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Hướng dẫn bình sai GPS Huace X20 - chương VIII

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Hướng dẫn bình sai GPS Huace X20 - chương VIII

Bài gửi  conhueba_b on Sat Sep 24, 2011 1:11 am

8 Chapter VIII Known Issues
This chapter is a reference of some of the typical problems you may meet in practice.
The issues listed here are only part of those various problems occurring in the GPS
data processing. You also may meet some others.
8.1 Fundamental of Baseline Processing Settings
To meet different working patterns and precision requirements, you may need to
specify some details of the baseline computation conditions, such as types of baseline,
quality criteria, epoch sampling interval, satellite elevation angle and valid epoch, etc.
Due to the inevitable impact of the environmental factors like blocked signal, amount of
observable satellites, satellites distribution, electromagnetic disturbance, multi-path
effect and so on, it is necessary to have improvement on the baseline results by certain
means besides the abidance of the measurement operation standards, though
sometimes static measurement results are automatically processed in most cases.
Generally,
fundamental baseline processing settings include:
8.1.1 Select Proper Solution
A solution containing full integer ambiguity values is known as the
fixed-double-difference solution. A solution only containing double difference integer
ambiguity values is known as the float-double-difference solution. The
Length of
computed baselines has certain influence on the integer ambiguity resolution.
For long baselines, float solution cannot derive desirable results. Therefore triple
difference solution should be used in this case.
Different solutions should be applied on the different GPS networks on the same level
but with different baseline length. According to the GPS survey standard of China,
• Single frequency static baselines shorter than 8 km: Fixed-double-difference
138

solution should be applied on
• Baselines shorter than 30km: better solution of the fixed-double-difference solution
and float-double-difference solution. (‘Better Solution’ is a solution with minimum
mean square error, especially refers to the one that has the minimum closing Error
of asynchrony-loop checking and baseline re-checking)
• Baseline longer than 30km: Triple difference solution
• Fast positioning baseline with an observation short than 35min: qualified
fixed-double-difference solution
Observing according to the instruction of the manual, you should be able to derive
proper fixed solution for baselines shorter than 8km and baselines measured with fast
positioning. However, poor observation conditions like electromagnetic disturbance,
high-voltage wire nearby, under tree, etc, and poor satellites condition of like bad
constellation condition or large amount satellites with poor signal could lead to a bad
fixed solution. Such observation data should not be used.
8.1.2 Select Proper Parameters
Baselines can be optimized by parameters like Satellite Altitude Angle, Sampling
Interval and Valid Epoch
1. Elevation Mask
Elevation Mask is crucial to both the observation and baseline processing. A low
Elevation Mask may lead to the loss lock of satellite because of poor signal and low
Signal-to-Noise, or integer ambiguity searching failure due to the significant influence of
atmospheric refraction. However, a larger Elevation Mask may also lead to an
imperfect result because of insufficient observed satellites number and poor satellite
distribution condition.
In this software:
• The general default Elevation Mask is 10 degree, and 20, in baseline processing.

Set
Lower Elevation Mask
then re-processes baselines when
:
an Observation
satellite is very few and observation time is not long enough,
Note:
you must have stable station data, good sight condition and outer-checking,
139

synchrony-loop/asynchrony-loop checking f or example, to ensure the correctness.

Set Higher Elevation Mask
when: A failure computation occurred with long
continuous observation time, sufficient satellites and small GDOP value.
2. Sampling Interval
The Sampling rate is fairly high (fieldwork sampling interval, from every 1 second to
255 second) in most GPS receiver. However, not every data is involved in the baseline
processing; only some of them are sampled for optimized processing. High quality
carrier phase can avoid cycle slips and increasing its sampling rate up to a reasonable
level where it can detect and repair cycle slips. Therefore, you should reduce sampling
interval to a certain level under the condition of fast static workflow or short time
baseline observation.
With powerful cycle slip repairing functions, in most cases the default-sampling interval
of every 60 second can meet the requirement.
3. Invalid Epoch
You should modify the epoch of a satellite in the following situations:
•Bad satellite condition
•Frequently loss lock because of undesirable station condition or electromagnetic
disturbance
•Loss lock of low altitude angle satellite due to poor signal and low signal-to-noise
•Failure integer ambiguity searching due to fierce influence of atmospheric refraction
You can check the
details of computation
to find the cycle slips and delete satellites
frequently loss lock or have too few epochs.
8.2 Fieldwork Checking
Ensuring achieving expected adjustment precision, the fieldwork checking plays a
crucial role in the fieldwork quality control. It must be carried out in time (better be at the
140

very day) in survey-area after the observation to find out unqualified results timely then
delete, re-survey or supply-survey them if necessary.
The following checking method are often used:
8.2.1 Simultaneous Observation Baseline Checking
You can check the Variance Ratio and Mean Square Error
Generally speaking, baselines shorter than 10km with the Variance exceeding 3.0 can
meet the requirement of state/city/province Level network.
Under conditions of encryption control and lower requirements, the above criteria can
be set less strict, variance; for example, it can be set bigger than 2.0
8.2.2 Duplicate Baselines Checking
Duplicate Baselines refer to the baselines obtained by observing the same baseline in
different sessions. The difference between two baselines in different sessions should
be smaller than p times of the defined precision on their level. The difference between
any one of these baselines and the average value of all duplicate baselines should not
exceed the defined precision on their level.
8.2.3 Synchrony-closing Error and Asynchrony-closing Error
Checking
Simultaneous-loop and Asynchrony-loop refer to the closed loops obtained by
Simultaneous observation and non-Simultaneous observation respectively.
1. Asynchrony-loop
141

W
2
n
X
W
2
n
Y
W
2
n
Z
W
WWW
++
2
3
n
222
XY Z
where
n
——Number of edges in the loop
——Baseline vector length precision according to the corresponding standard
(counting with average edge length)
.
2
Simultaneous-loop
The table below shows the standards of coordinate component closing error of
simultaneous-loop and total length closing error.
Note: Table 13-1 standards: coordinate component of simultaneous-loop and total
length closing error
Level
II III IV I Grade II Grade
Error Type
coordinate component
2.0 3.0 6.0 9.0 9.0
closing error
total length closing error 3.0 5.0 10.0 15.0 15.0
(
)
Unit:
1
×
10
6
142

