• INFO

• Abbreviations
• Entire Online Help

GPS, EGNOS, GLONASS, GALILEO

These branches contains all analysis and status information on the GNSS constellations.

The three second level menus are:

• Analysis which presents post processed analysis of the GNSS system where you can find three lower level menus:
  • Position (domain analysis)
  • Integrity (domain analysis, EGNOS and GALILEO only)
  • Receiver Tracking (analysis)
  • Signal In Space (domain analysis, GPS, GLONASS, GALILEO)
  • EGNOS messages (EGNOS only)
• System Information which is a mirroring of official system operator information, in this case that of the U.S. Coast Guard containing:
  • GPS from USCG (Status, Notices, Almanac)
  • EGNOS from ESSP (Status, Notices)
  • GLONASS from IANC (Status, Notices, Almanac)
  • GIOVE from ESTEC and CelesTrak* (Status, TLE*)
• Data containing all data in ASCII format produced by GalTeC for the Analysis. These are input data from the GalTeC Receivers, intermediate data and some results data.
  Note: The Data section is visible only for registered users!

The calendar control is explained here. At the actual date no information is available besides in the Simulation branch. The availability of the content is as follows:

• Position and Receiver Tracking: the previous day (GMT) and older, because of waiting for the logging of the actual day.
• For EGNOS: Integrity and EGNOS Messages, also of the previous day and older.
• Signal In Space: two weeks and older, because of waiting for IGS final products.
• System Information: from today, but not necessarily from 00:00 GMT on, we depend on System Operators update!
• Data and Result Files availability is coupled to the availability of the information mentioned above.

Please understand that for GALILEO - while the sub-menu structure is fully prepared, only few content can be provided until the GALILEO program is not in its IOV phase and beyond.

Analysis

In the overview of the 'GNSS' page (which is also the 'Analysis' page) you see the rating of the basic characteristics:

Position Accuracy (All 4 GNSS) Protection Level Availability (only EGNOS and GALILEO) Integrity (only EGNOS and GALILEO) Signal in Space Accuracy (not EGNOS)

they will be rated textually and signaled by a "traffic" light. The rating is an 'own' rating by GalTeC and not by the systems itself ! It is still experimental!

"Position Accuracy..."

The GNSS quality is rated by statistically analysing of the position output of a related GalTeC Receiver, configured with an elevation mask of 5 degrees.

The rating of the position accuracy is based on a comparison of the position output with the geodetically precisely surveyed position of the stationary receiver antenna.

The rating is currently evaluated against the required accuracies for aviation applications (approaches with the category APV-II, according to ICAO SARPS for Radio navigation Systems), which is:

The statistic is sampled over the 86400 seconds of a day. Please note that no check is performed about a maximum error itself (outliers), which however will influence the statistic.

ATTENTION: This is not equivalent to the related GNSS guaranteed bound of the Standard Positioning Service (which is e.g. for GPS vertically 15 meters @95% and global averagec) !

The rating may take the values (colour):

• (green) = OK:
  meaning horizontal and vertical accuracy below the above values
• (yellow) = OK with 5% extra margin:
  meaning horizontal or vertical accuracy only slightly above the above values
• (red) = Not OK:
  meaning horizontal or vertical accuracy are clearly above the required values.
• (black) = Position computation is not available:
  meaning that the receiver could not compute a position the whole day for some reason. But there is a valid position file.
• (grey) = Analysis not available:
  meaning that even a position file is not available that day (i.e. no related file found for processing in the GalTeC data base).

The information and rating is representing the analysis graphics found one level further down: click on Position.

"Protection Level Availability..."

EGNOS branch only (and provisionally prepared for GALILEO)

The GalTeC EGNOS capable receiver delivers SBAS Protection levels: HPL and VPL.

The rating of the Protection Level availability is related on a statistic how often during the day both HPL and VPL are lower than the corresponding Alert Limits HAL and VAL.

The rating is currently evaluated against the required Alert Limits for aviation applications (approaches with the category APV-II, according to ICAO SARPS for Radio Navigation Systems), which is:

The statistic is sampled over the 86400 seconds of a day.

ATTENTION: This is not equivalent to the EGNOS guaranteed Service Level (which is APV-I related)!

The rating may take the values (colour):

• (green) = OK:
  meaning xPL<xAL availability is 99.0% or higher
• (yellow) = OK with extra margin:
  meaning xPL<xAL availability is between 95.0% and 99.0%
• (red) = Not OK:
  meaning much too high False Alert rate (>5%)
• (black) = Protection Level computation is not available:
  meaning that the receiver could not compute a position and xPL the whole day for some reason. But there is a valid position/xPL file (pos_vel.dat).
• (grey) = Analysis not available:
  meaning that even a position/xPL file is not available that day (i.e. no pos_vel.dat found for processing in the GalTeC data base).

The information and rating is representing the analysis graphics found one level further down: click on "Integrity".

