Earth Observation Mission CFI Software
VISIBILITY SOFTWARE USER MANUAL

Code	EO-MA-DMS-GS-016
Issue	4.26
Date	31/10/23

	Name	Function	Signature
Prepared by:	EOCFI Team	Project Engineers
Checked by:	Inês Estrela	Project Manager
Approved by:	Antonio Gutierrez	Division Head

DOCUMENT INFORMATION

Contract Data		Classification
Contract Number:	4000102614/1O/NL/FF/ef	Internal
Contract Number:	4000102614/1O/NL/FF/ef	Public
Contract Issuer:	ESA / ESTEC	Industry	X
Contract Issuer:	ESA / ESTEC	Confidential

External Distribution
Name	Organization	Copies

Electronic handling
Document generator:	Doxygen 1.7.1
Electronic file name:	eo-ma-dms-gs-016-10

Document Status Log

Issue	Change Description	Date
1.0	These libraries corresponds to version 4.0 of C libraries.	27/03/09
4.1	These libraries corresponds to version 4.1 of C libraries.	07/05/10
4.2	These libraries corresponds to version 4.2 of C libraries.	31/01/11
4.3	These libraries corresponds to version 4.3 of C libraries.	06/02/12
4.4	These libraries corresponds to version 4.4 of C libraries.	05/07/12
4.5	These libraries corresponds to version 4.5 of C libraries.	01/03/13
4.6	These libraries corresponds to version 4.6 of C libraries.	03/10/13
4.7	These libraries corresponds to version 4.7 of C libraries.	28/03/14
4.8	These libraries corresponds to version 4.8 of C libraries.	29/10/14
4.9	These libraries corresponds to version 4.9 of C libraries.	23/04/15
4.10	These libraries corresponds to version 4.10 of C libraries.	29/10/15
4.11	These libraries corresponds to version 4.11 of C libraries.	15/04/16
4.12	These libraries corresponds to version 4.12 of C libraries.	03/11/16
4.13	These libraries corresponds to version 4.13 of C libraries.	05/04/17
4.14	These libraries corresponds to version 4.14 of C libraries.	16/11/17
4.15	These libraries corresponds to version 4.15 of C libraries.	20/04/18
4.16	These libraries corresponds to version 4.16 of C libraries.	09/11/18
4.17	These libraries corresponds to version 4.17 of C libraries.	10/05/19
4.18	These libraries corresponds to version 4.18 of C libraries.	08/11/19
4.19	These libraries corresponds to version 4.19 of C libraries.	29/05/20
4.20	These libraries corresponds to version 4.20 of C libraries.	30/11/20
4.21	These libraries corresponds to version 4.21 of C libraries.	23/06/21
4.22	These libraries corresponds to version 4.22 of C libraries.	22/12/21
4.23	These libraries corresponds to version 4.23 of C libraries.	23/06/22
4.24	These libraries corresponds to version 4.24 of C libraries.	29/11/22
4.25	These libraries corresponds to version 4.25 of C libraries.	10/05/23
4.26	These libraries corresponds to version 4.26 of C libraries.	31/10/23

ACRONYMS, NOMENCLATURE AND TERMINOLOGY

Acronyms

ANX	Ascending Node Crossing
AOCS	Attitude and Orbit Control Subsystem
CFI	Customer Furnished Item
EF	Earth Fixed reference frame
ESA	European Space Agency
ESTEC	European Space Technology and Research Centre
FOS	Flight Operations Segment
GS	Ground Station
OSF	Orbit Scenario File
SCF	Swath Control File
SDF	Swath Definition File
SRAR	Satellite Relative Actual Reference
SSP	Sub Satellite Point
STF	Swath Template File
SUM	Software User Manual
TOD	True of Date reference frame
UTC	Coordinated Universal Time
UT1	Universal Time UT1
WGS[84	World Geodetic System 1984

Nomenclature

CFI	A group of CFI functions, and related software and documentation. that will be distributed by ESA to the users as an independent unit
CFI function	A single function within a CFI that can be called by the user
Library	A software library containing all the CFI functions included within a CFI plus the supporting functions used by those CFI functions (transparently to the user)

Notes in Terminology

In order to keep compatibility with legacy CFI libraries, the Earth Observation Mission CFI Software makes use of terms that are linked with missions already or soon in the operational phase like the Earth Explorers. This may be reflected in the rest of the document when examples of Mission CFI Software usage are proposed or description of Mission Files is given.

