rapporter.ffi.no
Contents
1. 42 1 The init file The contents of the init file must be in the same order as they are in the examples This section will not describe the entire file since the files included with the examples are heavily commented 4 2 2 Data storage The first section describes where AISDET shall look for vessel traffic models antenna patterns and required input files Lines that start with a are treated as comments PATHS Vessel data C Program Files x86 AISDET share aisdet vessel_data Antennas C Program Files x86 AISDET share aisdet antennas Input files C Program Files x86 AISDET share aisdet input files 14 FFl rapport 2011 02300 4 2 2 1 Orbit The second section tells AISDET to load an ephemeris file The orbit file contains the ephemeris and required epochs ORBIT Ephemeris satellitell orb 4 2 2 2 Vessel list The vessel list files contain for each vessel latitude longitude distance km to nearest coastline messages per minute and nominal transmission interval in slots The software comes with several vessel distributions for class A and class B equipped vessels AISDET assumes that class B vessels transmit at 2W Load vessel data VESSELS CLASS A Vessel file vessel list espais2014 1list VESSELS CLASS B Vessel file none Some suggestions for third and fourth frequencies require that only vessels without access to any land based base station shoul2. FFl rapport 2011 02300 15 Setting the output file to something different than none tells aisdet to write a SOTDMA file with the given name Both values can be set to none SOTDMA SOTDMA file none Output file satellitell sotdma In order to run both examples it is therefore necessary to first execute amp C Program Files x86 AISDET bin aisdet exe h_win init 86400 in CATemp examples dipoles INX CA Temp examples dipoles 12 X CA Temp examples patch_arrays I Npatch 07 0 00 0 PX and The other simulations can be started as soon at the SOTDMA files have been generated These simulations will load the relevant SOTDMA and coverage files 4 2 2 4 Selecting an antenna AISDET can load three different types of numerical antenna patterns in addition to several ideal antenna patterns The first valid numerical antenna pattern is a slightly modified NEC Win output NOU file These files require an additional header and one line consisting of dashes only Examples of valid files can be found in the data directory of your AISDET installation The second type of numerical antenna patterns are files produced by Thales Alenia Space TAS as a part of 2 These files can contain circular or linear polarized patterns see The linear polarized patterns do not contain all the necessary information about the polarization This is the reason for the third argument to AISDET The final type of numerical antenn
3. Temp examples dipoles nap_update_interval dat 1 1 This will generate a figure that you have to save manually It might be a good idea to edit the color map before the figure is saved since the color maps defaults to a maximum value of 24 hours Figure 4 7 illustrates such a map after setting the maximum value in the color map to 6 hours 24 FFl rapport 2011 02300 N w A Ou 1 D Figure 4 7 Required time to get updates from 80 of the vessel Dark red implies an update interval of six hours or more This map ignores the times when an area can not been seen due the two satellites coverage 4 4 6 Distribution of update intervals aiscnt_dist can also generate distributions of update intervals within selected target areas A set of scripts included with the examples simplifies this process Linux cd HOME tmp examples dipoles sh aiscnt_dist sh Windows cd C Temp examples dipoles aiscnt_dist PS1 The output will be a large set of text files and four figures for each target area Both of these scripts require that gnuplot is installed and in the system s path variable The first figure gives the fraction of vessels inside a target area that the users can expect to receive updates from within a given time interval assuming a set of ground stations Figure 4 8 is an example of such a figure It also includes curves for vessels with specific repetition intervals and for vessels on open seas This figure is bas
4. create both single hour detection probability maps and accumulated detection probability maps The script will redo the same process on hours 2 through 7 and so on until the end of the simulations Hence DELTA can be interpreted as the length of a moving window where the scripts create detection probability maps The commands are cd C Temp examples dipoles remap_hours PS1 remap_hours_constellation PS1 22 FFI rapport 2011 02300 4 4 3 2 Hourly remap files on Linux cd HOME mp examples sh remap_ hours sh sh remap_ hours_constellation sh 4 4 4 Table of detection probabilities in target areas aiscnt is a program that counts the number of vessels within a target area and how many of those vessels that were detected within a user selected interval The following commands will generate a simple table of detection probabilities Linux cd HOME tmp examples sh aiscnt sh Windows cd C Temp examples dipoles N aisent PS1 4 4 5 Global map of update intervals The purpose of this section is to produce a global map that show how much time it takes to receive updates from 80 of the vessels It requires access times for each satellite to a set of user selected ground stations These access times can be generated using the program access that is included with the Heliosat package To see a simple user manual execute amp C Program Files x86 Heliosat bin access exe h access requires ground stations l