"Integrity..."

EGNOS only (and provisionally prepared for GALILEO)

The GalTeC EGNOS capable receiver delivers SBAS Protection levels: HPL and VPL.

The rating of the Integrity is based on the comparison of so called HMI (Hazardous Misleading Indication) events, i.e. the Position Error (Vertical or Horizontal) is over the Alert Limit and the related Protection Level is NOT.

The rating is currently evaluated against the required Alert Limits for aviation applications (approaches with the category APV-II, according to ICAO SARPS for Radio Navigation Systems), which is:

The statistic is sampled over the 86400 seconds of a day. So 1 second of Non-Integrity represents 1.16x10^-5 per second or 0.7x10^-7 per 150 seconds

ATTENTION: This is not equivalent to the EGNOS guaranteed Service Level (which is APV-I derived)!

The rating may take the values (colour):

• (green) = OK:
  meaning not even for 1 second an Non-Integrity event occurred
• (red) = Not OK:
  meaning there was at least for 1 second a HMI-Integrity event in the day. Please note: Time To Alarm is not assessed here.
• (black) = Protection Level computation is not available:
  meaning that the receiver could not compute a position and xPL the whole day for some reason. But there is a valid position/xPL file (pos_vel.dat).
• (grey) = Analysis not available:
  meaning that even a position/xPL file is not available that day (i.e. no pos_vel.dat found for processing in the GalTeC data base).

The information and rating is representing the analysis graphics found one level further down: click on "Integrity".

"Signal In Space Accuracy..."

The GNSS Signal in Space quality is rated by statistically analysing each GNSS satellite in the so called Signal In Space domain, this means the error components: Satellite Position (Orbit) Error and Clock error. Other satellite related errors are assumed to be included in these terms. So it represents a part of the Pseudorange accuracy (without Ionosphere, Troposphere and local effects).

The Orbit and Clock errors are computed by comparing the IGS final products on Orbits and Clocks of the GNSS satellites, related to the solutions obtained from the GNSS broadcast Ephemeris data for each individual epoch. Ephemeris recorded from several IGS stations around the world are considered so that for each GNSS satellite a round the clock analysis is possible. (No data from our receiver in Stuttgart is used here.)

The sampling is done over 24 hours of a day with intervals of 1 minute by interpolating and synchronising the two Orbit and Clock processing results.

The error in range (SIS portion) domain is called at GalTeC SISRE (SIS Reference Error).

GPS:

For the rating of SIS quality it is checked for each GPS satellite, how much percent the SISRE is >= the broadcast URA. Since URA should represent a predicted 1-sigma of the SISRE (URE in GPS terminology), GalTeC checks how in how much epochs (1 min sampling) SISRE is >= URA in percent. This percentage is expected to normally be higher than 68.23% which is related to a 1-sigma bound for a Normal distribution.

ATTENTION: This is not the official GPS understanding of performance criteria stated in GPS SPS.

The rating for each individual GPS satellite may take the values (colour):

• (green) = OK:
  meaning SISRE <= URA in 68.27% or more
• (yellow) = OK with 5% extra margin:
  meaning SISRE <= URA between 63.27% and 68.27%
• (red) = Not OK:
  meaning URA was too optimistic
• (black) = Position computation is not available:
  meaning either there exists no satellite or it is flagged unhealthy. Then GalTeC processing which produces SISRE ignores it. If at least 50% of the data are not available the satellite will be flagged also black.
• (grey) = Analysis not available:
  meaning that even a sisre file containing all satellites is not available that day (i.e. no related file found for processing in the GalTeC data base).

The rating on this page for all GPS satellites at the same time is coded as follows:

• grey if no results are available in the data base
• only black colour is found in the SIS summary!
• red, if any satellite is flagged as red
• yellow, if any satellite is flagged as yellow (and no one with red!)
• green, if any satellite is flagged green. In black and grey flagged satellites being ingnored.

The information and rating is representing the analysis graphics found one level further down: click on Signal in Space.

GLONASS:

While the look-alike in the GLONASS branch is exatly the same as with GPS, for GLONASS currently NO evaluation is performed by GalTeC as no URA-analogue parameter is broadcast. The 'traffic lights' are set to "Yellow" if analysis results are available for a satellite or "Black" or "Grey" if not available.

GALILEO:

While the look-alike in the GALILEO branch is exactly the same as with GPS, for GALILEO currently NO evaluation is performed by GalTeC due to: Not broadcast SISA (which would be a URA equivalent) and currently not possible GALILEO SISRE computation.

Analysis Result Files

Only Registered users will see and be able to download on this page the ASCII result text files generated by GalTeC. These three files are generated by the Analysis software together with the plots shown in the lower level menus. The content is more or less self explaining, but some explanationary documents can be found under Home -> Documents in the GalTeC Products Catalogue.

top of page

---

Analysis - Position

The Position Analysis and Graphic page shows various plots.