APPLICABLE AND REFERENCE DOCUMENTS

Applicable Documents

[GEN_SUM]

Earth Observation Mission CFI Software. General Software User Manual. EO-MA-DMS-GS-017. Issue 4.26 31/10/23

Reference Documents

[MCD]	Earth Observation Mission CFI Software. Conventions Document. EO-MA-DMS-GS-0001. Issue 4.26 31/10/23.
[MSC]	Earth Observation Mission CFI Software. Mission Specific Customizations. EO-MA-DMS-GS-0018. Issue 4.26 31/10/23.
[EE_COMMON_SUM]	Earth Observation Mission CFI Software. EECommon Software User Manual. EO-MA-DMS-GS-010. Issue 4.26 31/10/23.
[F_H_SUM]	Earth Observation Mission CFI Software. FileHandling Software User Manual. EO-MA-DMS-GS-011. Issue 4.26 31/10/23.
[D_H_SUM]	Earth Observation Mission CFI Software. DataHandling Software User Manual. EO-MA-DMS-GS-012. Issue 4.26 31/10/23.
[LIB_SUM]	Earth Observation Mission CFI Software. Lib Software User Manual. EO-MA-DMS-GS-013 Issue 4.26 31/10/23.
[ORBIT_SUM]	Earth Observation Mission CFI Software. Orbit Software User Manual. EO-MA-DMS-GS-014. Issue 4.26 31/10/23.
[POINT_SUM]	Earth Observation Mission CFI Software. Pointing Software User Manual. EO-MA-DMS-GS-015. Issue 4.26 31/10/23.
[FORMATS]	Earth Explorer File Format Guidelines. CS-TN-ESA-GS-0148.

INTRODUCTION

Classes and methods overview

This software library contains the CFI classes required to compute time segments at which an Earth Observation satellite, or one of its instruments is in view of various targets:

zones (defined as polygons or circles, on the earth ellipsoid or at a given altitude)
ground stations
data relay satellites
stars

The following classes are included:

OrbitExtra: Class to extract orbital extra information.
Swath: Class to make operations involving a swath for zone and station visibility.
SwathStar: Class to make operations involving a swath for star visibility.
VisibilityList: Class to store list of visibility segments.
VisibilitySegment: Class to store a visibility segment.

and the following auxiliary classes also (defined in VisibilityData.h):

VisExtraInfo: Base class for visibility extra information.
ZoneExtraInfo: Additional information to visibility segments computed for one zone.
StationExtraInfo: Additional information to visibility segments computed for one station.
MultiZonesExtraInfo: Additional information to visibility segments computed for multiple zones.
MultiStationsExtraInfo: Additional information to visibility segments computed for multiple zones.
MappingExtraInfo: Additional information to visibility segments computed for mapping.
StarExtraInfo: Additional information to star visibility segments.
OrbitExtraInfo: Orbit extra information.
ScfAppear: Swath Control File appearance data structure.

This library is to be used for planning of Earth Observation operations. It includes, the following CFI methods:

SwathStar::starVisTime: computes visibility time segments for a star.
Swath::stationVisTime: compute visibility time segments for a ground station
Swath::zoneVisTime: compute visibility time segments for an instrument swath in visibility of a zone.
Swath::getPos: computes location of a swath at a given time (additional routine to help refine the results of zoneVisTime)
Swath::multiZonesVisTime: computes the visibility segments of several zones and sort them to different criteria.
Swath::multiStationsVisTime: computes the visibility segments of several ground stations and sort them according to different criteria.
Swath::genSwath generate the instrument swath template file for a given satellite, instrument mode and orbit.
Swath::genScf generates a swath control file for the ESOV tool.
Time Segments Manipulation Routines:
- VisList::not: returns the complement of 1 vector of time segments.
- VisList::and: returns the intersection segments from 2 vectors of time segments.
- VisList::or: returns the joined segments from 2 vectors of time segments
- VisList::delta: add or subtract time durations at the beginning and end of each time segment in a vector.
- VisList::sort: returns the vector of time segments sorted according to absolute or relative orbits.
- VisList::merge: merges all the overlapped segments in a list.
- Swath::mapping: returns a subset of the time segments vector, such that this subset covers entirely a zone or line swath.