8.3 Adjustment Parameters and Baseline Vectors
Influence factors include: Coordinate System, Constraint Condition, Deleting baseline,
etc. For details, see below:
8.3.1 Select Coordinate System Properly
1. Standardized Systems
Although coordinate systems of the WGS-84, Beijing-54 and China-80 can be found in
the adjustment settings, correct latitude of origin (Central Meridian Projection) is still
required.
2. Customized Coordinate System (or Project Ellipsoid)
Known Parameters
Typical customized-coordinate systems are transferred from standard coordinate
systems by re-defining the Addition Constant, Central Meridian or Ellipsoid Projection
Height. You need to select these parameters.
Unknown Parameters
To set an independent coordinate system, which can’t be combined with the state
points, or of which distortion of the projection exceeds defined level, you need to use
normal ellipsoid, for example, Beijing-54. Detailed steps are:
Step 1. Set Starting Point
by using a single positioning solution of certain extreme
point on the baseline.
Step 2. Set End Point
by calculation with the following workflow:
•Measure the distance between the start point and another extreme point using
high-precision laser/infrared distance measuring instrument;
143

•Project its corrected value to pointed height(typically, average height of surveying
area);
•Set a azimuth by assumption (typically, true north);
•Then derive the coordinate of the end point.
Step 3. Set Constraint points
using the starting point and end point obtained in Step1
and 2.
Step 4.
With constraint points,
project Ellipsoid Height
using Ellipsoid parameters in
line with the previously used ones.
You can use Central Meridian of surveying area as
Latitude of Origin (Central Meridian).
Thus, distortion can be limited within required levels on one hand, and standard state
coordinate system can be combined in small-scale network, on another.
144

8.3.2 Selected Known Points Must Meet Wanted Precision
Selected Known Points should meet the following requirements:
1. Select higher-level control points from the same network in the same session.
You should try your best to select known points on higher level. In large surveying area,
you need the combined survey of some level II points. In addition, survey using level III/
IV points needs a careful checking.
The results from different networks or in different sessions have biases. Therefore, you
should select control points from the same network in the same session.
Known points of height require combined survey with points on level IV or above.
2. Known points must be distributed properly and height points need more combined
survey
Equably distributed known points, especially height points, play a crucial role in the
improvement of constraint adjustment precision. You can detect a higher-precision
abnormal height values, which will help GPS height data to meet the requirement of
standard level IV or below, using quadric surface fitting with sufficient known height
points (3-6 points for plane fitting and 6 or above or surface fitting) under a desirable
distribution condition.
3. Select Points With Better Compatibility
It would be reasonable to take three known plane points as constraint condition of
two-dimensional fixed adjustment. More combined-surveyed control points would be
used as analysis tool instead of being taken as fixed points. You can check network
adjustment quality using different known-point sets and delete incompatible start point
(For details, refer to the next section ‘Checking Adjustment Quality’).
Operationally, enter all known points > set wanted points ‘valid’ in the
Adjustment
Settings
> set others ‘invalid’.
145

8.3.3 Select Baseline Properly
1. Select Proper Computation Solution
•Select proper solutions according to the instruction in section 1.
•Select ‘Selection by Individual Baseline’ in the condition setting panel
•Select solutions for each baseline in the baseline list or on the network chart
2. Delete Baselines Containing Gross Error
In the fieldwork, you can delete baselines with unqualified re-checking length,
simultaneous-loop closing error and asynchrony-loop closing error. Further checking
can be made in the network adjustment to eliminate baselines containing gross error.
For details, refer to the next section.
3. Requirement of Baseline Chart
Baseline chart must meet the following requirements:
•No Isolated Point
You must have isolated points surveyed again to have one or more independent
baselines (an isolated point refers to a point that connects with less than two qualified
baselines).
•Independent Loops Number Must Be Controlled Within Limitation
Limitations are shown in the table below:
146

Limitations of Loops Number
Levels II III IV Grade I Grade II
Loops
6 8 10 10 10
Number
8.4 Checking Adjustment Quality
8.4.1 Requirement of Precision
For urban GPS measurement, the requirement of mean square relative error of the
baseline length:
×
1
10
Level Average
A(mm) B(
)
6
me an squa re re la ti ve er ror o f
Dist.(km)
t he w ea kest edg e
II 9 10 2 1/120000
III 5 10 5 1/80000
IV 2 10 10 1/45000
Grade 1 1 10 10 1/20000
<
Grade 2
1 10 20 1/10000
Notes:
1. A stands for fixed error of the baseline length, B stands for proportional error
1
×
10
coefficient (
)
6
2. The Minimum distance between adjacent points is 1/2-1/3 of average distance; the
Maximum distance should be 2-3 times of the average distance;
3. The mean square relative error of the baseline length should be smaller than 20mm
when baseline length smaller than 200m
8.4.2 Adjustment Checking
Adjustment checking first checks the mean square error of unit weight, mean square
length relative error, mean square error of point, error ellipsoid and so on, followed by:
147

1) Gross Error in the Free Network Baseline Data
Checking starts when the confidence level goes close 99.7% using t distribution. The
baseline vector residual derive from free adjustment should not larger than 3 times of
the distance mean square error on its level.
V
3
X
V
3
Y
V
3
Z
2) Check the known point precision (compatibility) and network distortion caused by it.
The compulsory constrained two-dimensional constraint adjustment requires a starting
data with very good internal precision, say, it is self-compatible. Otherwise, occurred
distortion of the network will spoil the precision of the GPS network.
The following factor may lead to poor-compatible known points
1) Bad precision of known points
2) Network processed using different observation methods, different starting data or
processed in different sessions may lead to inconsistent precision or even inconsistent
coordinate system. This often happens in practice, especially when independent urban
coordinate system and independent project coordinate system are used.
3) Incorrect point data
4) Incorrect point position
The difference between residual of two-dimensional constraint adjustment baseline and
gross error-free baseline in the same name should meet the following requirement:
148

dV
2
X
dV
2
Y
dV
2
Z
Otherwise, the corresponding known points would be treated as incompatible and
would be eliminated by different known points set.
8.5 GPS Network Outer Checking
•Projection Distortion
Bring the observed length on the ground factors into reference ellipsoid and calculate it
by (Height Reduce):
S
=
D
+
d
D
D

H
=

=
+
d
=
R
M
N
H
h
h
,
,
m
R
m
m
m
1
m
2
D
m
S——Length on ellipsoid
D——Observed length on ground
d
;
——Height Correction
D
H
——Average geodetic height of the observed baselines
m
h
——Average geodetic height of the observed baselines refer to geoids
m
1
h
——Average height from the geoids to the reference ellipsoid
m
2
R
——Average curvature radius of the given area
m
Meridian circle
M——
curvature radius of the reference ellipsoid
N——Prime vertical curvature radius of the reference ellipsoid
149