On the Position page you can find 6 plots showing the Position output and its reference to True Position of the stationary GalTeC GNSS receiver installation (location: Stuttgart, Germany as described in help section Data - Receivers). The receiver is configured with an elevation mask of 5 degrees and gives a position output each second. Its antenna has a clear visibility of sky.

First the main results are presented in textual form. It is the Vertical and Horizontal accuracy 95% statistic over the day.

The plots are generated on a daily basis by the GalTeC Real data analysis. Besides the graphics registered users may download results in ASCII format on the next higher level page (Analysis). They also can download the Position ASCII file over which the analysis was performed (menu Data, visible only to registered users).

The following plots are on display:

"Positioning Quality - Position Fixes (2-D)":

This plot shows the 2D-Position errors, containing the divergence in East (longitude) and North (Latitude) direction compared to the reference position. Differences in latitude and longitude are converted to metric unit and plot for each epoch as green '+' (usually 86400 crosses).

Additionally the plot shows the 95% accuracy of these errors (solid green circle) and the APV-II* requirement (dashed magenta circle). So the green circle (which is often hidden in the + cloud) should be smaller than the magenta circle.

The annotation box on the top gives the date of observation and station name.

In the lowest box the numerical value for the 95% accuracy, which means 95% of the position points are inside the green circle, the maximum absolute errors in East and North direction and the APV-II requirement are printed as main results.

* Approach (Procedure) with Vertical Guidance (aviation requirement of ICAO)

"Positioning Quality - Horizontal":

This plot shows the horizontal errors along the 24 hours of a day. The horizontal error (green line) consists of the divergence in East (longitude) and North (latitude) direction compared to the reference position. Differences in latitude and longitude are converted to metric unit. The norm of both components is computed and therefore the horizontal error is always positive.

Additionally the plot shows the 95% accuracy of this error (dashed green line, often hardly visible within the shaky green line band) and the APV-II* requirement (dashed magenta line). The position accuracy is OK when the green dashed line is lower than the magenta line.

In the annotation box (middle) the numerical value of the 95% accuracy is given, which means 95% of the horizontal errors are below this bound. Also the maximum horizontal errors and the APV-II requirement are shown. In the right box some information about date of observation, station name and sampling interval are given.

* (see above)

"Positioning Quality - Vertical":

This plot shows the vertical errors along time. The vertical error (blue line) is the divergence in height component compared to the reference position. This value can be positive or negative.

Additionally the plot shows the 95% accuracy of this error (dashed blue lines) and the APV-II* requirement (dashed magenta lines). The 95% bounds are always symmetrical with respect to the 0-line! They should be inside the magenta lines.

In the annotation box (middle) the numerical value of the 95% accuracy is given, which means 95% of the vertical errors are within the area of the two blue dashed lines.

Also the maximum vertical error and the APV-II requirement are written in this box. In the right box some information about date of observation, station name and sampling interval are given.

* (see above)

"Distribution of Position Errors – Direction: North"

The next plots show the position error distribution in each of the three local geographic directions: North, East and Up.

For example this plot shows the real distribution of the error in the North direction (histogram). The numbers of samples which are in a defined class are drawn as light green bars. Each of the 31 classes comprises one meter (e.g. -0.5 – 0.5 m, bar around zero).

All errors which are outside the plot bounds (-15.5 m and +15.5 m) are collected in the bars at the most left or right.

The tick numbers of the y-axis has to be multiplied with a scale factor [see squared brackets].

The solid green line shows the computed normal representation distribution of the North error. First in a standard way the mean and standard deviation is computed and from there the Gaussian curve drawn. A scale factor of 10 000 is additionally applied to pull the curve up to the level of the bars.

In the annotation box on the right top the date of observation and the station name is given. In the box below the mean error (bias) and the corresponding standard deviation as well as the total number of samples are listed.

Axes limits:
X-axis: [-15.5 : 1 : 15.5], Classes [meters]
Y-axis: [0: 1 : 10], Frequency * [scale factor]

The other similar plots are in the direction East and Up.

top of page

---

Analysis - Integrity

Note: The Analysis - Integrity is only available for the systems EGNOS and GALILEO.

On the Integrity page you can find 4 plots showing the Protection Level output of the receiver versus the measured error of the position output. The position and SBAS protection level are taken from a stationary Septentrio PolaRx2 receiver, configured with an elevation mask of 5 degrees and gives a position output each second. Its antenna has a clear visibility of sky.

First the main results are presented in textual form. These are the availability percentages of HPL and VPL being lower than the corresponding alarm limits. And these are the counted integrity failures (vertical and horizontal, independently).

The plots are generated on a daily basis by the GalTeC Real data analysis. Besides the graphics registered users may download results in ASCII format on the next higher level page (Analysis). There are also some more statistics on Integrity found reflecting different cases (e.g. correlation of vertical and horizontal results)

They also can download the Position (pos_vel) and Protection Level (dop_xpl) ASCII files over which the analysis was performed (menu Data, visible only to registered users).

