APOGEO: an innovative procedure developed by TIM Italia for improving the network quality
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  Apogeo kit instruments |
Undoubtedly the strongpoint of the kit is the topographic instrument, the technical characteristics of which distinguish it from those of other companies. Such characteristics include precision distance (3mm) and angle (2”) measurements, a reflectorless range (>150 m), and maximum laser divergence of 100 m (1.5mm x 3mm). In particular, the maximum laser divergence is very important for distinguishing two points very close together when measuring across long distances. The use of the PCMCIA card both inside the GPS receiver and the topographic instrument is also a highly useful form of support for customizing other potential functions (for example: direct calculation of the tilt and the azimuth).
In order to increase the accuracy of the business data bases on which all the activities related to the design, construction, maintenance, and optimization of the network are based, the APOGEO (Antennas Procedures On Geographic Enhanced Orientation) operating procedure was developed and patented by TIM both in Italy and abroad. This procedure defines the operating methods for the accurate measurement of geographic coordinates (latitude, longitude, and altitude), orientation with respect to geographic north (Azimuth), inclination with respect to the vertical (Tilt) and altitude from the ground of radio station antennas using the above-mentioned professional instrumentation. The APOGEO procedure has become an integral part of the technical testing standards and contracts with supply and installation companies that operate for TIM. In this way, TIM accepts the facilities only when their conformity to the design specifications has been verified by applying this procedure. The use of the following instrumentation and, subsequently, the APOGEO procedure is intended to promote:
· increased accuracy in the installation, maintenance, and optimization processes by the companies that operate for TIM, through the verification of the conformity of equipment to project specifications. With these instruments, errors that could occur with the use of conventional instruments normally employed by installers of mobile telephone systems (inclinometers, compasses, altimeters, etc.) are eliminated.
· qualitative improvement of the network in terms of coverage and protection from interference, thanks to increased precision in the calibrating of antenna tracking. Furthermore, given the greater sophistication of future UMTS systems, this will be an increasingly important consideration.
- greater reliability of the business databases necessary for the design of the network, for the supply of added-value services (eg. services based on localization), and for the processing of impact area data necessary in order to conform to the electrosmog regulations now in force.
- performing necessary remote verification of the antennas, while guaranteeing the safety of personnel (TIM or suppliers') directly involved in the actual surveying activities.
In general, each radiomobile installation irradiates the signal from multiple cells (directions) installed on a towering structure (pylon, pole, building) by means of appropriate supports. Each cell is made up of multiple antennas (fixed electromagnetic sources) the support structures of which may vary from one installation to another. The element to which all topographic survey operations required by the APOGEO procedure therefore refer is a single antenna.
 TIM antenna site |
The identification of the geographic coordinates (latitude, longitude, and altitude) of the antennas in the WGS84 system and of their tracking angle on the horizontal plane (azimuth), with respect to geographic north, generally requires the completion of a mixed survey based on simultaneous GPS instrumental surveys and topographic surveys. In fact, bearing in mind that the points to be surveyed are inaccessible, it becomes necessary to record two or more reciprocally visible points in the vicinity of the antennas by means of GPS, from which the points on the antennas are visible, and as such detectable by a topographic instrument, which is in turn capable of recording angular measurements (azimuth directions and zenith angles) as well as distance.
The position of GPS vertices in relation to points on the antenna to be measured must planimetrically define triangles, preferably equilateral triangles, in order to optimize planimetric precision.
For the coordinates (determined in WGS84), the point at the base of the antenna is measured, while the two points on the same horizontal plane are measured for the azimuth.
    Coordinates and azimuth measurement |
The calculation of the antenna tracking angles of the on the vertical plane (tilt) and the height of the antenna from the ground may be performed by using the topographic instrument only, positioned on opportune vertices (not GPS), from which the points to be measured are visible. More specifically, the calculation of height in relation to the ground is performed by determining the difference based on the measurements of the incline distance and the zenith angle. Calculation of the tracking angle on the vertical plane (tilt) is instead always determined by measuring the azimuth directions, the zenith angles, and the distances to both the identified points, lying on the same vertical.
  Antenna tilt and height measurement |
It is important to emphasize that a higher or lower level of complexity in performing an on-site survey, even with equal antenna dimensions, is strictly related to local logistic limitations . It is obvious that a survey of a radio station in the suburbs with each antenna installed on the same pylon is much quicker and easier than that of a radio station in an urban area on the roof of a building with each antenna on its own pole. It is therefore always necessary to adapt such procedures to the specific conditions of each individual site.
THE GEOTIM NETWORK
TIM Italia has built a GPS network throughout Italy, able to support professional GPS users with precision positioning for various applications and in numerous market segments. As well as providing a DGPS differential correction over a mobile telephone network, TIM's network is used to optimise the use of its antennas and is able to monitor the network for radio frequency leakages, supporting scientific documentation regarding the extent and disposition radio frequency electromagnetic fields – an important issue with health and environmental implications.
In Italy, the implementation of the law regarding the definition of radio frequency electromagnetic field limits that are compatible with human health, represents an opportunity for TIM to strategically adopt a network infrastructure and suitable tools for the correct georeferencing of mobile telephony installations and subsequent punctual monitoring of areas of impact of radio frequency electromagnetic fields.