R
The following table shows
the values of every killometer (with assumed
=6370Km)
m
+ /
Hh h m
()()
HR
mm m
12
mm
10 1
:
600,000
:
20 1
300,000
:
50 1
100,000
:
100 1
60,000
:
150 1
40,000
:
200 1
30,000
300 1
:
20,000
400 1
:
15,000
500 1
:
12,000
1000 1
:
6000
:
2000 1
3000
:
3000 1
2000
:
4000 1
1500
Bring the ellipsoid length to the Gaussian plane by:
S
=
S
+
S
0
S

y
2
S
=
m
2
R
2
m
where,
S
——Length brought to the Gaussian plane
0
S——Length on the reference ellipsoid
y
——The average distance between S and central meridian perpendicular
m
offset on the Gaussian plane
150

R
——Average curvature radius in the given area
m
The following table shows the relative distortion of the baseline length to the
R
central meridian perpendicular offset with assumed
=6370,
m
y
S
/
S
(
)
Km
m
0
:
10 1
800,000
:
20 1
200,000
:
30 1
90,000
:
40 1
50,000
45 1
:
40,000
50 1
:
30,000
100 1
:
8000
150 1
:
36000
200 1
:
2000
:
300 1
900
151

Length distortion on the edge of the projection zone
6
3
o
o
region
region
Lat. B
y(km) Deformation y(km) Deformation
:
:
20 314057.2 1
820 156987.1 1
3300
:
:
25 302944.9 1
900 151438.9 1
3500
:
:
30 289530.3 1
980 144740.2 1
3600
:
:
35 273912.3 1
136939.9 1
4300
40 256206.4 1
:
128095.5 1
:
5000
45 236544.6 1
:
118272.2 1
:
5800
50 215073.8 1
:
107543.2 1
:
7000
55 191955.6 1
:
95989.0 1
:
8800
8.6
Compare to Total Station
8.6.1 Conceptions
Length of GPS Baseline
The distance on WGS-84 ellipsoid between two cores of two mark-stones
GPS free adjustment baseline length
Baseline length on
WGS-84 ellipsoid after the minimum constraint adjustment
GPS constrained two-dimensional adjustment baseline length
Baseline length on pointed reference ellipsoid in the Gaussian plane coordinate system,
after constrained adjustment
Electromagnetic
slope
Range
Measured distance between emission center and reflector (before projecting to the
152

reference ellipsoid but after adding the meteorology/addition constant correction) does
not equal to the slope range of the line connecting the two cores of two mark-stones. In
practice, however, measured baseline would not be longer than 20km, thus such
inequality is so small that could be ignored.
8.6.2 Check baseline length using laser/Infrared distance
measuring instrument
Besides the software solution, you can also check the control network with
Electromagnetic distancing.
NOTE: typically, two factors, GPS baseline and
Electromagnetic horizontal distance would be compared to each other directly. But
sometimes, according to relevant concepts of the baseline length mentioned above,
they are so different that a comparison shouldn’t be made, especially when the
projection distortion is big, say, when the surveying area is far away from the Central
Meridian or the average height value is large.
Only if all factors such as ellipsoid and
projection have been taken into consideration, the comparison can be made. The
measured distance of laser/infrared devices, in fact, is only 2 or 3 km. Thus,
comparisons can only be made for short/medium baselines with a higher precision
requirement of electromagnetic distancing than that of the GPS measurement. For X20
(
)
receiver (marked precision is ±
5mm+2ppm
), a high precision (better than ±
(3mm+ 2ppm)) electromagnetic distancing is needed.
Checking Methods:
1. Project the GPS baseline to the average height plane of the
electromagnetic
horizontal distance and compare it to the horizontal distance. Since it is possibly unable
to derive the height anomaly from the WGS-84 ellipsoid to height plane, the GPS
baseline length is inverse-projected to the average geodetic height of the two cores of a
pair of marlstones.
2. Project electromagnetic horizontal distance to the Gaussian plane and compare it to
the GPS constrained-two-dimensional adjusted baseline length. Using the GPS
network coordinate, Laser/Infrared-measured horizontal distance can be projected to
the Gaussian plane precisely. If influence of the projection is minimized due to a
relatively small deformation of the surveying area, or the properly selected projection
153


parameters, then such horizontal distance can be directly compared to the GPS
two-dimensional constrained adjusted baseline length.
In fact, the precision of them cannot be exactly the same due to many kinds of factors,
such as measurement precision and the precision of used equation. The difference
depends on the precision of the network.
8.6.3 Compare-survey to Total Station
Distance
of the baseline vectors is actually the GPS slope distance. It is comparable to
the slope distance measured by a total station (after temperature correction, humidity
correction and atmospheric refraction correction) when the height of the device is taken
into account.
GPS Slope
115.
GPS Slope Distance
Since the ground is treated as a plane when a total station calculates the horizational
distance using Pythagorean Theorem. However, the ground is actually a curved
surface and the ‘distance’ refers to the chord length on the earth surface. Thus, this two
‘distance’ are different.
In this software, both slope distance and horizontal distance are available on the
Baseline Attribute
dialog-box where listed horizontal distance is neither chord length
nor horizontal distance from the total station, it is a derived value by calculating the
baseline slope distance and difference of the baseline heights together using the
Pythagorean theorem.
154


116.
Fixed Solution
That is to say, for a relatively short baseline, the difference among chord length on
ellipsoid, horizontal distance of the total station and horizontal distance of baseline
attribute would be comparatively small and the comparability would come out too.
Nevertheless, any of these three distances is different from the projective coordinate
(plane coordinate) inverse-calculated horizontal distance. What you have from the
geodetic survey is the projective coordinate. Beside for the projective coordinate, there
is also inverse-calculated horizontal distance based on the projective coordinate in the
GPS adjustment result. It is not correct to compare this distance with that one of total
station!
To do mutual check between the total station precision and GPS receiver, you can first
compare the two distances. However, if you want to use the last one, make sure that
the projection correct has been made first.
155