5. done at FFI or unless it is required by projects that FFI participates in References 1 ystein Olsen ESPAIS AIS System Study Maritime Traffic Characterization 2010 2 ystein Olsen ESPAIS AIS System Study Payload Performance Analysis Report 2010 FFI rapport 2011 02300 31
6. they are sent to the server This can be achieved by running the simulation over a short time in Windows PowerShell amp C Program Files x86 AISDET bin aisdet exe h_win init 100 4 2 4 Using atd Linux The shell scripts batch partl jobs and batch part2 jobs use atd to achieve the same service on Linux as the AIDET server on Windows 4 3 Modifying the receiver performance The best way to modify the receiver performance is to edit the location of the input files in the configuration file for AISDET and the copy the original contents to the new location There are three sets of files that can be edited The file filter txt contains the filter characteristics for the receiver Its first column gives the relative frequency offset in KHz for messages arriving at the same time while its second column gives discrimination in dB Hence this file tells AISDET how to correct the received signal strength of a colliding message with a given frequency offset to the message its attempting to decode The number of frequency steps is not important but it must be in increasing order It is also possible to change the performance of the SIC algorithm if SIC is set in the AISDET configuration file The performance of the algorithm is defined in the file sic txr Its first column gives D U i e signal strength of the desired signal to the undesired signal s The second column set how much of the desired signal that can be removed if the
7. FFl rapport 2011 02300 AISDET 2 0 User manual ystein Olsen Norwegian Defence Research Establishment FFI 7 December 2011 FFI rapport 2011 02300 121002 P ISBN 978 82 464 2012 7 E ISBN 978 82 464 2013 4 Keywords AISDET Simulering AIS Satellitt Approved by Richard B Olsen Project Manager Johnny Bardal Director 2 FFl rapport 2011 02300 English summary This document is the user manual for AISDET v2 0 which a software collection that simulates the performance of space born AIS receivers It models worldwide traffic conditions and calculates the received signal taking into account media effects antenna gains receiver performance satellite orbits and variation in the transmitted signal characteristics AISDET is developed solely by ystein Olsen at FFI The development started during the development of the AISSat 1 satellite during the FFI project 1104 INNOSAT II and continued during 1210 INNOSAT IH Some adjustments have been done to produce analyses for various ESA studies and bilateral projects with French industry FFI rapport 2011 02300 3 Sammendrag Dette dokumentet er brukermanualen for AISDET v2 0 som er en samling av programvare som simulerer ytelsen til rombaserte AIS mottakere Programvaren modellerer global skipstrafikk og tar hensyn til media antenne gain mottakerens ytelse satellittbaner og endringer i egenskapene til det utsendte signalet AISDET er utviklet av ystein Olsen v
8. Linux the corresponding commands are HOME bin odesolver h cd HOME tmp examples dipoles 1 I sh run_odesolver sh mv heliosat orb satellite I l orb FFI rapport 2011 02300 13 cd HOME tmp examples dipoles 12 sh run_odesolver sh mv heliosat orb satellitel2 orb cd HOME tmp examples patch_arrays 11 sh run_odesolver sh mv heliosat orb satellitel l orb cd HOME tmp examples patch_arrays 12 sh run_odesolver sh mv heliosat orb satellitel2 orb 4 2 Running the simulations The aisdet program is an end to end simulation tool for reception of AIS messages in space Running the program without any arguments will write a simple user manual to the console C Program Files x86 AISDET bin aisdet exe This program takes from one to three arguments The first argument is a text file that acts as a configuration file Only an overview of this file will be given in this section since the configuration files included with the examples contain their own documentation The second argument determines how long to run a simulation The last argument is used to set the polarization of specific antenna patterns see section 4 2 2 4 It is necessary to create sub folders for each AIS antenna since each antenna pattern requires one simulation For example C Temp examples dipoles I1 has X Y and Z folders for three different antennas with one configuration file in each folder The examples can be run without any modifications
