On This Page

Overview Product Details Specifications Frequently Asked Questions Requirements Product Resources How to Buy Program Area Copyright Printer-friendly Version

Overview

BCACSm

The BCACSm is a system which provides GPS corrections in post-mission and real-time using the standardized Provincial coordinate system NAD83 (CSRS). Real-time communication is supported via a UHF radio link and/or wireless PCS link (i.e. cellular telephone). Real-time accuracy levels range from approximately 1m (using RTCM code corrections and a mapping grade GPS receiver) to centimetre level (using dual frequency survey grade receivers). It provides users with the ability to survey and layout points, accurate to a few centimetres, instantaneously.

BCACSm has been implemented in three municipal areas:

In addition to the BCACSm - CRD Service, other regional governments and municipalities (e.g. Kelowna, Kamloops, Prince George, Comox-Strathcona Regional District, etc.) are in the planning stages and are expected to soon follow the lead of the Capital Regional District and the MV.

BCACSm Capital Regional District

The Capital Regional District (CRD) and Base Mapping and Geomatic Services Branch (CRGB) are working in partnership with selected private companies to build this system to support high precision real-time GPS applications within the CRD. Other regional governments and municipalities are in the planning stages and are expected to follow the lead of the CRD.

The BC ACSm - CRD provides the capability to acquire precise control anywhere within the CRD without the requirement to have two GPS receivers or using  costly traversing to bring control in from distant monuments. All the user needs is a single GPS receiver capable of achieving the accuracy they require, and an off-the-shelf radio receiver. Subscriptions to the correction signal can be obtained from the CRD.

Goals, Objectives, and Vision of BCACSm - CRD

The principal goals of the BC ACSm - CRD are:

"the establishment of a high accuracy and consistent real-time Global Positioning System (GPS) based geospatial referencing system in the Capital Region District, in support of surveying, engineering, mapping, Geographic Information Systems (GIS), land information management, socio-economic data capture and management, and precise vehicular location and navigation operations in the region"

Click here to view a paper outlining the development and vision behind the system which was presented at GIS 2001 in Vancouver, on February 22, 2001.

Click here to view a presentation outlining the goals and objectives of the BCACSm - CRD. View a PDF format brochure (325 KB) explaining the system.

Product Details

BCACSm has been designed with open architecture in mind. Great care has been taken to ensure that the selection of the equipment comprising the system, particularly the correction data for both real-time RTK and post-mission surveys, will be useable by all GPS equipment. Correction formats used include:

  • RINEX - Receiver INdependent EXchange format - Standard format supported by all major GPS manufacturers, supports code and carrier phase processing for post-mission corrections.
  • RTCM ver. 3.0 - Real-time standard supports carrier phase corrections at present. It is a standard supported by most manufacturers of RTK ready GPS receivers including single and dual frequency centimetre capable units. RTCM ver. 3.0 is a much more efficient format than ver. 2.3, improving it's performance over wireless links compared with version 2.3.
  • CMR+ - CMR is an open standard supported by most manufacturers of RTK GPS rovers.

Accuracy

The best achievable accuracies are approximately:

  • RTK static - 0.010 m (rms)
  • RTK rapid static - 0.030 m (rms)
  • RTK kinematic - 0.040 m (rms)
  • Code differential - 0.5 m (rms)
Vertical accuracies are approximately 2x horizontal.

Achievable accuracy is dependent on a number of factors, including:

  • the quality of the GPS receiver,
  • distance from the base station,
  • GPS constellation geometry during the observation period
  • conditions at the rover site
  • quality of the NAD83 horizontal and CVD28 vertical datum and geoid model in the region.

An integral part of the BCACS is the establishment of a high precision geodetic control network (HPN). The HPN provides a solid datum for GPS operations, providing consistency in coordinates throughout the region covered. The HPN comprises a sparse network of control monuments (2 - 3 km spacing) which are very accurately surveyed within the Provincial, National and International datums. The HPN provides compatibility between RTK GPS operations and conventional survey methods (i.e. total stations and spirit levels).

System Configuration

Real-time

A dual frequency GPS receiver will be installed at each base station. Proprietary software controls the receiver operation, data logging parameters, and real-time broadcast. This component will broadcast the real-time corrections and also log post-mission correction data which can be downloaded from CRGB's BC ACS web site. Radio modems to transmit the real-time corrections from the base stations to the radio repeaters are located at Mount Douglas, Mount Newton and Mount Helmken. Radio repeaters at those three sites will retransmit the RTK/RTCM corrections over the area of the CRD. Users employ portable receivers to receive the corrections directly from the radio modems at the ACPs or through the repeaters. RTK corrections via cellular are also available.