Appendix A Terms
International GPS Service (IGS):
An initiative of the International Association of
Geodesy, as well as several other scientific organizations, that was established as a
service at the beginning of 1994. The IGS comprises of many component (of) civilian
agencies working cooperatively to operate a permanent global GPS tracking network,
to analyze the recorded data and to disseminate the results to users via the Internet.
The range of "products" of the IGS include precise post-mission GPS satellite
ephemeredes, tracking station coordinates, earth orientation parameters, satellite clock
corrections, troposphere and ionosphere models. Although these were originally
intended for the geodetic community as an aid to carrying out precise surveys for
monitoring crystal motion, the range of users has since expanded dramatically. In
addition, the utility of the IGS is such that it is vital to the definition and maintenance of
the International Terrestrial Reference System (and its various "frame realizations"
ITRF92, ITRF94, ITRF96, etc.).
Ambiguity:
Carrier phase measurements can only be made in relation to a cycle or
wavelength of the L1 or L2 carrier waves because it is impossible to discriminate
different carrier cycles (they are all "sine waves" if one ignores the modulated
messages and PRN codes). Those receivers intended for carrier phase-based
positioning might make integrated carrier phase measurements. In this case, the
change in receiver-satellite distance can be measured by counting the number of the
whole wavelengths since initial signal lock-on and adding the instantaneous fractional
phase measurement. However, such a measurement is a biased range or distance
measurement because the initial number of the whole (integer) wavelengths in the
receiver-satellite distance is unknown. This unknown value is referred to as the
"ambiguity". It is different for the different satellites, and different for the L1 and L2
measurements. It is, however, a constant if signal tracking continues uninterrupted
through an observation session. If there is signal blockage, then a "cycle slip" occurs,
causing the new ambiguity after the cycle slip to be different from the value before.
Cycle slip repair therefore restores the continuity of carrier cycle counts and ensures
that there is only one ambiguity for each satellite-receiver pair.
Baseline:
A Baseline consists of a pair of stations for which simultaneous GPS data
have been collected. Mathematically expressed as a vector of coordinate differences
between the two stations, or an expression of the coordinates of one station with
156

respect to the other (whose coordinates are assumed known, and is typically referred
to as a "Base" or "Reference" Station).
Cycle Slip:
A discontinuity of an integer number of cycles in the measured (integrated)
carrier phase resulting from a temporary loss-of-lock in the carrier-tracking loop of a
GPS receiver. This corrupts the carrier phase measurement, causing the unknown
Ambiguity value to be different after the cycle slip compared with its value before the
slip. It must be "repaired" (the unknown number of "missing" cycles determined and the
carrier observation subsequent to the cycle slip all corrected by this amount) before the
phase data is processed in double-differenced observables for GPS Surveying
techniques.
Carrier:
A radio wave having at least one characteristic (e.g., frequency, amplitude,
phase) that can be varied from a known reference value by modulation. In the case of
GPS, there are two transmitted carrier waves: (a) L1 at 1575.42MHz, (b) L2 at
1227.60MHz, modulated by the Navigation Message (both L1 and L2), the P-Code
(both L1 and L2) and the C/A-Code (L1).
C/A-Code:
The standard (Clear/Acquisition) GPS PRN code, also known as the
Civilian Code or S-Code. Only modulated on the L1 carrier. Used by the GPS receiver
to acquire and decode the L1 satellite signal, and from which the L1 pseudo-range
measurement is made. Frequency: 1.023MHz, Code Repeat Cycle: 1ms
Single Difference Survey
(two receivers) the phase difference of the signals from a
pair of receivers that observation of the same satellites simultaneously.
Double Difference Survey
(two-satellite-two-receiver combinations) : A data
processing procedure by which the pseudo-range or carrier phase measurements
made simultaneously by two GPS receivers are combined so that, for any
measurement epoch, the observations from one receiver to two satellites are
subtracted from each other (in a so-called "between-satellite single-difference") to
remove that receiver's clock error (or bias). (Similarly for the other receiver's
observations to the same two satellites.) Then the two single-differences are subtracted
to eliminate the satellite clock errors as well as to reduce significantly the effect of
unmodelled atmospheric biases and orbit errors. (The order may be reversed, i.e., take
"between-receiver single-differences" to each satellite in turn, and then difference
157

between the single-differences.)
Triple-Difference
(two-satellite-two-receiver and two-epoch): A linear combination of
the Double-Difference carrier phase observables by which the cycle ambiguity
parameters can be eliminated and which is less affected by unrepaired cycle slips than
the Double-Differences. A Triple-Differenced observable is created by differencing two
consecutive Double-Differences (the same pair of receivers and the same pair of
satellites, but separated in time). A useful observable for obtaining approximate
baseline solutions or for detecting cycle slips in the Double-Differenced observables.
Differential Positioning:
Also known as Relative Positioning. The precise
measurement of the relative positions of two receivers tracking the same GPS signals.
Maybe considered synonymous with DGPS, or the term may be reserved for the more
precise carrier phase-based baseline determination technique associated with GPS
Surveying.
Geometric dilution of precision:
An indicator of the satellite geometry for a unique
constellation of the satellites used to determine a position. The positions tagged with a
higher DOP value generally constitute poorer measurement results than those tagged
with lower DOP.
()
DOP trQ Q
1
=
T
Equation:
There is a variety of DOP indicators, such as GDOP (Geometric DOP), PDOP (Position
DOP), HDOP (Horizontal DOP), VDOP (Vertical DOP), etc.
Kinematics Positioning:
Kinematics Positioning refers to the applications in which the
position of a non-stationary object (vehicle, ship, and aircraft) is determined.
Ephemeris:
The file of the values from which a satellite's position and velocity (the
so-called "satellite state vector") at any instant in time can be obtained. The "Broadcast
Ephemeris (or Ephemeredes)" for a satellite are the predictions of the current satellite
position and velocity determined by the Master Control Station, uploaded by the Control
Segment to the GPS satellites, and transmitted to the user receiver in the Data
Message. "Precise Ephemeris (or Ephemeredes)" are post-processed values derived
by, for example, the International GPS Service (IGS), and available to users
158

