Tracker 2017 Automatica

[Nazarena Lugg]

Wehave a surface that slopes 1.6 to the north. Single-axis trackers with a north-south axis should be installed on this surface. The arrangement of the trackers has a misalign. To map the field we use several tracker arrays. To align the trackers in the correct height we have defined a ground object that gets a tilt of -1.6. We align the height of the trackers with Set auto. altitude. We now have some trackers in the field that are optically lower than the others, although mathematically the height in the coordinates was calculated correctly by PVSyst. Can someone help here?

Hi, after reviewing the scene, I have a better view of the situation.

Basically, the auto-altitude tool is not working as you think it does. At the moment it is not possible to have an array of trackers that has trackers with different altitudes.

What I mean is that because of the misalign, your array has trackers that are more or less distributed along the NS axis. In your case, you want the northernmost trackers to be lower in altitude than the southernmost, in order to follow the slope. However this is not what is happening in PVsyst, which has all trackers stay at the same altitude. For example for the array in red:

For @Michele Oliosi, any possibility to have this be implemented in PVsyst such that NS slope is modified? That is, placing the trackers orthogonal to the surface using whatever reference point is selected.

Instead of using trackers from the beginning, fill the areas with fixed tilt arrays of the same size of the trackers and use an azimuth that gives you the same shape of the trackers (SN axis -> 90 degrees azimuth for fixed tilt) and tilt equal to the max tilt of the trackers.

The automatic identification system (AIS) is an automatic tracking system that uses transceivers on ships and is used by vessel traffic services (VTS). When satellites are used to receive AIS signatures, the term Satellite-AIS (S-AIS) is used. AIS information supplements marine radar, which continues to be the primary method of collision avoidance for water transport.[citation needed] Although technically and operationally distinct, the ADS-B system is analogous to AIS and performs a similar function for aircraft.

Information provided by AIS equipment, such as unique identification, position, course, and speed, can be displayed on a screen or an electronic chart display and information system (ECDIS). AIS is intended to assist a vessel's watchstanding officers and allow maritime authorities to track and monitor vessel movements. AIS integrates a standardized VHF transceiver with a positioning system such as a Global Positioning System receiver, with other electronic navigation sensors, such as a gyrocompass or rate of turn indicator. Vessels fitted with AIS transceivers can be tracked by AIS base stations located along coastlines or, when out of range of terrestrial networks, through a growing number of satellites that are fitted with special AIS receivers which are capable of deconflicting a large number of signatures.

The International Maritime Organization's International Convention for the Safety of Life at Sea requires AIS to be fitted aboard international voyaging ships with 300 or more gross tonnage (GT), and all passenger ships regardless of size.[1] For a variety of reasons, ships can turn off their AIS transceivers.[2]

If a suitable chartplotter is not available, local area AIS transceiver signals may be viewed via a computer using one of several computer applications such as ShipPlotter, GNU AIS or OpenCPN. These demodulate the signal from a modified marine VHF radiotelephone tuned to the AIS frequencies and convert into a digital format that the computer can read and display on a monitor; this data may then be shared via a local or wide area network but will still be limited to the collective range of the radio receivers used in the network.[3]Because computer AIS monitoring applications and normal VHF radio transceivers do not possess AIS transceivers, they may be used by shore-based facilities that have no need to transmit or as an inexpensive alternative to a dedicated AIS device for smaller vessels to view local traffic but, of course, the user will remain unseen by other traffic on the network.

A secondary, unplanned and emerging use for AIS data is to make it viewable publicly, on the internet, without the need for an AIS receiver. Global AIS transceiver data collected from both satellite and internet-connected shore-based stations are aggregated and made available on the internet through a number of service providers. Data aggregated this way can be viewed on any internet-capable device to provide near global, real-time position data from anywhere in the world. Typical data includes vessel name, details, location, speed and heading on a map, is searchable, has potentially unlimited, global range and the history is archived. Most of this data is free of charge but satellite data and special services such as searching the archives are usually supplied at a cost. The data is a read-only view and the users will not be seen on the AIS network itself.Shore-based AIS receivers contributing to the internet are mostly run by a large number of volunteers.[4] AIS mobile apps are also readily available for use with Android, Windows and iOS devices. See External links below for a list of internet-based AIS service providers. Ship owners and cargo dispatchers use these services to find and track vessels and their cargoes while marine enthusiasts may add to their photograph collections.[5]

At the simplest level, AIS operates between pairs of radio transceivers, one of which is always on a vessel. The other may be on a vessel, on-shore (terrestrial), or on a satellite. Respectively, these represent ship to ship, ship to shore, and ship to satellite operation and follow in that order.

The 2002 IMO SOLAS Agreement included a mandate that required most vessels over 300GT on international voyages to fit a Class A type AIS transceiver. This was the first mandate for the use of AIS equipment and affected approximately 100,000 vessels.

In 2006, the AIS standards committee published the Class B type AIS transceiver specification, designed to enable a simpler and lower-cost AIS device. Low-cost Class B transceivers became available in the same year triggering mandate adoptions by numerous countries and making large-scale installation of AIS devices on vessels of all sizes commercially viable. [citation needed]

Since 2006, the AIS technical standard committees have continued to evolve the AIS standard and product types to cover a wide range of applications from the largest vessel to small fishing vessels and life boats. In parallel, governments and authorities have instigated projects to fit varying classes of vessels with an AIS device to improve safety and security. Most mandates are focused on commercial vessels, with leisure vessels selectively choosing to fit. In 2010 most commercial vessels operating on the European Inland Waterways were required to fit an Inland waterway certified Class A, all EU fishing boats over 15m must have a Class A by May 2014,[6] and the US has a long-pending extension to their existing AIS fit rules which is expected to come into force during 2013. It is estimated that as of 2012, some 250,000 vessels have fitted an AIS transceiver of some type, with a further 1 million required to do so in the near future and even larger projects under consideration. [citation needed]1

AIS was developed in the 1990s as a high intensity, short-range identification and tracking network. Shipboard and land-based AIS transceivers have a horizontal range that is highly variable, but typically only up to about 74 kilometres (46 mi). Approximate line-of-sight propagation limitations mean that terrestrial AIS (T-AIS) is lost beyond coastal waters.[7] In addition to port and maritime authority operated transceivers, there is large network of privately owned ones as well.

In the 1990s AIS was not anticipated to be detectable from space. Nevertheless, since 2005, various entities have been experimenting with detecting AIS transmissions using satellite-based receivers and, since 2008, companies such as L3Harris, exactEarth, ORBCOMM, Spacequest, Spire and also government programs have deployed AIS receivers on satellites. The time-division multiple access (TDMA) radio access scheme used by the AIS system creates significant technical issues for the reliable reception of AIS messages from all types of transceivers: Class A, Class B, Identifier, AtoN and SART. However, the industry is seeking to address these issues through the development of new technologies and over the coming years the current restriction of satellite AIS systems to Class A messages is likely to dramatically improve with the addition of Class B and Identifier messages.

The fundamental challenge for AIS satellite operators is the ability to receive very large numbers of AIS messages simultaneously from a satellite's large reception footprint. There is an inherent issue within the AIS standard; the TDMA radio access scheme defined in the AIS standard creates 4,500 available time-slots in each minute but this can be easily overwhelmed by the large satellite reception footprints and the increasing numbers of AIS transceivers, resulting in message collisions, which the satellite receiver cannot process. Companies such as exactEarth are developing new technologies such as ABSEA, that will be embedded within terrestrial and satellite-based transceivers, which will assist the reliable detection of Class B messages from space without affecting the performance of terrestrial AIS.

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