Guide to CPOS
CPOS is a positioning service that allows you to accurately calculate your position down to the nearest centimetre. The service enables you to map, record and retrieve everything - to the nearest centimetre.
CPOS is used by professional GNSS users who want to save time and money by streamlining their work. After receiving a username and password from us, one can easily connect via the internet and start work in just a few minutes. It is also a nationwide service. If you have a CPOS subscription, access to ETPOS (post-processing data) will also be included in the price.
Areas of use/application
CPOS is well suited for use in many different areas within the fields of surveying, roads and construction, forestry and agriculture. Examples of use and user groups: Mapping and surveying property boundaries, recording and retrieval, in construction machinery, in the mining industry, in agricultural and forestry machinery for fertilising/sowing, in e-works and for nautical mapping.
Type of subscription and pricing
The CPOS service has different types of subscription. Subscriptions are tailored to different applications, and the choice of subscription depends on how you intend to use CPOS.
- CPOS virksomhet (enterprise) is purchased through distributors/equipment suppliers who have a distribution agreement with the Norwegian Mapping Authority.
- CPOS test is for new customers who wish to test CPOS free of charge for a period of 1 month.
- CPOS standard (surveying) is the type of subscription that is most relevant to the majority of users.
- CPOS fast (fixed installation) can only be used for fixed installation in mobile user units (e.g. excavators, dredging boats, drilling rigs, drones etc.).
- CPOS landbruk (agriculture) is a subscription for agricultural use (important aid in precision agriculture; auto control enables the farmer to reduce the driving load, reduce environmental emissions, and ensures that each plant is treated as individually and optimally as possible).
- CPOS undervisning (teaching) is offered free of charge to all schools for use in teaching activities.
- CPOS utland (abroad) is an additional subscription for existing CPOS customers who also require positioning services in Sweden. The Norwegian Mapping Authority orders the SWEPOS subscription via Lantmäteriet (the Swedish mapping, cadastral and land registration authority), and the customer will receive an email with connection information etc. The customer must make sure that they have a mobile telephone subscription/SIM card that is compatible with mobile data usage in Sweden. The subscription is invoiced via the Norwegian Mapping Authority.
How CPOS works
The CPOS service consists of correction data that is received in real time via an internet connection to the Norwegian Mapping Authority’s servers. Based on received corrections, the user’s GNSS receiver can accurately calculate their position at all times.
Independent of mobile base stations (RTK)
The CPOS system calculates a virtual reference station (VRS) based on data from permanent geodetic stations and the user’s position. The user’s rover equipment will perceive the VRS data as if they were data from a nearby physical base station. Therefore, a separate base station is not required.
User equipment requirements
In order to receive corrections, the following is required:
- GNSS receiver: Multi-frequency with input for RTCM format V2.3 or V3.1, and NMEA format output (GGA)
- Modem: Mobile connection with GPRS/4G or broadband/wireless network internet connection.
CPOS is available via the internet. Regarding mobile distribution (GSM/4G), it is assumed that the customer has a telephone subscription (such as a mobile data subscription) with a telecommunications company. Therefore, the costs of the telephone subscription and automatic message counting are additional.
The service covers mainland Norway. For use in Sweden, a separate subscription must be purchased for the corresponding service. The subscription can be ordered via our order form.
CPOS maintains specified accuracy within the coverage range, provided that other surveying conditions allow for this. The service requires a connection to the Norwegian Mapping Authority’s servers from the location where the user intends to conduct surveying/measuring.
Within the service’s coverage range, the expected achievable accuracy is as follows:
|In areas with approximately 35 km between SATREF PGS||In areas with approximately 70 km between SATREF PGS|
|Horizontal EUREF89||8 mm||14 mm|
|Height EUREF89 (above ellipsoidal height)||17 mm||30 mm|
|Height NN2000||20 mm||36 mm|
The results are based on the Norwegian Mapping Authority’s analysis of measurements carried out with CPOS. The figures in the table above are listed for 66% of cases (standard deviation 1 sigma). In order to get the values for 95% of cases (2 sigma), you need to multiply by 2.
The expected initialisation time is similar to that of measurements taken with traditional RTK equipment. Achievable accuracy depends on atmospheric and local conditions, as well as the quality and setup of the user equipment.
The following conditions may prevent the satellite signals from reaching the antenna and/or may cause problems in achieving specified accuracy:
- Conditions that cause the satellite signals to be reflected before reaching the antenna
- The GNSS receiver’s ability to eliminate reflected signals
- Atmospheric interference, such as ionospheric activity in solar storms and similar
- The number of visible satellites and their position/geometry
- The GNSS receiver’s ability to calculate positions
Correction data is given in RTCM format in official reference frame EUREF89/NN1954/NN2000.
The ‘Real-Time Positioning Services’ (in Norwegian) standard deals with requirements for GNSS-based real-time services. The Norwegian Mapping Authority must adhere to the standard both as the infrastructure owner and the service provider. The standard shall provide users with an opportunity to assess the quality of the various positioning services. The CPOS documentation (in Norwegian) highlights how the Norwegian Mapping Authority meets the standard’s requirements.
The Norwegian Mapping Authority’s height reference model, HREF
The Norwegian Mapping Authority has developed height reference models to safeguard the transition between ellipsoidal heights in EUREF89 and national heights in NN1954/NN2000. For large parts of the country, the accuracy of this transition is better than 2 cm. The HREF models are freely available and can be entered manually in the field book or received along with the CPOS corrections.
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