Several files are required to operate properly the above methods:

Orbit Scenario File (all functions)
Swath Template Files (Swath::stationVisTime, Swath::zoneVisTime, Swath::getPos)
Ground Stations Database File (Swath::stationVisTime)
(optionally) Zones Database File (Swath::zoneVisTime)
(optionally) Star Database File (Swath::starVisTime)

Calling Sequence

An overview of the data flow is presented in following figure:

LIBRARY INSTALLATION

For a detailed description of the installation of any CFI library, please refer to [GEN_SUM].

LIBRARY USAGE

Note that to use the Visibility software library, the following other CFI software libraries are required:

EE_COMMON
FILE_HANDLING
DATA_HANDLING
LIB
ORBIT
POINTING

Third party libraries:

POSIX thread library: libpthread.so (Note: this library is normally pre-installed in Linux and MacOS platforms. For Windows platforms, pthread.lib is included in the distribution package, with license LGPL)
GEOTIFF, TIFF, PROJ, LIBXML2 libraries (these libraries are included in the distribution package. Their usage terms and conditions are available in the file "TERMS_AND_CONDITIONS.TXT" which is part of the distribution package).

In order to improve run-time performance, Some Pointing functions (see [POINT_SUM]) perform their computations in multi-threading mode. The multi-threading code of the Pointing functions uses the OpenMP API (see http://en.wikipedia.org/wiki/OpenMP). OpenMP is not supported in the clang compiler, therefore such functions work in single-thread mode in MacOS.

To use the Visibility software library in an user application, that application must include in its source code the header files where the classes that are going to be used are defined.
To link correctly this application, the user must include in his linking command flags like (assuming cfi_lib_dir and cfi_include_dir are the directories where respectively all CFI libraries and include files have been installed, see [GEN_SUM] for installation procedures):

LINUX:
-Icfi_include_dir -Lcfi_lib_dir
-lCfiVisibility -lCfiPointing -lCfiOrbit -lCfiLib -lCfiDataHandling -lCfiFileHandling -lCfiEECommon -lm -lc -fopenmp
MacOS:
-Icfi_include_dir -Lcfi_lib_dir
-lCfiVisibility -lCfiPointing -lCfiOrbit -lCfiLib -lCfiDataHandling -lCfiFileHandling -lCfiEECommon -lm -lc
Note: the EOCFI libraries are built using the switch -mmacosx-version-min=10.9 for backward compatibility, so the libraries are built for STL library libstdc++.
Starting from Mavericks the default STL library is libc++, so link problems can appear if you do not use the same build switch as the EOCFI
WINDOWS (dynamic libraries):
/I "cfi_include_dir" /libpath:"cfi_lib_dir"
libCfiVisibility.lib libCfiPointing.lib libCfiOrbit.lib libCfiLib.lib libCfiDataHandling.lib libCfiFileHandling.lib libCfiEECommon.lib
WINDOWS (static libraries):
/I "cfi_include_dir" /libpath:"cfi_lib_dir"
libCfiVisibility.lib libCfiPointing.lib libCfiOrbit.lib libCfiLib.lib libCfiDataHandling.lib libCfiFileHandling.lib libCfiEECommon.lib pthread.lib libxml2.lib libgeotiff.lib libtiff.lib libproj.lib Ws2_32.lib

Note that, as Earth Observation CFI libraries are dynamic, cfi_lib_dir must be included in the path where the system looks for dynamic libraries (LD_LIBRARY_PATH in LINUX, DYLD_LIBRARY_PATH in MacOs). For WINDOWS system, the executable will look for .dll libraries, not the .lib ones that are used to create the executable, so they must be in the path described by PATH variable.
All the classes described in this document are defined in EECFI namespace, to avoid any possible conflict with classes of other libraries, so the user must choose one of the following two options in order to use the classes:

Inserting using namespace EECFI; in the code.
Using the classes with the namespace prefix (e.g.: EECFI::OrbitFile orbitFile;)

ERROR HANDLING

The error management in C++ Visibility is made throw exceptions, that is, if any error is produced, an exception of type CfiError is thrown and it must be catched putting the code inside a try-catch block.
See [GEN_SUM] to know more about how to handle the CFI errors. For a descripton about the CfiError class and its methods, see [EE_COMMON_SUM].