post-mission via the Internet.
()
1 11
()
f a ab e
= =
2
Flattening:
, where
a
denotes semi-major axis and
b
denotes semi-minor axis,
e
denotes eccentricity
Geoids:
The fundamental surface in Geodesy. It is defined as the equipotent surface of
the gravity field that most closely approximates the Mean Sea Level. (The MSL
deviates from the Geoids surface by 1-2 meters due to the Sea Surface Topography
caused by wind-driven or geotropic currents.) The Geoids is the Vertical Datum surface
both from a mathematical viewpoint (i.e., the sum of the Optometric Height and the
Geoids Height equals the Ellipsoidal Height of a point), as well as in practice by making
the land height system synonymous with the "height above MSL". The models of the
Geoids Height have been determined from the combined processing of the
satellite-derived potential models, surface gravity observations and the ocean gravity
anomalies derived from Satellite Altimetry. Their accuracy may range from a few
meters in the open ocean areas, down to the few decimeter level in land areas where
there is a good coverage of the surface gravity.
Ionosphere delay
: The Ionosphere Delay on GPS signals is frequency-dependent and
hence affects the L1 and L2 signals by a different amount (unlike that within the
Troposphere).
L-band
: 390-1550MHz radio frequency
Multi-path error
: The errors caused by the interference of a signal that has reached
the receiver antenna by two or more different paths. This is usually caused by one path
being bounced or reflected. The impact on a pseudo-range measurement may be up to
a few meters. In the case of carrier phase, this is (of the order of) a few centimeters.
Observing session
: A session in which the GPS data are simultaneously received by
more than two receivers.
Pseudo range
: A distance measurement based on the correlation of a satellite's
transmitted code (may be the C/A-Code or the encrypted P-Code) and the local
159

receiver's reference code (for that PRN satellite number), that has not been corrected
for errors in synchronization between the transmitter's clock and the receiver's clock.
Hence, a pseudo-range measurement is a time-error biased distance measurement.
The precision of the measurement is a function of the resolution of the code, hence
C/A-Code pseudo-range measurements may have a "noise" at the few meter level for
standard GPS receivers (and at the sub-meter precision level in the case of so-called
"narrow correlation" GPS receivers).
Receiver channel
Receive and track two signals of satellite.
Satellite configuration:
Configuration status in a given session for a given user or a
users group.
Static position:
The measurement that does not consider the receivers’ moving
locations.
Universal time (UT):
referred to, now colloquially, as "Greenwich Mean Time"
(abbreviated
GMT
). The two terms are often used loosely to refer to time kept on the
Greenwich meridian (longitude zero), five hours ahead of Eastern Standard Time.
Times given in UT are usually given in terms of a 24-hour clock. Thus, 14:42 (often
written simply 1442) is 2:42 p.m., and 21:17 (2117) is 9:17 p.m. Sometimes a Z is
appended to a time to indicate UT, as in 0935Z.
UT0
is the rotational time of a particular place of observation. It is observed as the
diurnal motion of stars or extraterrestrial radio sources, and from ranging
observations of the Moon and artificial Earth satellites. If the geographic longitude
of the observatory with respect to Greenwich is known, a simple subtraction yields
UT0. However, because of polar motion, the geographic position of any place on
Earth varies, and different observatories will find a different value for UT0 at the
same moment. UT0 was kept by pendulum clocks but there are errors in UT0 due
to polar motion. When UT0 is corrected for the shift in longitude of the observing
station caused by the polar motion, the time scale UT1 is obtained.
UT1
is computed by correcting UT0 for the effect of polar motion on the longitude
160

of the observing site. UT1 is the same everywhere on Earth, and defines the true
rotation angle of the Earth with respect to a fixed frame of reference. Since the
rotational speed of the earth is not uniform, UT1 has an uncertainty of plus or
minus 3 milliseconds per day.
UT2
is rarely used anymore and is mostly of historic interest. It is a smoothed
version of UT1. UT1 has irregular as well as periodic variations.
UTC
(Coordinated Universal Time) is the international standard on which civil time
is based. It is measured with atomic clocks, and is kept within 0.9 seconds of UT1
by the introduction of one-second steps to UTC.
Sampling
: Obtaining values of a continuous variable with a periodical interval.
Observation Condition
: the distribution and moving trace of satellite constellation.
161

Appendix B: Julian Date Table
Date Jan. Feb. Mar. Apr. May. Jun. Jul. Aug. Sep. Oct. Nov. Dec.
1 1 32 60 91 121 152 182 213 244 274 305 335
2 2 33 61 92 122 153 183 214 245 275 306 336
3 3 34 62 93 123 154 184 215 246 276 307 337
4 4 35 63 94 124 155 185 216 247 277 308 338
5 5 36 64 95 125 156 186 217 248 278 309 339
6 6 37 65 96 126 157 187 218 249 279 310 340
7 7 38 66 97 127 158 188 219 250 280 311 341
8 8 39 67 98 128 159 189 220 251 281 312 342
9 9 40 68 99 129 160 190 221 252 282 313 343
10 10 41 69 100 130 161 191 222 253 283 314 344
11 11 42 70 101 131 162 192 223 254 284 315 345
12 12 43 71 102 132 163 193 224 255 285 316 346
13 13 44 72 103 133 164 194 225 256 286 317 347
14 14 45 73 104 134 165 195 226 257 287 318 348
15 15 46 74 105 135 166 196 227 258 288 319 349
16 16 47 75 106 136 167 197 228 259 289 320 350
17 17 48 76 107 137 168 198 229 260 290 321 351
18 18 49 77 108 138 169 199 230 261 291 322 352
19 19 50 78 109 139 170 200 231 262 292 323 353
20 20 51 79 110 140 171 201 232 263 293 324 354
21 21 52 80 111 141 172 202 233 264 294 325 355
22 22 53 81 112 142 173 203 234 265 295 326 356
23 23 54 82 113 143 174 204 235 266 296 327 357
24 24 55 83 114 144 175 205 236 267 297 328 358
25 25 56 84 115 145 176 206 237 268 298 329 359
26 26 57 85 116 146 177 207 238 269 299 330 360
27 27 58 86 117 147 178 208 239 270 300 331 361
28 28 59 87 118 148 179 209 240 271 301 332 362
29 29 88 119 149 180 210 241 272 302 333 363
30 30 89 120 150 181 211 242 273 303 334 364
31 31 90 151 212 243 304 365

NOTE:
1. There are 29 days in February during a leap year. Thus, Julian date of Feb. 29 is 60
and each value of the others is larger than corresponding value in above table by 1.
2. Leap years: there is a leap year, every year divisible by four except for years, which
are both divisible by 100 and not divisible by 400.
Therefore, 1992,1996,2000,2004
and 2008… are leap years.
163

