GNSS Network Concept
Using GNSS surveying or specialized receivers for maps connected to the Caribbean GNSS Network provided by Global Matrix Engineering, will provide exact infrastructure information such as the location of sanitary and storm registers, inverted elevations, pole location and electrical and telephone infrastructure. , hydrants, cadastral surveying and topography, among others can be located and incorporated into a database and infrastructure GIS (Geographic Information Systems) governmental or private.
GNSS Network RTK requires a recommended minimum of five reference stations (there is no maximum) with an inter-station spacing of up to 70 km. The reference stations are usually permanent installations and form the RTK GNSS Network, which is the backbone of the Network RTK principle.
Caribbean GNSS Network operated by Global Matrix Engineering is the most powerful internet broadcaster of Real Time GNSS (RTK Net) correction messages for different applications in the Caribbean. It’s the only one creating single base and network corrections overseas including Dominican Republic, Puerto Rico and US-BVI Virgin Islands. GNSS Receivers such as Ashtech, Asus, Carlson, Geomax, Field Genious Leica, Magellan, South, Trimble and Topcon among others, with RTCM 3.0, 2.3, CMR+, CMR-, Leica format compatibility and internet capabilities can benefit of broadcaster services.
The principle of Network RTK begins with all reference stations within the RTK Network continuously streaming satellite observations to a central server running GNSS Network RTK software, such as Leica GNSS Spider.
The aim of GNSS Network RTK is to minimize the influence of the distance dependent errors on the rovers computed position within the bounds of the network. The Network RTK server software begins this process by:
- Fixing the ambiguities of the satellites (being observed by the reference stations) within the network.
- Using the data from all (or a subset of) reference stations to generate corrections that are sent out to the rover.
- The next figure shows The Principle of GNSS Network RTK.
1. The rover connects to the Network RTK server via a one-way or two-way communication link (e.g. radio modem, GSM or Internet). Once the rover receives the RTK data it computes its position using the appropriate algorithm.
2. Which algorithm the rover uses, and how the distance dependent errors are minimized is very much dependent on the Network RTK method being used.
3. Previously we mentioned MAX, FKP and Virtual Reference Station (VRS) as examples of GNSS Network RTK methods available in the market – each of these methods minimizes (or models) the errors in different ways. Depending on the method, this modeling is either carried out on the Network RTK server or at the rover. Therefore, the relationship between the RTK Network and the rover is different for each method which can lead to significant differences in performance, accuracy, reliability and traceability for the rover.
The establishment of Caribbean GNSS Network by Global Matrix produces multiple benefits, but there are four that we would like to highlight:
1. Reduced Operating Costs
When working within the RTK Network, the need for the establishment of a local GPS Base Receiver and Base Radio will be eliminated. This allows the use of a single person field crews that can begin work within minutes of arriving on site. When you do a job with less people, less equipment, no setup times, no equipment guards, no teardown time and eliminate radio link problems, your operating costs will be greatly reduced.
2.Ease of Operations
One-man crews can now travel anywhere within the GNSS RTK Network. Coverage of the GNSS RTK Network will be all Internets driven. Rovers will call into the network via mobile phones. All calls will be routed via socket connection into a single server. This server will be able to handle all incoming Rover calls without the need for dedicated telephone lines. If you have cell coverage and are located inside the network, you will have access to the real time corrections messages.
One-man crews can now work with Puerto Rico State Plane Coordinate System NAD83 and MSL using the official NGS Geoid 2012b. In Dominican Republic can now work with UTM-19 North zone and MSL using the WGS84 EGM 2008 Geoid without tedious post-processing procedures. All survey works will be in the same coordinate system, geospatially ready for any government agency or private industries requirements.
GNSS Network Apps
Using a “GNSS Survey Grade” or “Mapping” GPS receiver connected to Caribbean GNSS Network powered by Global Matrix Engineering, high accurate infrastructure information such as manhole rims locations, manholes inverts, electric and telephone poles and infrastructure locations, fire hydrants, boundary and topographies surveys, among others can easily be located and incorporated into a private or government organization’s GIS (Geographic Information Systems) infrastructure.