The following plots are on display:

Integrity and Availability - Horizontal (Time plot):

This plot shows the horizontal position errors (dHor ° HPE) and the protection levels of each time epoch. The HPE (green line) consists of the divergence in East (longitude) and North (latitude) direction compared to the reference position. Differences in latitude and longitude are converted to metric unit. The norm of both components is computed and therefore the horizontal error is always positive.

The horizontal protection level (HPL) is derived from the receiver and drawn in red. Additionally the horizontal alarm limit (HAL, relating to APV-II requirement) is shown (magenta dashed line).

In the annotation box in the middle the maximum HPL and HPE values are given. The percentage of cases in those HPL < HAL and the HPL gaps (i.e. no HPL available) is depicted in this box too.

In the right box some information about the date of observation, station name and sampling interval are given.

* Approach (Procedure) with Vertical Guidance (aviation requirement of ICAO)

Integrity and Availability - Horizontal (Stanford plot):

This plot is a so called Stanford plot that summarizes availability and integrity events for the horizontal case. The horizontal position errors (HPE) are drawn versus the horizontal protection level (HPL). The cases are plotted as pixels of HPE/HPL pairs and the frequency is shown with a colour coding (see colour bar at the right).

In GalTeC a modified representation is used derived from ICAO asked requirements. The plot is divided in four rectangles by the horizontal alarm limit line (HAL = 40 m). c The lower left rectangle (white colour) contains all:

• normal availability cases (HPE<HAL ∧ HPE<HPL, see upper white triangle)
• and the acceptable misleading indication (HPE<HAL ∧ HPE>HPL, see lower light shaded triangle.)
  That the misleading information in the lower light shaded triangle are "acceptable" or "harmless" is a GalTeC interpretation of requirements, where only Hazardous Misleading Information probability is specified. System operators often regard this sector as "not acceptable".

The upper left rectangular sector (yellow) indicates the section of false alarm (HPE<HAL ∧ HPL>HAL).

The upper right rectangle represents the true alarm (grey) sector, (HPE>HAL ∧ HPL>HAL). There is no difference between HPE><HAL as it makes operationally no difference. Again System operators may see it differently.

Finally the lower right section (red) indicates the hazardous misleading indication (HPE>HPL ∧ HPL<HAL), which should happen very rarely (2x10-7) according to the APV-II requirements.

It is important to understand that the percentages given in the graphic sectors are related to the available number of valid samples, which may be less than the seconds of a day. Therefore the availability in the graph can be 100% while the absolute availability is 50% (see annotation boxes below), when EGNOS was half the day offline.

At the right two annotation boxes give some additional information and the main results.
The upper box gives the date of observation and station name.

The yellow medium box gives the main numerical results of the integrity analysis:

• Absolute Availability is related to the 86400 seconds of the day, including the HPL gaps delivered by the receiver (i.e. epochs with no HPL solution at all). This is the value to be rated against the APV-II requirement (99.5%). The Absolute Unavailability is the inverted value.
• HMI Events is a cases counter taken over from the red sector.
• Timeframe is the number of seconds in a day, ergo always 86400.
• Valid Epochs are these where HPL was computed by the receiver (not always the case, see above).
• Observation Interval is normally 1 second (output frequency of the receiver)
• Missing Epochs are these where the receiver failed to compute HPL (e.g. due to timeouts of the SBAS corrections, or SBAS transmission gaps)

Integrity and Availability - Vertical (Time plot):

This plot is to be read just like the horizontal one. The Vertical Alarm Limit is however 20 meters only in the case of APV-II. The vertical axis range is lower with max 40 meters instead of 60.

If you compare with the position error plot in the Position menu, then please note that here the absolute value of vertical errors is plot against the (positive) protection level.

Integrity and Availability - Horizontal (Stanford plot):

This plot is to be read as the Horizontal one. The Vertical Alarm Limit is however 20 meters only in the case of APV-II.

top of page

---

Analysis - Receiver Tracking

The section 'Receiver Tracking' informs about the GalTeC Receiver tracking on which the Analysis in Position is performed. It shows two plots:

"DOP and Number of Satellites" (currently not for GALILEO):

This plot shows the number of the position solution used satellites (red line), the horizontal dilution of position (HDOP, green line) and the vertical dilution of position (VDOP, blue line) with time. The right information box contains date of observation, station name and sampling interval. The box in the middle includes maximum of HDOP and VDOP and the minimum and maximum number of satellites.

"Tracked Satellites at Receiver Station":

This plot shows all tracked satellites at the given reference station along time. For every tracked GNSS satellite ID a horizontal line is plotted.