9. SDET developed at FFI The software package comes as a self extracting archive on both Windows and Linux The post processing steps require PowerShell on Windows A small subset of an additional software package Heliosat is distributed along with AISDET This package includes a few programs to propagate orbits and compute accesses to ground stations and target areas These programs are not parallelized to utilize multiple processors but most tasks will require multiple simulations that can be run in parallel The document describes how to efficiently set up multiple simulations Each simulation will require up to several hundred MB of RAM A fast hard drive is strongly recommended for the post processing steps 2 Simulation tool AISDET is a software collection developed at FFI to analyze the performance of satellite based AIS systems Its core program is called aisdet which uses global vessel maps to simulate reception of AIS messages at Low Earth Orbit LEO Each vessel transmits according to the SOTDMA scheme on two channels and AISDET computes the signal strength of each message at the receiver to check if it can be decoded or not This decision is made by either defining a signal to noise level for a 20 package error rate or by using lookup tables that give the receiver performance 2 1 Modeling Each vessel transmits according to the SOTDMA protocol This requires a nominal repetition interval for each vessel and knowing which ves
10. a pattern requires two filenames on the antenna diagram line in the init file The first file must contain the theta direction of the polarization and the second file must contain the phi direction See for example AIS TET 3mon PI abs Dir Theta csv and AIS TET 3mon PI abs Dir Phi csv C Program Files x86 AISDET data antennas 16 FFI rapport 2011 02300 4 2 2 5 Receiver performance There are five different options to define the receiver s performance The first method simply sets D U ratio in dB at a 20 package error rate From this AISDET will estimate the bit error rates at other D U rations The second method loads the tables that give the performance of the ESA algorithm 2 These tables are located in the perf_detector_ interf txt files under the data folder of the AISDET installation see C Program Files x86 AISDET share aisde input_files on Windows and HOME share aisdet input_files The content of these files can be edited to run simulations with different receiver performances as long as the format stays the same The last three options are similar and define which performance files to load for two and three colliding messages AISDET will use the ESA tables for any other number of colliding messages 4 2 2 6 Other Each simulation expects to find a media file in the work folder It contains two sections The first section describes how to treat the trop
11. cludes a service that automatically distributes simulations over available CPUs and cores It will create and monitor the folder CNAISSimNWserver Any file dropped into this folder will be parsed and each line with a valid description of a simulation will be added to its queue The number of simulations it will run simultaneously depends on the computer s number of cores It will keep track of the queue during reboots of the computer it is installed on How this service can be used is described in section 4 2 3 Installing this service requires Windows Server 2003 Resource Kit Tools This can be installed on Windows XP and newer version of Windows 1 To create the AISDET_server service open a Command Prompt and execute C Program Files x86 Windows Resource Kits Tools instsrv exe AISDET server C Program Files x86 Windows Resource Kits Tools srvany exe 2 Start regedit and locate 10 FFI rapport 2011 02300 HKEY LOCAL_MACHINE SYSTEM CurrentControlSet Services AISDET_server 1 From the Edit menu click New gt Key and rename it to Parameters 2 Select the Parameters key 3 From the Edit menu click New gt String Value rename it to Application and select Modify from the Edit menu Set Value Data to C Program Files x86 AISDET bin aisdet_server exe 4 Close Registry Editor 5 Start the compmgmt msc using Start gt Run Select Service and Applications gt Services locate AISDET_server and start the service as show
12. d the detection probability for orbits up to and including number XXX The data folder of the AISDET installation contains MatLab scripts to plot these maps This folder must be in MatLab s search path and MatLab must have the Mapping Toolbox installed The MatLab command to plot detection probabilities for a single antenna is plotprob_folder C Temp examples dipoles 12 X 0 1 15 0 0 Satellite 12 X antenna orbit 000 This command plots orbit number 1 through 15 and the script contains an explanation of the arguments Figure 4 1 gives an example of a resulting probability map Plotting accumulated detection probability maps is similarly plotprob_folder C Temp examples dipoles 12 X I 1 15 0 0 Satellite 12 X antenna orbit 000 Figure 4 2 shows the accumulated detection probability after 15 orbits for a single antenna Figure 4 1 Detection probability over one orbit for a single antenna FFI rapport 2011 02300 19 Figure 4 2 Detection probability accumulated over 15 orbits 4 4 2 Detection probabilities for each orbit The previous figures show only the results for a single antenna It is possible to combine the results from different antennas and satellites into single maps This requires a set of remap files that can be generated with the help the program called aisdet_remap Section 4 4 2 1 and 4 4 2 2 describes how to generate the necessary files on Windows and Linux The follo