This resulted in the need for a project aimed at the realization of a network of GPS reference stations (which currently number 34), called GeoTIM, the first of its kind among mobile telephony operators in Italy. By means of this network, TIM has developed an instrument that is essential for meeting institutional requirements (Local Health Care Services, Regional Agencies for Prevention and the Environment, Ministry of Communications, and other public administration agencies), in that it provides scientific documentation regarding the extent and disposition of volumes in reference to their own radio stations, as well as the distances between these same stations and public buildings (schools, hospitals, etc.).
During its construction, in addition to acquiring know-how in an uncommonly large sector for a mobile telephony operator, the company began to realize the inherent value of the resource at hand, which could focus its interest on what is now a mature market. The availability of a GPS network for precision positioning, an essential form of support for performance optimization in various market sectors, such as GIS mapping, topographic and cadastral surveys, technological network management, the management of natural and environmental resources, intelligent transport, precision navigation, etc.
 Distribution of the GeoTIM network |
The strong points of the GeoTIM network can be summarized as follows:
· Uniform distribution over the entire national territory: The fact that TIM has a considerable number of radio stations distributed throughout the territory (urban, interurban, rural, mountainous regions) has simplified the identification of sites suitable for the installation of a permanent GPS station (maximum visibility, absence of interference, structural stability, etc.), which has rendered GeoTIM the only network with uniform national coverage.
· organization within the IGM95 national geodetic network:
· ASI (Italian Space Agency) certification: certain GeoTIM stations will become part of a group of stations managed by ASI within the EUREF; ASI will issue a weekly data certification for the differential correction produced by the GeoTIM network, therefore offering national and international significance and credibility, even in scientific circles.
· easy network interconnection: GPS data travels within an intranet business network (equipped with a high-capacity backbone and an elevated number of POP addresses), which allows for the integration of individual GPS stations and the creation of a truly integrated GPS network. A management platform for the entire system (LMP) allows for the concentration of data within a single collection center, which also functions as the customer's service access point.
· Network-monitoring system: GeoTIM monitoring is managed in a similar manner to other TIM network infrastructures.
· reliability of service and timely maintenance interventions: TIM's presence within the territory and their on-site intervention capacity allows for the optimization of station restore times, guaranteeing high service reliability.
· ability to supply data in standard RINEX and RTCM formats, respectively, for differential correction in Post Processing and in Real Time.
· implementation: from a technical point of view, the GeoTIM network is easily expandable where necessary .
The reference stations currently consist of a GPS geodetic, double frequency, 12 channel L1/L2, C/A and P code, RTCM and RTK receiver and a local server that manages the station itself and interfaces with the business intranet network, both for connection to the management platform for the entire system (LMP) as well as to the alarm monitoring system.
The antenna is a choke-ring type. This guarantees phase center stability, effective multipath protection, and also ensures the possibility of tracing satellites even at low-level elevations.
THE GEODATA SERVICE
The TIM GeoData service, which was conceived with the aim of making GeoTIM network data available to external clientele, was commercially launched in September 2002. The availability of a national infrastructure for precision positioning allows for the expansion of new market segments in multiple sectors. As already mentioned , GPS differential correction data is available according to the two classic access modes already used by professionals with differential GPS instrumentation, post-processing and real-time.
POST PROCESSING SERVICE
The GPS stations periodically send time files containing data for differential correction, formatted according to the RINEX (Receiver Independent Exchange format) international standard.
 Architecture of the GeoData in Post Processing Service |
The GeoData Post Processing service assumes that the customer carries out his GPS survey with a rover unit, which records the measuring session. Subsequently, he connects to the www.business.tim.it web site from his Internet station. Following the login phase (insertion of the User-ID and Password), he will access a page from which he can:
- select the desired GPS station;
- select the data sampling frequency (1, 5, 15 or 30 seconds)
- insert the desired date and time slot
  selection of the desired GPS station selection of the frequency, date, and time slot |
In response to the query, the LMP supplies a list of existing files (maximum 30-days old ), the possibility of downloading those required and, through the use of specific software, post-processing of the field measurements to refine the accuracy of results.
 Time files available for customer download |
REAL TIME SERVICE
The GPS stations continually transmit differential correction data to the LMP, in accordance with the RTCM SC-104 (Radio Technical Commission on Maritime Communication, Special Committee 104) international protocol standard, Release 2.2.
 GeoData Real Time Service Architecture |
The GeoData Real Time service calls for the customer to activate a telephone connection with the LMP by dialing a TIM radiomobile number for the desired GPS station, from a GSM mobile phone (with active SIM card), that is connected to a GPS rover receiver.
When the connection is made, it starts the GPS measurement session and continually receives the requested data at a speed of 9.6 Kbits/s, performing differential correction directly on the field and obtaining highly accurate data.
The GeoTIM network constitutes a first homogeneous and certified national system nucleus for georeferencing. The related GeoData service allows customers to use the network across the entire national territory.
 Ottavio Colangelo |
 Massimo Falchi |
 Roberto Balducci |
 Sergio Corradini |