In the annotation box on the left station and receiver name are given. In the right box date of observation and GNSS system is shown.

top of page

---

Analysis - EGNOS Messages

"SBAS messages transmitted via GEO:"

This plot shows all SBAS messages transmitted by the actual satellite over the day. For every received SBAS message one blue dot will be printed. Therefore a line over time will be printed for each often received Message Type.

On the right border of the plot the total number of received messages of each type is presented numerically.

The left annotation box contains the satellite ID (PRN), the augmentation system and the sum of all received SBAS messages. In the right box date of observation, station and receiver name are printed.

Registered users may download an ASCII table file, which content has been plot here, to have a high resolution view on the transmit sequence of message types - see Data menu.

top of page

---

Analysis - Signal in Space

On this page you can see the information on GNSS SIS quality (in pseudorange domain). On top you see the rating of each of the possible GNSS satellites:

• 32 GPS (ID=PRN)
• 24 GLONASS (ID=Slot Number)
• 36 GALILEO or currently, 2 Giove

GPS:

For GPS the following colour scheme is used:

• (green) = OK:
  meaning SISRE <= URA in 68.27% or more, i.e. URA covers the errors
• (yellow) = OK with 5% extra margin:
  meaning SISRE <= URA between 63.27% and 68.27%
• (red) = Not OK
  meaning URA was too optimistic and does not represent the real errors
• (black) = Position computation is not available:
  meaning either there exists no satellite or it is flagged unhealthy. Then GalTeC processing which produces SISRE ignores it. If at least 50% of the data are not available the satellite will be flagged also black.
• (grey) = Analysis not available:
  meaning that even a SISRE file containing all satellites is not available that day (i.e. no related file found for processing in the GalTeC data base).

ATTENTION: This is not the official GPS understanding of performance criteria stated in GPS SPS.

GLONASS:

While the look-alike in the GLONASS branch is exactly the same as with GPS, for GLONASS currently NO evaluation is performed by GalTeC as no URA-analogue parameter is broadcast. The 'traffic lights' are set to "Yellow" if analysis results are available for a satellite or "Black" or "Grey" if not available.

GALILEO:

While the look-alike in the GALILEO branch is exactly the same as with GPS, for GALILEO currently NO evaluation is performed by GalTeC due to: Not broadcast SISA (which would be a URA equivalent) and currently not possible GALILEO SISRE computation.

You can click on each SVID number to obtain results of that satellite. You will find individual satellite analysis results first in text form with the main results. When you click on all behind the last SVID the plots for all satellites will be presented in sequence in one window (you can scroll all the way down to see the difference).

Status:

For GPS

• (green) = OK:
  meaning SISRE <= URA in 68.27% or more
• (yellow) = OK with 5% extra margin:
  meaning SISRE <= URA between 63.27% and 68.27%
• (red) = Not OK
  meaning URA was too optimistic
• (black) = Position computation is not available:
  meaning either there exists no satellite or it is flagged unhealthy. Then GalTeC processing which produces SISRE ignores it. If at least 50% of the data are not available the satellite will be flagged also black.
• (grey) = Analysis not available:
  meaning that even a SISRE file containing all satellites is not available that day (i.e. no related file found for processing in the GalTeC data base).

For GLONASS as no URA or similar parameter is broadcast

• (yellow)
  meaning SISRE for that satellite has been calculated (plots available)
• (black)
  meaning either there exists no satellite or it is flagged unhealthy. Then GalTeC processing which produces SISRE ignores it. If at least 50% of the data are not available the satellite will be flagged also black
• (grey) = Analysis not available:
  meaning that even a SISRE file containing all satellites is not available that day (i.e. no related file found for processing in the GalTeC data base).

For GALILEO the only displayed status is

• (grey) = Analysis not available:
  meaning that even a SISRE file containing all satellites is not available that day (i.e. no related file found for processing in the GalTeC data base).

24 hour statistical values:

SISRE >= URA: the percentage over a day, leading to the GalTeC colour coding of the satellite.

URA OK: is Yes (>=68.27%) or No (lower %). It is taken from the third graph. Finally the SISRA (for the day) is printed in textual form. It is taken from the fourth graph. For GLONASS it is obviously always 0% (i.e. not applicable).

SISRA: numerical value (in meters) It is taken from the fourth plot and is valid for GPS and GLONASS (but currently not for GALILEO).

You can find below for the selected satellite 4+2 plots showing the Signal In Space accuracy, which is part of the whole error budget on a pseudorange (the green background plots). In addition our observations at receiver level is shown in form of pseudorange residuals (the orange background plots) for reference.

The SIS accuracy including only satellite position errors resulting from Ephemeris application and satellite clock error after application of the Navigation Message clock parameters. As reference ('truth') the IGS precise orbit & clock files for GPS are used. The rule is Ephemeris orbit minus 'true' orbits (or clock respectively).