Appendix C Instruction of RINEX
1. Observation Data File
Each file consists of a header section and a data section. There are shown in Table
C.1 and Table C.2 respectively. There are several definitions of the terms:
Time System Identifier
The original RINEX Version 2 needed one major supplement, the explicit definition of
the time system:
The GLONASS is running on UTC (or, more precisely, the GLONASS system time
linked to UTC (SU)), i.e. the time tags are given in the UTC and not GPS time. In order
to remove possible misunderstandings and ambiguities, the header records the “TIME
OF FIRST OBS” and (if present) “TIME OF LAST OBS” in GLONASS and GPS
observation files _can_. In mixed GLONASS/GPS observation files _must_ contain a
time system identifier defining the system that all time tags in the file are referring to:
“GPS” to identify GPS time, “GLO” to identify the GLONASS UTC time system. Pure
GPS files default to GPS and pure GLONASS files default to GLO.
Hence, the two possible time tags differ by the current number of leap seconds.
In order to have the current number of leap seconds available we recommend
including a LEAP SECOND line into the RINEX header.
If there are known non-integer biases between the ``GPS receiver clock'' and
``GLONASS receiver clock'' in the same receiver, they should be applied. In this case
the respective code and phase observations have to be corrected, too (c * bias if
expressed in meters).
Unknown biases will have to be solved for during the post processing
The small differences (modulo 1 second) between GLONASS system time, UTC(SU),
UTC(USNO) and GPS system time have to be dealt with during the post-processing
and not before the RINEX conversion. It may also be necessary to solve for the
164

remaining differences during the post-processing.
Pseudo-range Definition
The pseudo-range (code) measurement is defined to be equivalent to the difference of
the time of reception (expressed in the time frame of the receiver) and the time of the
transmission (expressed in the time frame of the satellite) of a distinct satellite signal.
If a mixed-mode, GPS/GLONASS receiver refers to all the pseudo-range observations
to one receiver clock only,
•the raw GLONASS pseudo-ranges will show the current number of leap seconds
between GPS time and GLONASS time if the receiver clock is running in the GPS time
frame
•the raw GPS pseudo-ranges will show the negative number of leap seconds between
GPS time and GLONASS time if the receiver clock is running in the GLONASS time
frame
PHASE:
The phase is the carrier-phase measured in the whole cycles at both L1 and L2. The
half-cycles measured by squaring-type receivers must be converted to whole cycles
and flagged by the wavelength factor in the header section.
The phase changes in the same sense as the range (negative Doppler). The phase
observations between epochs must be connected by including the integer number of
the cycles. The phase observations will not contain any systematic drifts from
intentional offsets of the reference oscillators.
The observables are not corrected for external effects like atmospheric refraction,
satellite clock offsets, etc.
If the receiver or the converter software adjusts the measurements using the
real-time-derived receiver clock offsets dT(r), the consistency of the 3 quantities phase
/ pseudo-range / epoch must be maintained, i.e. the receiver clock correction should
be applied to all 3 observables:
165

(corr)
=
(recv)
-

T (corr)
=
T (recv)
-
L1 (corr)
=
L1 (recv)
-F
×
,
Doppler:
Doppler values
D1
D2 (Hz) can be recorded using certain processing
software.
TABLE C.1 OBSERVATION DATA FILE - HEADER DESCRIPTION
HEADER LABEL
DESCRIPTION FORMAT
~
61
80
RINEX VERSION/TYPE Format version (2)
16
,
14X
File type O——Observation Date
A1
,
19X
,
Positioning System G——GPS
A1
19X
R——GLONASS
M——MIXED
,
PGM / RUN BY / DATE Name of the program creating the current file
A20
Name of the agency creating the current file
A20
,
Date of the file creation
A20
COMMENT Comment Line(s) A60
MARKER NAME Name of the antenna marker A60
MARKER NUMBER Number of the antenna marker A20
,
OBSERVER / AGENCY Name of the observer / agency A20
A40
REC# / TYPE / VERS Receiver number, type, version 3A20
ANT# / TYPE Ant number and type 2A20
APPROX POSITION
Approximate marker position (WGS84) 3F14.4
XYZ
ANTENNA: DELTA
Antenna height: H
3F14.4
H/E/N
Eccentricities of the antenna center relative to
the maker to the east: E
Eccentricities of the antenna center relative to
the maker to the west: N
WAVELENGTH FACT
Wavelength factors for L1 will L2
2I6
L1/2
1: Full cycle ambiguities
2: Half cycle ambiguities (squaring)
0: ( L1) Single frequency instrument
Number of satellites to follow in the list
I6
166

Default wavelength factors.
7(3X,A1,12)
Max 7.
If more than 7 satellites: Repeat record.
List of the PRNS (satellite numbers)
# / TYPES OF OBSERV Number of the different observation types
I6
Observation types:
9(4X,A2)
L1, L2:L1, L2 Phase measurements (cycle)
C1: Pseudo-range using C/A-Code on L1 (m)
P1, P2: L1,L2 P Pseudo-range using P-Code
on L1,L2(m)
D1,D2: Doppler frequency on L1 and L2 (Hz)
T1,T2: Transit Integrated Doppler(cycle)
After AS, L2 and P2 would be changed
INTERVAL Observation interval (s) I6
(
,
TIME OF FIRST OBS Time of the first observation record
year,
5I6
F12.6
)
month, day, hour, min, sec
6X, A3
Time SYS: GPS=GPS Time SYS
GLO=UTC Time SYS
GPS/GLONASS default value:
GPS=pure GPS file
GLO=pure GLONASSfile
(
,
TIME OF LAST OBS
Time of the last observation record
year,
5I6
F12.6
month, day, hour, min, sec
)
6X,A3
Time SYS: GPS=GPS Time SYS
GLO=UTC Time SYS
GPS/GLONASS default value:
GPS=pure GPS file
GLO=pure GLONASSfile
LEAP SECONDS sec. slips from Jan. 6
, 1980 in
I6
th
GPS/GLONASS
#OF SATELLITES Number of Satellites in the file I6
PRN / # OF OBS PRN (sat.number), number of observations
3X,A1,I2,9I6
,
If more than 9 satellites: Repeat record.
6X
9I6
END OF HEADER Last record in the header section 60X
167

