be implemented in rail transport systems around the world. This is due to the fact that this industry operates under stringent safety regulations and possesses unique characteristics that aren’t present in other applications. For example, the unavailability of satellite signals when a train enters a tunnel or passes through a cutting or densely built-up area has prevented the use of GNSS in safety-critical applications (e.g. train control and signaling).

When used in conjunction with other sensors, computers, and communication systems, GNSS can greatly enhance safety, accuracy, and effectiveness.

Examples of railway applications:

• Management of Rolling Stock
• Movement Tracking of Locomotives
• Collection of Passenger Information
• Level Crossing Approach
• Cargo Tracking Signalling
• Asset Tracking

Correction Services

OmniSTAR

With four different DGNSS solutions, OmniSTAR offers plenty of options for coverage:

• OmniSTAR HP
  • Requires a dual frequency receiver
  • 10 cm at 2-sigma (95%)
  • No need for local base stations

• OmniSTAR G2
  • Short-term accuracy of 1-2 in
  • Long-term repeatability of 10 cm or better, 95% CEP
  • Includes GLONASS satellites and correction data, useful in situations with limited satellite visibility (terrain, buildings, and vegetation)

• OmniSTAR XP
  • Requires a dual frequency receiver
  • Short-term accuracy of 1-2 in
  • Long-term repeatability of 10 cm or better, 95% CEP
  • Slightly less accurate than OmniSTAR HP but has global availability

• OmniSTAR VBS
  • L1 only, code phase pseudo-range solution
  • Typical 24-hour sample will show a 2-sigma (95%) of significantly less than 1m horizontal position error
  • 3-sigma (99%) horizontal error will be close to 1 m
  • Ideal in situations where repeatability and accuracy are not the primary concerns

NovAtel CORRECT

NovAtel has also specialized in all three services.

• NovAtel’s RTK solution provides accuracy of 1 cm + 1 ppm horizontal and 1 cm vertical (baseline range ≤ 40 km).
• Novatel’s DGNSS service provides 40 cm accuracy at ≤ 100 km of range.
• Two Novatel PPP solutions:
  • TerraStar-C has an accuracy of 4 cm RMS horizontal and 6.5 cm RMS vertical with a 20 to 40-minute convergence time
  • TerraStar-L has an accuracy to 40 cm RMS horizontal and 50 cm RMS vertical with a convergence time of < 5 minutes.

Hemisphere Atlas

Atlas provides three PPP solutions:

• H10: 8cm 95%, 4 cm RMS horizontal accuracy, 12 to 20-minute convergence time
• H30: 30 cm 95%, 15 cm RMS horizontal accuracy, 4 to 5-minute convergence times
• H100: 1m 95%, 50 cm RMS horizontal accuracy, close to instantaneous convergence

For land and survey applications that are able to work within a limited range but require a very high level of accuracy and no convergence times (e.g. safety-critical applications), RTK solutions would be ideal if you are able to set up a base station.

DGNSS is similar to RTK in that you need a base station and it doesn’t take any time for its convergence. But it is ideal in applications where a larger range is necessary and decimeter-level accuracy is sufficient.

PPP is the most economical solution and provides high accuracy (centimeter to decimeter-level). However, it requires a longer period of initialization and convergence than RTK and DGNSS solutions. Thanks to its global availability, PPP L-Band correction services would provide tremendous benefit to applications that operate within a large range (e.g. geological mapping).

 

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