13. d transmit on these frequencies Setting the following value to true removes all C vessels that are less than 40nm from any coast Delete vessels near false 4 2 2 3 Coverage and SOTDMA files This section is only important if the intent is to simulate more than one antenna on a satellite AISDET cannot simulate multiple antennas in a single run but multiple antennas can be achieved by running one simulation for each antenna and combining the results for all antennas in a post processing step This requires that each run uses exactly the same message pool which is the purpose of the SOTDMA files A SOTDMA files contains a list of message transmission times for each vessel and it can be generated as part of a simulation AIDET can also generate coverage files They contain information about when the vessels are visible from the satellite It is always recommended to generate coverage files since they are used in the post processing step and since it will speed up the runs for the other antennas A file that contains the coverage for every vessel Setting the output file to something different than none tells aisdet to write a coverage file with the given name Both values can be set to none COVRGE Coverage file none Output file satellitell cov A predefined file with SOTDMA slots must be loaded when simulating multiple antennas to ensure identical transmissions for each slot
14. ed FFI Utviklingen startet i forbindelse med utvikling av AISSat 1 satellitten under FFI prosjekt 1104 INNOSAT II og er videref rt i l pet av 1210 INNOSAT III Noen tilpasninger er gjort for gjennomf re analyser under forskjellige ESA prosjekter og under bilateralt samarbeid med fransk industri 4 FFl rapport 2011 02300 Contents 2 1 2 2 2 3 3 1 3 1 1 3 1 2 3 1 3 3 2 4 1 4 1 1 4 1 2 4 2 4 2 1 4 2 2 4 2 3 4 2 4 4 2 5 4 2 6 4 3 4 3 1 4 3 2 4 3 3 4 3 4 4 3 5 4 3 6 4 3 7 Introduction Simulation tool Modeling Performance Assessment Method Input Output Data Installation Windows Installing Heliosat Installing AISDET Windows PowerShell Linux End to End performance analysis Propagate orbits Windows Linux Running the simulations The init file Data storage Selecting an antenna Receiver performance Using the AISDET server Windows Using atd Linux Post processing Plotting detection probabilities per antenna Detection probabilities for each orbit Hourly detection probabilities Table of detection probabilities in target areas Global map of update intervals Distribution of update intervals Detection probability in a moving window Summary References FFI rapport 2011 02300 5 oN OD OD o 12 12 12 12 13 13 14 14 14 16 17 17 18 18 19 20 21 23 23 25 29 31 31 1 Introduction This document is the user manual for a software package called AI
15. ed on a common distribution of update intervals for all of the vessels within the target area The plateau at the right end of the figure indicates the detection probability within this target area Figure 4 9 is an example of the second type of figures It gives the distribution of mean update intervals for the vessels within a target area Figure 4 10 and Figure 4 11 correspond to Figure 4 8 and Figure 4 9 but show instead the time it takes to get the data to the users These last two figures are scaled to the fraction of the detected vessels instead of the fraction of all of the vessels within the target area Figures like Figure 4 8 might in some cases show vessels with update intervals close to zero minutes This happens if a FFI rapport 2011 02300 25 vessel is seen by satellites over multiple passes without access to a ground station It is therefore important that the timeliness is shorter than the revisit time of a target area Fraction of vessels CDF 0 50 100 150 200 250 300 350 Update interval minutes Figure 4 8 The fraction of vessels in the North Atlantic that the users can expect to receive updates from within a given time interval assuming ground stations in Cyprus and Madrid 26 FFI rapport 2011 02300 Fraction of vessels 0 50 100 150 200 250 300 350 Mean update interval minutes Figure 4 9 Fraction of vessels as a function of the vessels mean update interval in the North Atlantic assuming ground
16. el or by using receiver performance lookup tables Differences in travel times cause messages to partly overlap which implies a bit error rate that varies during the message The probability of decoding a message is http www cx unibe ch aiub ionosphere html FFl rapport 2011 02300 7 224 P A p 2 1 i 1 pi is the bit specific bit error rate for signal to interference or signal to noise The interference is treated as white noise if there are no suitable look up tables for the receiver performance with one or more interfering sources Each message s detection probability is written to a file This assumes that 224 bits are necessary to successfully decode a message Messages of type 1 which is the most common transmitted message have 168 bits plus an additional 16 bits for CRC check Hence the 224 bits include training sequence start flag etc The performance of the system is determined by either counting the number of ships flagged as detected within target areas or by analyzing files with message probabilities 2 3 Input Output Data Figure 2 2 gives an overview of the inputs to and outputs from the simulation software Required inputs e Orbital elements of the satellites e AIS payload antenna pattern either an ideal pattern or a numerical model e A numerical model should include the effect of the platform on the pattern e Antenna orientation in space nadir pointing antenna or offset from nadir e Ionosp