For the clock errors comparison between ephemeris and sp3 data, caution must be exercised. The broadcast clock corrections are of course referenced to the GPS system time, but the IGS precise clock (corrections) are referenced to the IGS System Time (IGST). As a work around, we correct these clock corrections by the estimated time difference between these two scales. Therefore you will find a difference between the dClock plot and the dClock column in the SISRE.dat files (for registered users under the sub menu: Data -> GPS Processed Data).

The difference between the satellite position vectors and clocks and the projection to a pseudorange (line of sight direction is called at GalTeC SISRE (SIS Reference Error) and is equivalent to the URE in the terminology of GPS. The line of sight is from the satellite to a worst user location where the orbital errors maximise when projected to the line of sight.

The plots are generated on a daily basis, but with a two week delay with respect to the actual day, since we depend on availability of the IGS precise products.

Besides the graphics registered users may download results in ASCII format on the next higher level page (Analysis).

They also can download the SISRE ASCII file over which the analysis was performed (menu Data, visible only to registered users).

The following 6 plots are on display:

"Satellite Position Errors"

This plot shows the 3 components of the orbit (or satellite position) error along time:

• along track – divergence in direction of motion,
• across track – divergence perpendicular to the direction of motion,
• radial – divergence in direction of the earth centre

Additionally the epochs of IODE (Issue of Data Ephemeris) changes are marked with magenta diamonds (GPS plots only). It is here without effects due to the filters in the orbit determination using all ephemeris sets. In the information box in the middle - the date of observation, the GNSS system and satellite ID (PRN in case of GPS) is shown. The right box contains the numerical values for the maximum errors in all three components.

"Satellite Clock Errors"

This plot shows the satellite clock error component of SISRE. The clock error was converted to metric unit (multiplication with speed of light) and plotted as black line. Additional the epochs of IODE (Issue of Data Ephemeris) changes are again marked with magenta diamonds (GPS plots only). In the information box in the middle date of observation, GNSS system and satellite ID is shown. The right box contains the numerical value for the maximum clock error.

"SISRE to Worst User Location"

This plot shows the SISRE (Signal-in-Space Range Error) projected to range (for a worst user location) along time. The SISRE is plotted as blue curve. It represents the total error on a pseudorange from the space component.

In case of GPS: The URA (User Range Accuracy) which shall be representing a one-sigma of these errors and is broadcast by GPS derived from the receiver is drawn as dashed magenta line and the epochs of IODE (Issue of Data Ephemeris) changes are marked with magenta diamonds. In the information box in the middle – the date of observation, the GNSS system and satellite ID (PRN) is shown. The right result box contains the numerical values for the percentage of cases in those SISRE <= URA (blue curve is within the magenta dashed lines).

In case of GPS and GLONASS: The maximum deviation of SISRE (positive or negative) is also shown in the yellow annotation box.

"Distribution and Bounding through SISRA"

This plot shows the distribution of SISRE (Signal-in-Space Range Error) and the corresponding normal representation (gaussian curve, blue line). The numbers of samples which are in a defined class are drawn as light blue bars. Each of the 31 classes comprises one meter (e.g. -0.5 – 0.5 m, bar around zero). All errors which are outside the plot bounds (-15.5 m and +15.5 m) are collected in the bars at the most left or right class. The scale of the y-axis has to be multiplied with a scale factor (see squared brackets). The solid blue line shows the normal distribution of SISRE.

The solid green line is the bounding distribution of SISRE with a forced zero mean. Its standard deviation is the SISRA parameter. The SISRA of the day is defined as standard deviation of the bounding distribution (green line) that 68.23% of samples are within -SISRA and +SISRA.

Below the graph the mean and standard deviation of normal (blue) and bounding (green) distribution is marked with squares and circles.

In case of GPS: Additionally the broadcasted URA's (User Range Accuracy) are displayed with magenta circles as representatives of standard deviations (mean=zero). Normally the magenta markings should be inside the green markings. However the SISRA is resulting from a whole day statistic where the URA are valid for parts of day (e.g. 2 hours). So here no strict decision criteria can be derived whether each URA was correct. However in the results ASCII file, which can be retrieved by registered users in the root menu (GPS/Analysis) a SISRA is listed for the validity time of each URA.

In the annotation box in the middle - the date of observation, the GNSS system and the satellite ID is given. In the right box the mean and the standard deviation of SISRE (compare blue markers at bottom), the SISRA (Signal-in-Space Range Accuracy) and the total number of samples are listed.

"Pseudorange Residual based UERE"

This plot shows the pseudorange residual errors along time, which was computed by the GalTeC local receiver in the configuration Single Frequency (L1) GPS. Therefore all error sources are included. The blue line represents the residual error of the pseudorange (alias UERE, User Equivalent Range Error). This is obviously a local performance and not of the GNSS alone (contrary to the first four green background plots). With it a cross check could be done related to the SIS only errors. However note that errors can be reduced due to opposite sign local error components. Also please note that SISRE is computed for a worst user location in a satellites footprint. This is most likely another location than the GalTeC receiver location, maybe thousands of miles away. In the left annotation box the satellite ID, the sampling interval and the maximum absolute residual error is printed. In the right box the date of observation, GNSS system, station and receiver name is given.