Post-Mission

The GPS receivers will simultaneously log dual frequency data for post-mission correction use. The data is sent, hourly, to the BC ACS Processing Master Active Control Station (PMACS) where it is processed and stored for subsequent download. The data is accessible via the internet through CRGB's FTP Service.

High Precision Network

The completion of this project is the implementation of a High Precision Network (HPN) integrated into the Provincial geospatial reference and the national system (CRD HPN).

High Precision Network

The HPN will provide an accurate three-dimensional geospatial reference throughout the CRD. The HPN comprises approximately 130 monuments placed on a 2km grid in the urban and semi-rural areas of the CRD and a 10km grid (future) in the rural and remote areas. Of course, there are the two Active Control Points providing the real-time and post-mission corrections for the service.

The general requirements for this component are:

  • Precise GPS data collection to obtain precise horizontal and ellipsoidal heights on the monuments and the two Active Control Points. The HPN coordinates will be referenced to surrounding CACS/WCDA base stations.
  • Precise (First-Order) Spirit Levelling from nearby Federal and Provincial bench-marks to establish accurate elevations on the control monuments and ACPs.
  • Precise geoid modelling in support of high accuracy vertical (orthometric, or MSL elevation) positioning within the BC ACSm - CRD.
The HPN will ensure that the geospatial reference will be compatible for all users and all applications within the CRD area.

Click on the image above to view the HPN grid points established for the BC ACSm - CRD in the autumn of 1999. You can also view the 10 km grid stations and the 2 km grid stations.

CRD BC ACSm Radio Coverage Area

The map below shows the RTK GPS coverage area, that is, the areas where centimetre level accuracy can be achieved. (click on the map for a detailed image).

radio coverage area

There is a limit to the distance (approximately 20 km) that a rover can be located from the base stations and "resolve the ambiguities" to the centimetre level. Ambiguity resolution is the determination of the number of complete wavelengths of the GPS signal between the satellite and the GPS receiver. If the ambiguities can not be resolved the result is a "Float Solution", which is an order of magnitude less accurate.

The coverage area for RTK is within approximately 15 - 20 km of the two base stations. Beyond that, an RTK float solution (i.e. < 0.5 metre) or RTCM code solution (i.e. ±1 metre) is available for the entire radio coverage area as outlined with the magenta line. The 15 km RTK coverage radius was confirmed from independent tests undertaken by CRGB in the spring of 1998. It is expected that new developments by GPS manufacturers will allow RTK level accuracies to be achieved at increasing distances from the base stations.

Specifications

For further information on BCACS Municipal (BCACSm) specifications please refer to our Geospatial Reference Standards and Specifications.

Frequently Asked Questions

Refer to the Geospatial Reference Frequently Asked Questions (FAQ) page.

Requirements

There are a number of items required to use the BCACSm.

  • GPS Receiver - The user is responsible for acquiring a suitable GPS receiver and obtaining training from their preferred source prior to applying for an account. It is expected that the client will have reasonable familiarity with equipment and understanding of how to configure it for RTK/DGPS operation. A list of validated GPS receivers can be found below. If the user wishes to obtain equipment not on this list, CRGB should be notified in advance so testing and validation can be discussed and arranged.
  • Handset - The user will obtain a handset from their cellular provider before applying for an account. The cellular provider should be made aware that the intended use of the handset is for the CRD Real-Time GPS Service when it is ordered. A list of validated handsets can be found below.
  • Training - The customer is responsible for obtaining training in the operation of their GPS equipment.

Product Resources

Related Links

Capital Regional District Website (CRD)

How to Buy

Real-time Data

To access the BCACSm–CRD real-time corrections; please contact Peter Breen at the Capital Regional District (tel: (250) 360-3049)
email: pbreen@crd.bc.ca).

Subscribe

Subscriptions for BCACSm–CRD Post-mission Data are available for purchase at our Base Map Online Store (BMOS).

Before Using the Base Map Online Store

Please review the following introductory materials before proceeding to the BMOS site:

Requirements to Use the BMOS >> Product Brochure  >> Currency, Costs, Taxes  >> Product Delivery Times  >> Cancellations, Refunds, Discounts  >>

Pricing

Real-time Data Please contact the CRD
A1 Basic subscription (1 office) $1200 per year
A2 Basic Plus subscription (5 offices) $3000 per year

Program Area

The Geospatial Reference Unit (GSR) defines and manages, according to established standards and professional practices, the spatial coordinate system in the province to support geographic positioning activities.

Copyright

All Crown Registry and Geographic Base information products are protected by Province of British Columbia Crown Copyright. Read more >>