17. ess_02_groundstations mv cdfu update timeliness 02 groundstations mv cdft update timeliness 02 groundstations Nsummarize update intervals PS1 4 4 7 Detection probability in a moving window The last scripts are used to compute detection probabilities within moving windows The length of the windows and the target areas are set in the script These scripts output text files which contain one line for each time step The first column is the middle of the interval then follows the number of detected vessels the number of vessel inside the target area time latitude and longitude of the last detected vessel and finally the fraction of detected vessels The scripts in the examples give results for a single satellite However it should be trivial to edit the scripts to show results for two satellites Linux cd HOME tmp examples dipoles sh aiscnt intervals sh gnuplot plot interval gp Windows may warn about files that do not exist cd C Temp examples dipoles aisent_intervals PS1 amp C Program Files x86 gnuplot binary gnuplot exe plot interval gp Figure 4 12 shows the output from the above two commands FFI rapport 2011 02300 29 orn of Africa orth Atlantic Detection probability Time hours Figure 4 12 Detection probabilities in different target areas using a three hour moving window 4 5 Post processing without AISDET It is possible to do two of the post processing steps see section 4 4 5 a
18. here map if the antenna is not circular polarized e Receiver performance which can be estimated either from a performance lookup tables or by selecting the required signal to noise for 20 packet error rate The first option must include performance as a function of signal to noise and optionally the performance as a function of the number of interfering messages and the Doppler shifts of the interfering messages The second option uses an approximate function to estimate the bit error rates at other levels o The algorithm may be iterative i e it attempts to remove decoded messages from the received signal to see if other messages can be decoded Locations of ground stations can optionally be used to compute the timeliness of the data and estimated data storage requirements The outputs are e Files that provides the coordinates of the sub satellite point the number of vessels within the field of view the number of detected vessels and statistics of the number of messages per slot every 10 second e Files with the detection probability of each message e Vessel detection probability maps per orbit and accumulated maps e Detection times of each vessel These files can be loaded by Satellite Toolkit STK to create multi track objects 8 FFl rapport 2011 02300 Timeliness of data and storage requirements Orbital elements ST Receiver parameters eee ewww AISDET gt A fo Ve O
19. isted in a text file that has a specific format The examples include ground station files that define two ground stations one in Madrid and the other in Cyprus To compute access times on Linux cd HOME tmp examples dipoles 11 access o Satellite l orb g ground stations stat r satellite l acss cd HOME tmp examples dipoles 12 access o satellitel2 orb g ground stations stat r satellitel2 acss Windows cd C Temp examples dipoles 1 I amp C Program Files x86 Heliosat bin access exe o satellite I I orb g FFI rapport 2011 02300 23 ground_stations stat r satellite l acss cd C Temp examples dipoles 12 amp C Program Files x86 Heliosat bin access exe o satellitel2 orb g ground_stations stat r satellitel2 acss Keep these access files as they will be needed in the next sections too The global map can now be created with help of scripts included with the examples These scripts use the program aiscnt_dist Linux sh aiscnt_map sh Windows Miscnt map PS1 small warning is needed here These scripts and the scripts in the next section add one argument iup to the aiscnt dist list of arguments It causes aiscnt dist to ignore update intervals longer than 256 minutes because of the constellation s coverage This option will have little or no effect on large constellations The resulting files can again be plotted with the help of a MatLab script included with AISDET plotprob_func 1 Dipoles C
20. l 3 2 Linux The Linux version also includes scripts to help running the simulations These scripts assume that Heliosat and AISDET have been installed to the user home directory Installing Heliosat and AISDET therefore amounts to running the following commands from a terminal sh Heliosat 1 0 1 Linux sh prefix HOME sh AISDET 1 0 1 Linux sh prefix HOME It is necessary to accept the license agreement and not include subdirectories This version does not come with a server since atd combined with included scripts performs many of the same tasks atd is included with most Linux distributions and must be configured according to your system specifications 4 End to End performance analysis The first step is to create a catalog structure Each satellite must reside in its own folder and it is strongly recommended to give each folder a name that consists of two digits For a 12 satellite constellation with three satellites in each plane the folder names could be 11 12 13 21 22 23 31 32 33 41 42 and 43 Two examples have been included with the software They can be found in C Program Files x86 AISDET share aisdet examples on Windows and in HOME share aisdet examples on Linux The following walkthrough assumes that the examples folder has been copied to C Temp on Windows and HOME tmp on Linux 4 1 Propagate orbits The first step of any simulation is to propagate an orbit for each satellite in the constellatio