"Histogram of UERE"

This plot shows the distribution of the pseudorange residual errors. The numbers of samples, which are in a defined class are drawn as light blue bars. Each of the 31 classes comprises one meter (e.g. -0.5 – 0.5 m, bar around zero). All errors which are outside the plot bounds (-15.5 m and +15.5 m) are collected in the bars at the most left or right. Note – the numbers on the y-axis have to be multiplied with a scale factor (see squared brackets). The solid blue line shows the normal representation of the distribution, based on the computed mean and standard deviation of the samples - which is solvable mathematically for any real distribution form. In the annotation box in the middle the date of observation, GNSS system and satellite ID is given. In the right box the maximum and the mean residual error and the corresponding standard deviation (1–sigma) as well as the total number of samples are listed.

top of page

---

System Information

In this branch some information from the official sites of the GNSS systems are mirrored.

The following lists show the provided information for each GNSS and its sources.

The system information pages allow an immediately preview of the files. To enable the preview, just activate the check-box 'Show preview of file'.
Note: To use this option JavaScript must be enabled in your browser.

GPS

The information source for GPS is the site of U.S. Coast Guard Navigation Center.

EGNOS

Information source for EGNOS is currently the ESSP with the EGNOS User Support site. Currently only the basic information is provided whether EGNOS is in operation and on which GEO PRN's.

GLONASS

The information source for GLONASS is the site of IANC - Information-analytical centre. Some of the received information are currently only available in Cyrillic!

GALILEO/Giove

Since GALILEO is not yet operational, the provided information refer to Giove (GALILEO In Orbit Validation Element).
The source of the information is ESA - European Space Agency and Dr. T.S. Kelso - CelesTrak.

top of page

---

Data

Note: The receiver data is only accessible and visible to registered users after log-in.

The Data section contains the information decoded from the GalTeC Receivers. These receiver data are available in ASCII format.

Besides the receiver data, this section contains also the Processed data that provides the results of the Reference Orbit and Clock determination as well as the calculated SISRE (Signal In Space Reference Errors) results for each GNSS satellite.

top of page

---

Data - Processed

Processed Data

In this section the results of the GalTeC Reference Orbit and Clock determination can be found in SP3 format (version C). It will be however produced only occasionally.

As default the IGS final products sp3-file will be used for the SISRE calculation (see below). These sp3 files are stored at GalTeC internally but not presented on the GalTeC site. The interested user is asked to visit the IGS site to obtain the sp3 files.

As second part the SISRE files for each GNSS satellite are listed for download. They contain the data over which the SISRE analysis was running and producing the plots and results in the Analysis section "Signal In Space".

The GALILEO Processed data menu contains the intermediate result files:

SISRE files (and SIS analysis) is currently only performed for the GNSS: GPS and GLONASS.

The detailed description of these files are found in the GalTeC ICD.

top of page

---

Data - Receiver

Note: The receiver data is only accessible and visible to registered users after log-in.

The Data - Receiver section contains the GalTeC used input data and intermediate data files in ASCII format. The result files are found directly in the Analysis section (top level after log-in).

Receiver Data

This data is available for the previous day (and older). The data collection for today is still collected until 24:00.

The 24h data is as received by the GalTeC receivers. But it has been decoded into ASCII format for further processing with the GalTeC analysis tools. The following files can be obtained directly:

The precise description can be exploited in the GalTeC ICD.

The original log of the receivers in SBF format (Septentrio Binary Format) containing much more information is achieved at GalTeC and can be requested by interested users as an additional product (please consult the GalTeC Products Catalogue located under Home -> Documents).

Receivers

Receiver Antennas

GT RX 01 - Septentio PolaRx2

The PolaRx2 receiver is configured with a GPS/EGNOS capable firmware. It is a dual frequency receiver.

For the official description please visit the related Septentrio web site. This however an next generation model of our receiver.

As the other two GalTeC receivers it is a fix installation (Monitor) at the THALES site in Stuttgart (Korntal-Münchingen resp.). As it is installed on a roof, it is literally a free sky installation. No special provision is currently undertaken for multipath avoidance, besides original antenna characteristics and receiver capabilities.

The antenna coordinates are:

In the GalTeC configuration this receiver is configured as follows:

GT RX 02 - Septentio AsteRx1

The AsteRx1 receiver is configured with a GPS/Giove-A/EGNOS capable firmware. It is a single frequency receiver. Currently it seems to be able to track Giove-B as well.

For the official description please visit the related Septentrio web site.

