Mobile Surveying Solutions 1

Microwave links, satellite communication antennas, mobile phone transmitter stations, radio masts in addition to optical fibre networks are all part of the network of telecommunications assets, which permit even remote farming communities to talk to people in other cities in other countries. All of the different telecommunications assets are positioned by surveyors. In addition to site plans, access plans, lease areas and height information, attribute data such as building types and technology aspects is collected.

Accuracy requirements for the various surveys differ. Over 200 leases for the telecommunications sites are registered per year which mostly require centimetre accuracy. Dual frequency GPS receivers and total stations are used. GPS and total stations provide positions which are ultimately transformed onto ISG, the NSW adaptation of the Australian Map Grid (AMG). Telstra’s CAD system, CADDSMAN, stores positions simultaneously in both ISG and AMG providing planning information readily for state or national purposes.

Many homesteads in the more remote areas of NSW rely on radio for communications. Radio provides a cost effective alternative to cabling. There are over 3000 radio subscribers throughout NSW. Presently about 1600 radio customer masts have been coordinated. Positioning of the customer radio masts are made by private survey firms under contract to Telstra. Differential GPS (DGPS) systems are used to collect the position to around 1-2 meter accuracy. Simultaneously, customer data including name, address and phone number are verified and ultimately stored as attribute data with the radio mast position in Telstra’s GIS. Regardless of the type of DGPS unit used by the contract surveyors, the attribute data is required in a Microsoft ACCESS format defined by Telstra which is then linked to MAPINFO GIS. The ACCESS database has a number of tables including information on the site, the customer, the transmitter structure and other telecommunications equipment.

Whilst Leica GPS System 300 is routinely used for survey control work around the various sites, it has also been used in kinematic mode to establish access routes and contour plans. By mounting a GPS antenna over the front of a 4 wheel drive vehicle and adopting an average height above the ground, GPS measurements were recorded at set time intervals and post processed to map both the centreline of access trails and spot heights around hilltop locations. The vehicle drove in a spiral to the top of the hill and the post processed kinematic GPS positions were ported from Leica SKI through to Leica LISCAD Plus surveying software where both the access trail’s centerline and the hilltop contours are plotted and stored. Access trail widths are determined from the GPS centerline and become "access areas" for right of access to the site. From the contour plans, Telstra’s planners design optimum heights for the transmitter masts together with guy line positions to support the masts. Lease areas for the transmitter sites are kept to a minimum but must wholly enclose the guy anchor pins. The final set out survey of the guy anchor pins proved that the creative approach to using kinematic GPS for contouring was not only fast but reliable. Set out heights for the anchor pins were on average within 0.1 of a meter of the natural surface, requiring only minimal adjustment.

Easy flow of data gives productivity

Of key importance to the whole flow of data from the transmitter sites into the GIS database is the simplicity of data transfer. The GPS System 300 and the TC1100 total stations are equipped with PCMCIA cards which easily insert into laptop or PC drives. Both SKI GPS processing software and LISCAD Plus surveying software conveniently access the data formats on the PCMCIA cards and rapidly process the data into files of relevant positioning data for passing onto Telstra’s CAD package for map and plan production or to Telstra’s GIS for analysis and planning. Standardising on one GPS, total station and surveying software system ensures minimum interrupts to the flow of data through the various systems. In addition, one organisation supports the overall surveying hardware and software solution which only adds to operating ease.

Often the simplest pieces of data build into a significant asset when finally deployed into an enterprise wide system. For instance, a critical aspect of the "as built" survey of the sites is to now measure the heights of the transmitter aerials. The Leica TC1100 includes an on-board software program to determine the height of a remote object such as the transmitter mast and is often deployed to record the transmitter height with all other site information on the PCMCIA card. Ultimately that height data may be recalled by a planner using the GIS to define effective radio route propagation. Just another step to developing and maintaining telecommunications infrastructure at peak performance.

Additionally, the surveyors often use the alphanumeric keys on the total stations to record notes about the surveying procedures and about the sites. These notes become part of the original electronic data records thus providing accurate confirmation of field books and other reports and enabling electronic storage of all data associated with the survey.