21. message has been successfully decoded The first or the last value will be used if the D U is out of bounds The last files are the perf_detector_ interf txt files which gives the performance for 0 1 2 or 5 colliding messages The first column in these files gives the Signal to Noise Ratio SNR for the received messages The next columns give the Bit Error Rates for different C I values 4 4 Post processing The post processing is done using software included with the Heliosat and AIDET packages All the programs are driven from the command line but some of the programs are nearly impossible to set up manually due to large number of arguments The AISDET installation comes with several scripts that do most of the heavy lifting These scripts can also be found in the folder with the examples and those scripts can be used without any modifications However other simulations might require some editing in a text editor Hopefully the comments in the scripts should be sufficient to understand what the different settings do Only the dipole example will be covered in this section The post processing steps for the patch arrays are for all purposes identical 18 FFI rapport 2011 02300 4 4 1 Plotting detection probabilities per antenna Each simulation produces a set of files named ais_accprob_orbXXX dat and ais_accprob_orbXXX dat These files contain respectively a map of the detection probabilities for orbit number XXX an
22. n The orbit propagator is a console program that must be run once for each satellite It should be run within each satellite folder i e inside 11 12 12 FFl rapport 2011 02300 4 1 1 Windows The propagator is a console program To see its user manual start Windows PowerShell and execute amp C Program Files x86 Heliosat bin odesolver exe h This software is quite complicated to run correctly The examples folder contains for each satellite odesolver bat which simplifies this set The following commands will generate the necessary orbits cd C Temp examples dipoles 1 I run_odesolver bat mv heliosat orb satellite I l orb cd C Temp examples dipoles 12 Nun odesolver bat mv heliosat orb satellite 12 orb cd C Temp examples patch arraysWi I Arun odesolver bat mv heliosat orb satellite I l orb cd C Temp examples patch_arrays 12 Arun odesolver bat mv heliosat orb satellite 12 orb It should be sufficient to edit the epoch start time stop time and the satellite file in the bat script for other scenarios The examples include necessary satellite files and in these files it is sufficient to edit the lines with Orbital elements and initial conditions It is quicker to use tlesolver exe if there are TLEs for each satellite and it too has a user manual available with the h switch odesolver exe is quite slow as it is currently designed to propagate orbits for a month with cm accuracy 4 1 2 Linux On
23. n aisdet_remap exe h All the necessary files can be generated with these commands cd C Temp examples dipoles remap_orbits PS1 remap_orbits_constellation PS1 4 4 2 2 Remap files on Linux The corresponding commands on Linux are HOME bin aisdet remap h cd HOME tmp examples sh remap orbits sh sh remap_orbits_constellation sh 4 4 3 Hourly detection probabilities The previous section showed how to combine the results from different antennas and satellites over specific orbits It is also possible to use aisdet_remap to combine the message probability files with a step size of one hour instead of one orbit Sections 4 4 3 1 and 4 4 3 2 explain how to FFl rapport 2011 02300 21 do this The following two commands correspond to the two MatLab commands in the previous section plotprob_folder C Temp examples dipoles Ui I hours_01_06 0 1 6 1 1 One satellite hour 000 plotprob_folder C Temp examples dipoles hours_01_06 1 1 6 1 1 Both satellites orbit 000 Figure 4 5 Detection probability for a single satellite after one hour Figure 4 6 Detection probability for both satellites after the first 6 hours 4 4 3 1 Hourly remap files on Windows The hourly remap files might take a lot longer to create using the included scripts These scripts contain a variable called DELTA which has been set to 6 hours The script will start with hours 1 through 6 and it will for each hour