As the other two GalTeC receivers it is a fix installation (Monitor) at the THALES site in Stuttgart (Korntal-M�nchingen resp.). As it is installed on a roof, it is literally a free sky installation. No special provision is currently undertaken for multipath avoidance, besides original antenna characteristics and receiver capabilities.

The antenna coordinates are:

In the GalTeC configuration this receiver is configured as follows:

GT RX 03 - Septentio PolaRx3

The PolaRx3 receiver is configured with a GPS/GLONASS capable firmware. It is a dual frequency receiver (also for GLONASS).

For the official description please visit the related Septentrio web site.

As the other two GalTeC receivers it is a fix installation (Monitor) at the THALES site in Stuttgart (Korntal-Münchingen resp.). As it is installed on a roof, it is literally a free sky installation. No special provision is currently undertaken for multipath avoidance, besides original antenna characteristics and receiver capabilities.

The antenna coordinates are:

In the GalTeC configuration this receiver is configured as follows:

top of page

---

Simulation

This is the simulation and prediction section of the GalTeC. Predictions for the actual day (today) are done with the GalTeC Prediction and Simulation Tool (AVIGA Pro 2.7) based on the most recent almanacs (GPS and GLONASS) or TLE (Giove).

The structure is broken down into the single GNSS or GNSS combinations.

In the following the types of plots presented in this section are described. The predictions are computed for a grid of 1°x1° over the world or specifically for the GalTeC site Stuttgart (Germany).

Please note: A limited amount of users can apply to receive daily predictions for their individual locations (defined by Latitude, Longitude and Height over sea level inWGS84). These predictions will be delivered via e-mail. Please consult the Registration site or the GalTeC products catalogue.

GNSS prediction plots

The prediction for the selected GNSS constellation is shown for the selected day (can be as actual as today). Each simulation presents a run over the 24 hours of a day.

The basic configuration of the simulation can be found here.

"Minimum Visibility over area"

A regular grid over the considered area (world) is taken for the simulation. The minimum number of satellites in sight at each geographical grid point during the considered time period (one day) is calculated and represented on the map according to a colour scale. The colours in the map indicate the minimum number of satellites visible at each geographical location. The legend describes the correspondence of the colours to the number of satellites.

"Maximum HDOP over area"

A regular grid over the considered area (world) is taken for the simulation. The maximum Horizontal Dilution of Precision (HDOP) at each geographical grid point during the considered time period (one day) is calculated and represented on the map according to a colour scale. The colours in the map indicate the maximum HDOP at each geographical location. The legend describes the correspondence of the colours to the HDOP values.

In the following some plots for a specific user location, presently the GalTeC location (Stuttgart, Germany), are presented. As written in the introduction only a limited amount of users can apply to receive individual plots for their positions.

"Visibility of GNSS at point: NSV/time plot"

This daily plot shows the number of visible satellites at the user position (presently GalTeC, Stuttgart, Germany) as function of time.

"Visibility of GNSS at point: Elevation time plot"

This daily plot shows the elevation angles of each GNSS satellite at the user position as a function of time. Each GNSS satellite has its own colour code.

"Visibility of GNSS at point: Horizontal bar time plot"

This daily plot presents the visibility periods of the GNSS satellites as function of time at the user position. Each satellite is represented by a horizontal bar which is drawn in the plot for the periods when the satellite is visible.

"xDOP time plot"

This daily graph contains the time plots of the different Dilution of Precision (DOP) values as a function of time at the user position. The DOP factors give an indication on the expected accuracy.

GNSS prediction movie

Note: The prediction movie section is only visible for registered users!

The daily prediction movies show the instantaneous visibility characteristics as function of time. The files are Zipped AVI files which can be played by standard media player. The files must be downloaded before playing.

• Video 1: GPS visibility over area
• Video 2: GLONASS visibility over area
• Video 3: GALILEO/Giove visibility over area

top of page

---

Calendar

You can go to a defined date to request the files from this date.

Change the current date to a date in the past: Click on the left button.

top of page

---

Register to GalTeC

You can register for free to the GalTeC web site.

As a registered user you will have access to additional areas of the web site.

The following areas will be accessable after registration and after the user has logged-in.

• Data - Receiver Data
  This page contains the GalTeC used input data in ASCII format. This data is filled in with some latency with respect to the current day. See also help topic Receiver Data.
• Data - Processed Data
  The results of the GalTeC Reference Orbit and Clock determination in SP3 format (version C). It will be however produced only occasionally. And the SISRE files for each GNSS satellite. They contain the data over which the SISRE analysis was running and producing the plots and results in the Analysis section "Signal In Space". See also help topic Processed Data.
• Signal in Space result file
  The results of the Signal in Space analysis as ASCII text file can be downloaded.
• Position Accuracy result file
  The results of the Position Accuracy analysis as ASCII text file can be downloaded.
• Simulation prediction movies
  The prediction movies from the simulation for GPS, GLONASS and GALILEO will be available for download. See also help topic Simulation.

top of page

---