Table C.2 OBSERVATION DATA FILE - DATA RECORD DESCRIPTION
Obs. Record DESCRIPTION
,
EPOCH /SAT
Epoch :year, month, day, hour, min, sec
5I3
F11.7
Or
Epoch flag 0
:
OK
I3,
EVENT FLAG
1
:
power failure between
previous and current epoch
:
1
Event flag
I3
Number of satellites in the current
I2(A1,I2)
epoch:
F12.9
,
If more than 12 satellites
Continued in
32X,12(A1,I2)
(
,
)
the next line with n
A1
I2
Receiver clock offset
(
s
)
:
If EVENT FLAG record Epoch flag>1
:
Event Flag
2: start moving antenna
3: new site occupation (end on kinem.
data) (at least MARKER NAME record
follows)
4: header information follows
5: external event (epoch is significant)
6: cycle slip records follow to optionally
report detected will repaired cycle slips
"Number of satellites" contains number
of records to follow (0 for event flags
2,5)
m
OBSERVATIONS Observation
(F14.3,I1,I1)
LLI
Signal strength
This record is repeated for each satellite
given in EPOCH/SAT – record.
If more than 5 observation types (=80
char): Continue observations in next
record.
:
Observations
Phase : Units in whole cycles of carrier
168

Code : Units in meters
Missing observations
:
(
~
)
LLI
Loss of lock indicator
0
7
Ok
Default
AS
:
Signal strength
:
1
Minimum strength
5
:
Medium strength
:
9
Maximum strength
:
0
Ignore
2. Navigation Message File
If the data from more than one receiver has to be exchanged it would not be
economical to include the identical satellite messages collected by the different
receivers several times. Therefore, the Navigation Message File from one receiver
may be exchanged or a composite Navigation Message File created containing
non-redundant information from several receivers in order to make the most complete
file. Each file consists of a header section and a data section. There are shown in
Table 2.2.3 and Table 2.2.4 respectively.
TABLE 2.2.3
HEADER LABEL
DESCRIPTION
FORMAT
Columns
(
61
~
)
80
Format version
RINEX VERSION /
(
2
)
I6
,
14X
,
File type ('N' for Navigation data)
,
TYPE
A1
19X
Name of program creating current file
PGM / RUN BY /
A20
Name of the agency creating current
DATE
A20
file
A20
Date of the file creation
Comment line(s)
COMMENT
A60
Ionosphere parameters A0-A3
TON ALPHA
,
4D12.4
2X
Ionosphere parameters
ION BETA
,
4D12.4
B0—B3 2X
Almanac parameters to compute for
:
DELTA-UTC
169

the time in the UTC
,
A0,A1,T,W
3X
2D19.12
terms of polynomial
,
:
2I9
A0
A1
reference time for UTC data
T
:
UTC reference week number
W
:
Delta time due to leap seconds
LEAP SECONDS
I6
Last record in the header section.
END OF HEADER
60X
GPS NAVIGATION MESSAGE FILE - DATA RECORD DESCRIPTION
TABLE 2.2.4
OBS. RECORD
DESCRIPTION
FORMAT
Satellite PRN number
,
PRN /EPOCH / SV
5I3
F11.7
Epoch: Toc - Time of Clock
CLK
I3,
year (2 digits)
month
day
I3
hour
I2(A1,I2)
minute
F12.9
second
32X,12(A1,I2)
SV clock bias
(
S
)
SV clock drift
(
)
s/s
SV clock drift rate
(
)
s/s
2
BROADCAST
IODE Issue of Data, Ephemeris
3X
,
4D19.12
(m)
ORBIT-1
Crs
n rad/s
)
M
(
rad
)
0
(
)
BROADCAST
Cuc
rad
ORBIT-2
e
Eccentricity
Cus
(
rad
)
A
m
(
)
BROADCAST
Toe Time of the Ephemeris
3X,4D19.12
(
)
ORBIT-3
Cic
rad
(
rad
)
Cis
(
rad
)
(
)
BROADCAST
I
rad
3X,4D19.12
ORBIT-4
Crc (m)
(
rad
)
dot (rad/m)
170

BROADCAST
Idot (rad/s)
3X,4D19.12
ORBIT-5
L2
(
)
GPS Week
TOE
L2 P data flag
(
)
BROADCAST
SV accuracy
m
3X,4D19.12
ORBIT-6
SV health
(
MSB
)
TGD
(
s
)
IDOC Issue of Data, Clock
BROADCAST
Transmission time of the message
3X,4D19.12
(
ORBIT-6
sec of GPS week, derived e.g. from
)
Z-count in Hand Over Word (HOW)
Appendix D SP3 Precise Ephemeris Format
# @(# ) sp3 1. 3 03/ 08 / 95
#a V19 93 1 29 0 0 0. 00 00 000 0 9 6 d IT R 91 F I T JPL
## 68 1 43 20 00. 00 00 000 0 9 00 .0 00 000 00 4 90 16 0. 0 000 00 000 00 00
+ 19 1 2 3 12 13 14 15 1 6 17 1 8 19 2 0 21 2 3 24 2 5 26
+ 2 7 28 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
+ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
+ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
+ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
+ + 10 1 0 10 1 0 10 1 0 10 1 0 10 1 0 10 1 0 10 1 0 10 1 0 10
+ + 10 11 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
+ + 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
+ + 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
+ + 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
%c cc cc ccc ccc cccc cccc cccc c ccc cc ccc ccc cc cc ccc c cccc
%c cc cc ccc ccc cccc cccc cccc c ccc cc ccc ccc cc cc ccc c cccc
%f 0 .0 00 000 0 0 .0 00 00 000 0 0 .0 00 000 00 000 0. 00 00 00 000 00 000 0
%f 0 .0 00 000 0 0 .0 00 00 000 0 0 .0 00 000 00 000 0. 00 00 00 000 00 000 0
%i 0 0 0 0 0 0 0 0 0
171