24. n in Figure 3 2 Right click on the service and select Properties to set its start up type It should be Automatic This is a summary of http support microsoft com kb 137890 g Computer Management m File Action view Window Help e BMFBBBE m i m E Computer Management Local i System Tools fj Event Viewer a 2 Shared Folders AISDET_server Name Description E Local Users and Groups By NET Runtime Opti Microsoft Performance Logs and Alert Start the service NET Runtime Opti Microsoft a Device Manager Sy Adobe Active File M Tracks files Storage Removable Storage Sy Alerter Notifies sel Disk Defragmenter a Application Experie Processes Disk Management a Application Layer G Provides s i Services and Applications a Application Manage Processes i z Services R ASP NET State Ser Provides s i WMI Control Sa Automatic Updates Enables th BB Indexing Service u Background Intellig Transfers Sy ClipBook Enables Cli By COM Event System Supports 5 By COM System Appl Manages t z m H H i amp lt gt 3 gt N Extended Figure 3 2 Starting the AISDET server FFl rapport 2011 02300 11 3 1 3 Windows PowerShell It is necessary to have Windows PowerShell installed with a policy that allows it to run unsigned scripts It should be sufficient to execute Set ExecutionPolicy RemoteSigned in a PowerShell termina
25. nd 4 4 6 without running AISDET first This requires one file that list the MMSI latitude and longitude of each vessel and a set of files that lists reception and ground times for each decoded message A typical run would look something like the following amp C Program Files x86 AISDET bin aisent_dist exe s vessels txt d messages_satl txt messages_sat2 txt messages_sat3 txt p poygon_north_atlantic plg The vessels txt must contain one line per vessels and each line must be on the form MMSI latitude longitude The messages_sat txt files list every successfully decoded message Each file must begin with a common epoch header and then one line per message 2005 07 01 12 00 00 00 555533221 01 JUL 2005 21 10 40 000 01 JUL 2005 23 00 12 234 444422111 01 JUL 2005 19 31 00 000 01 JUL 2005 20 45 01 000 444422111 01 JUL 2005 21 09 50 000 01 JUL 2005 22 21 12 000 The first column is the MMSI which is followed by reception and ground time 30 FFl rapport 2011 02300 To see a simple user manual for aiscnt_dist execute amp CNProgram Files x86 AISDET bin aiscnt_dist exe h 5 Summary This software has been tested comprehensively but some bugs might still have gone by unnoticed and the packaging process might have introduced problems with missing files and or wrong files Any questions or bug reports may be sent to oystein olsen ffi no New features will not be added unless it is required by the work
26. o a Cc 2 Ke D g Q maps and times of detection Anterina model lonosphere maps STK animation Vessel density map Figure 2 2 The inputs to and outputs from AISDET 3 Installation The AISDET software collection requires a couple of external programs that compute satellite orbits and access times to ground stations and target areas These programs are included in the Heliosat installer 3 1 Windows 3 1 1 Installing Heliosat Heliosat is distributed as an ordinary Windows installer Heliosat 1 0 1 win32 exe It is strongly recommended to keep the default settings which includes installing to the path shown in Figure 2 1 even on a 32 bit OS AISDET includes some scripts and programs that assume C Program Files x86 as an installation prefix The installer will create a shortcut to remove Heliosat from the system under Start DAIl Programs FFI rapport 2011 02300 9 Heliosat Setup Choose Install Location Choose the Folder in which to install Heliosat Setup will install Heliosat in the following Folder To install in a different Folder click Browse and select another folder Click Next to continue Destination Folder E Program Files x86 Heliosat Space required 207 2MB Space available 37 8GB Figure 3 1 Recommended location of Heliosat 3 1 2 Installing AISDET The installer for AISDET is identical to the one for Heliosat and the same recommendations apply AISDET in
27. osphere This section is not used by AISDET and it is necessary to set the method to zero and filename to NONE The second section tells AISDET to load ionosphere data There are several different options but AISDET can only use CODE files Examples of data files can be found in C Program Files x86 Heliosaf share HeliosaNionosphere on Windows and in HOME share Heliosat ionosphere on Linux The shell script in the CODE folder can be used to download data for other years on Linux machines 4 2 3 Using the AISDET server Windows This assumes that server has been configured and is running All that is required to use the server is to create text files that define the work folder of the simulation See the server_partl txt and server_part2 txt files in the examples directory These files can be dropped into C AISSim server to start the jobs defined within these files The first file lists those jobs that will generate SOTDMA files The second file lists those jobs that require SOTDMA files as input Hence the second file cannot be dropped into C AISSim server before the relevant SOTDMA files have been generated This is not strictly true Both files can be dropped into C AISSim server at the same time as long as there are fewer cores on the workstation than SOTDMA generating simulations FFI rapport 2011 02300 17 It is strongly recommended to check that the simulations are correctly configured before