Developing a solid and reliable GNSS network is not a simple task. A substantial investment in hardware, software and a very sophisticated Information Technology (IT) infrastructure is needed to make the network an engineering and geomatics master piece. Global Matrix has spent more than 0.7 Millions of US Dollars and more than 10 years in research and development in regard to network connectivity, monitoring and management. In fact, new and integrated IT Team developed solutions to ensure the integrity of the network and to provide an extremely reliable service for our clients. Our company employs the best professional staff of Engineers and Land Surveyors that provide direct support to the operation and maintenance of the GNSS Network.
Land Survey - Geomatics
In the Caribbean Global Matrix GNSS RTK Network infrastructure provides increased production and accuracy for all types of surveying and mapping necessities by providing long range coverage for RTK GPS. Regardless of the application, production is increased by eliminating the need for setups temporary static observations and inefficient GPS base stations and using a short range conventional radio such as Pacific Crest or Trim-Talk Radios.
GIS (Geographic Information Systems)
GIS data collection initiatives are extremely enhanced with the RTK- GNSS Network infrastructure. Data collection is performed more accurately and efficiently by having wide area coverage. Data that is collected by hand-held “GIS” grade GPS receivers can be post processed with the RINEX data provided by each RTK- Network GNSS reference station. Post processing to a nearby reference station provides higher accuracy with less occupation time. By utilizing a “Survey Grade” GPS receiver connected to Caribbean GNSS Network, high accuracy data, such as manhole rim elevations, pipe inverts among others can easily be collected and incorporated into an organization’s GIS infrastructure.
GPS RTK-Net infrastructure provides increased production and efficiency for many phases of construction projects. From construction stakeout to site excavation and grading, RTK Network enables projects to be completed in less time and with less error. RTK- GNSS Network provides high accuracy geodetic control over large geographic areas. For contractors utilizing machine guidance systems, connection to RTK Network significantly reduces grading errors, allows an operator to grade more efficiently and work on several projects simultaneously without the need for a temporary GNSS base station at each project site. Surveyors connected to the RTK Network with corrections messages are able to respond more quickly and accurately, reducing down time for the contractor to turn in, saving money and efforts.
RTK- GNSS Network infrastructure enables aerial photography and LIDAR project to be accurately completed with minimal effort from land surveyors on the field. Aerial photography for photogrammetric jobs is planned around weather and foliage. By having a continuously island wide operating network of GNSS reference stations , flight crews can deploy quickly to take advantage of good flying weather. Rapid aerial mapping is often required by government officials to properly assess certain situations such as a natural or man-made disaster. By having a RTK- NSS Network infrastructure, emergency mapping can be more easily accomplished. Each reference station is set to record data at a one (1) second sampling rate. The photogrammetrist can then process the data to accurately compile the aerial mapping.
Construction of large engineering structures such as dams, bridges, and high-rise buildings, is essential for the development of the Caribbean However, under excessive loading, such structures are subjected to deformation, potentially causing loss of lives and property. Hence, the safety of these works, especially dams, demands periodic monitoring and in-depth analysis of their structural behavior, based on a large set of variables that contribute to the deformation. In fact, the deformation itself forms the most relevant parameter to be monitored. Several factors contribute to the deformation of these structures. The most important of all is the result of the varying stresses and strains developed in structures due to the effects of local crustal movements. Crustal movements cause shifts in the relative location of points situated on the dam body and in the vicinity of the dam. Other contributing factors include type of construction materials, wind forces, temperature variations, settlement of soil, and fluctuations in the load due to vehicular traffic.
The use of RTK GNSS in Hydrographic Surveying provides a vertical reference datum for all shallow and deep waters depth measurements eliminating errors introduced from heave, vessel squat, and tidal fluctuations. As a result, before and after dredging surveys are completed more accurately and more efficiently. During survey or dredge operations, the use of RTK GNSS water levels eliminates the need for shoreline support personnel to take tide staff readings. The accuracy of RTK also reduces the allowable over-depth dredging which can save millions of dollars in dredging costs.
Disaster Relief Response
Often, critical utility structures such as valves, manholes and fire hydrants need to be located to protect and or redirect a utility system. An RTK Network reference station infrastructure provides first responders accurate reference data to pinpoint the location of critical structures. Because survey ground control is not needed any more, responders can recover facilities quickly. Once the flood waters have receded, utility structures are often buried in mud. By utilizing a RTK GNSS rover, it is possible to determine the depth of excavation required to find the utility structures, thus expediting restoration of the utilities for to the citizens.