28. sels that are within communication range of one another AISDET assumes that any vessels within 20 nautical miles of one another can receive each other s messages AISDET assumes that vessels with Class A transponders transmit at 12 5W while vessels with class B transponders transmit at 2W They are given message repetition rates according to the distribution given in 1 AISDET assumes the same antenna radiation pattern for each vessel The pattern is modeled as a 5 8 dipole antenna mounted three meters above a perfect ground and with vertical polarization Its gain pattern resembles a doughnut with zero gain in the vertical The true radiation pattern depends on where the antenna is mounted on a vessel the materials shape and orientation of the vessel and reflections from the sea It is not feasible to model accurate antenna patterns for each vessel AISDET computes the polarization of the received signal if the satellite antenna is linearly polarized It takes into account Faraday rotation and assumes that the polarization was vertical at transmission This requires knowledge of Earth s magnetic field and ionosphere The Self Organizing Division Multiple Access 6 FFl rapport 2011 02300 International Geomagnetic Reference Field IGRF gives the Earth s magnetic field with an accuracy of 0 1nT from 2000 and onwards CODE2 produces global Total Electron Content TEC maps every second hour Figure 2 1 shows a contour plot of
29. stations in Cyprus and Madrid All Open seas 0 20 40 60 80 100 120 140 160 180 Timeliness minutes Fraction of detected vessels CDF Figure 4 10 The fraction of detected vessels in the North Atlantic as function of the time it takes to get the data to the user assuming ground stations in Cyprus and Madrid FFl rapport 2011 02300 27 Fraction of detected vessels All Open seas 0 20 40 60 80 100 120 140 160 180 Mean timeliness minutes Figure 4 11 Fraction of detected vessels as a function of the average time it takes to get data to the ground assuming ground stations in Cyprus and Madrid There is also a small script to summarize the results from the above analysis The following commands on Linux and Windows produce a small table that shows how many vessels the users can expect to get updates from within 60 and 180 minutes Linux cd HOME tmp examples dipoles mkdir update_timeliness_02_groundstations mv update_interval_ update_timeliness_02_groundstations mv timeliness update timeliness 02 groundstations mv cdfu update timeliness 02 groundstations mv cdft update timeliness 02 groundstations sh summarize update intervals sh update timeliness 02 groundstations 28 FFI rapport 2011 02300 Windows cd C Temp examples dipoles N aisent_dist PS1 mkdir update_timeliness_02_groundstations mv update_interval_ update_timeliness_02_groundstations mv timeliness_ update_timelin
30. such a map at 12 00 UTC on July 1 2005 The TEC value used to estimate Faraday rotation is calculated by linear interpolation between successive maps at the relevant time These calculations include the rotation of the ionosphere maps with respect to the Earth Figure 2 1 CODE produces global TEC maps every second hour The figure above shows a contour plot of such a map at 12 00 UTC on July 1 2005 AISDET requires a satellite antenna pattern to compute the received signal strengths The pattern can be selected from a set of ideal patterns or loaded from a file that describes the antenna pattern including polarization Section 4 2 2 4 describes the antenna setup in detail 2 2 Performance Assessment Method The SOTDMA protocol is designed to avoid transmissions of messages in the same slot for vessels within each other s field of view A satellite will receive multiple messages transmitted at the same time if there are more than a few hundred vessels within its field of view Furthermore messages transmitted in adjacent slots may interfere due to differences in travel times Bach interfering message has a specific Doppler shift which varies between 4kHz The interference from a message with a relative Doppler shift of 4 kHz is less than the interference from an identical message with no relative Doppler shift AISDET takes into account this effect either by integrating over the overlapping spectrums to determine the interference lev
31. wing command plots the total detection probability of one satellite plotprob_folder C Temp examples dipoles 11 0 1 15 1 0 Single satellite orbit 000 It is also possible to plot the accumulated detection probability over 15 orbits using both satellites plotprob_folder C Temp examples dipoles 1 1 15 1 0 Both satellites orbit 000 These maps contain detection probabilities for those 1x1 degree cells that contain at least one vessel see Figure 4 3 and Figure 4 4 0 6 0 4 0 2 0 Figure 4 3 Detection probability over one orbit using all antennas on a single satellite 20 FFI rapport 2011 02300 Figure 4 4 Final detection probability for both satellites after 15 orbits 4 4 2 1 Remap files on Windows The above plots require a set of remap files that aisdet_remap generates It uses a set of files that contain every message that can be decoded successfully with a probability of 10 or better aisdet_remap draws one uniform random number in the range 0 to 1 for each message A message is assumed to be successfully decoded if that number is less than the probability of decoding the message The SOTDMA files ensure that each antenna on one satellite sees the same message pool The messages will have different signal strengths at the sensor due to the different antenna patterns and or orientations A small user manual is available with this command amp C Program Files x86 AISDET bi
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