%i 0 0 0 0 0 0 0 0 0
/ * CC CCC CC CC CCC CC CC CCC CC CC CCC CC CC CCC CC CCC CC CC CCC CC CCC CC CC CCC
/ * CC CCC CC CC CCC CC CC CCC CC CC CCC CC CC CCC CC CCC CC CC CCC CC CCC CC CC CCC
/ * CC CCC CC CC CCC CC CC CCC CC CC CCC CC CC CCC CC CCC CC CC CCC CC CCC CC CC CCC
/ * CC CCC CC CC CCC CC CC CCC CC CC CCC CC CC CCC CC CCC CC CC CCC CC CCC CC CC CCC
* 1 99 3 1 2 9 0 0 0 .0 00 000 00
P 1 147 22 .6 38 510 64 64 .3 19 150 - 210 20 .8 448 10 -8. 05 92 18
V 1 -119 6. 62 880 0 2 69 50. 02 25 00 750 2. 27 71 00 0. 00 00 00
P 2 -2 402 3. 15 53 00 -11 843 .5 63 99 0 -16 75 .6 47 210 -1 0. 81 396 4
V 2 -76 9. 15 270 0 -3 24 7. 50 800 0 3 125 5. 02 33 00 0. 00 00 00
P 3 207 4. 55 54 20 190 25 .9 98 840 17 92 8. 366 12 0 -4 30. 8 590 48
V 3 -68 73. 9 323 00 22 421 .6 64 200 -231 47 .5 29 600 0 .0 000 00
P 12 -623 6. 32 55 80 131 53 .2 712 60 -2 19 64. 1 000 40 -10 8. 94 573 7
V 12 -2 73 84. 9 171 00 68 05. 63 28 00 123 37 .7 28 800 0 .0 000 00
P 13 -1 330 6. 85 71 00 479 0. 06 211 0 -223 60 .5 23 490 62 8. 24 02 51
V 13 97 39. 7 386 00 -2 68 64. 61 24 00 -11 662 . 222 50 0 0 .0 00 000
. . . .
. . . .
. . . .
P 27 -1 935 0. 82 02 60 -400 3. 11119 0 1 758 2. 69 07 90 14. 6 514 64
V 27 19 491 . 879 10 0 -1199 0. 04 24 00 1 81 56 .9 044 00 0. 00 00 00
P 28 133 16 .3 78 500 -139 59 .6 444 90 18 317 . 660 94 0 5 2. 52 000 5
V 28 25 8. 24 640 0 2 33 16. 4 208 00 172 08 .9 28 500 0 .0 00 000
EO F
SP3 L IN E 1
col 1 symbol #
col 2 version id a
col 3 P/V mode flag V
co l 4- 7 yea r st a rt 1 993
co l 9-1 0 mont h st art _1
co l 12- 13 d ay of mon t h sta rt 29
col 15-16 hour start _0
co l 18- 19 m inu t e sta rt _ 0
co l 21-3 1 s econ d st art _0. 0 000 00 00
co l 33-3 9 n umb er of ep och s _ ___ _9 6
co l 41- 45 d at a u sed _ __ _d
172

co l 47-5 1 c oor din at e syst em IT R 91
co l 53- 55 o rbi t t ype FI T
co l 57-6 0 a ge ncy na me _ JPL
SP3 L IN E 2
col 1- 2 symbols ##
col 4- 7 GPS week _681
co l 9-2 3 secon ds of we ek 43 200 0. 00 00 000 0
co l 25- 38 e po ch in te rval _ _9 00. 0 000 00 00
co l 40- 44 m od. ju lia n da y st ar t 4 90 16
co l 46- 60 f ra cti on al d ay 0. 00 000 00 000 00 0
SP3 L IN E 3
col 1- 2 symbols +_
co l 5- 6 nu mbe r o f sa te lli te s 1 9
co l 10- 12 s at # 1 id __1
co l 13- 15 s at # 2 id __2
.
.
.
co l 58- 60 s at # 17 i d _2 6
SP3 L IN ES 4-7
col 1- 2 symbols +_
co l 10- 12 s at # 18 (35 ,5 2, 69) i d _ 27
co l 13- 15 s at # 19 (36 ,5 3, 70) i d _ 28
.
.
.
co l 58- 60 s at # 34 (51 ,6 8, 85) i d _ _0
SP3 L IN ES 8-1 2
col 1- 2 symbols ++
co l 10- 12 s at # 1(1 8, 35 ,5 2, 69 ) a cc _1 0
co l 13- 15 s at # 2(1 9, 36 ,5 3, 70 ) a cc _1 0
.
.
.
173

co l 58- 60 s at # 17 (34, 5 1, 68, 8 5) acc _1 0
SP3 L IN ES 13 -14
col 1- 2 symbols %c
col 4- 5 2 characters cc
col 7- 8 2 characters cc
co l 10-1 2 3 char act ers ccc
co l 14-1 6 3 char act ers ccc
co l 18-2 1 4 char act ers cccc
co l 23-2 6 4 char act ers cccc
co l 28-3 1 4 char act ers cccc
co l 33-3 6 4 char act ers cccc
co l 38-4 2 5 char act ers ccccc
co l 44-4 8 5 char act ers ccccc
co l 50-5 4 5 char act ers ccccc
co l 56-6 0 5 char act ers ccccc
SP3 L IN ES 15 -16
col 1- 2 symbols %f
co l 4-1 3 1 0-co lu mn f loa t _0 . 000 00 00
co l 15- 26 1 2-co lu mn f loa t _0 .0 00 00 000 0
co l 28- 41 1 4-co lu mn f loa t _0 .0 00 00 000 00 0
co l 43- 60 1 8-co lu mn f loa t _0 .0 00 00 000 00 000 00
SP3 L IN ES 17 -18
col 1- 2 symbols %i
co l 4- 7 4-co lu mn int __ _0
co l 9-1 2 4 -col umn i nt ___ 0
co l 14-1 7 4 -col umn i nt ___ 0
co l 19-2 2 4 -col umn i nt ___ 0
co l 24-2 9 6 -col umn i nt ___ __ 0
co l 31-3 6 6 -col umn i nt ___ __ 0
co l 38-4 3 6 -col umn i nt ___ __ 0
co l 45-5 0 6 -col umn i nt ___ __ 0
co l 52-6 0 9 -col umn i nt ___ __ __ _0
SP3 L IN ES 19 -22
col 1- 2 symbols /*
174

col 4-60 comment CC...CC
SP3 L IN E 23 (e poch hea de r re cord )
col 1- 2 symbols *_
co l 4- 7 yea r st a rt 1 993
co l 9-1 0 mont h st art _1
co l 12- 13 d ay of mon t h sta rt 29
col 15-16 hour start _0
co l 18- 19 m inu t e sta rt _ 0
co l 21-3 1 s econ d st art _0. 0 000 00 00
SP3 L IN E 24 (p osit io n an d clo ck record )
col 1 symbol P
col 2- 4 satellite id __1
co l 5-1 8 x-coo rdin at e (km) __ 147 22 .6 38 510
co l 19-3 2 y-coo rdin at e (km) ___ 64 64 .3 191 50
co l 33-4 6 z -coo rdin at e (km) _-2 102 0. 84 48 10
co l 47-6 0 c lock (mi crose c) _ __ __-8 .0 59 21 8
SP3 L IN E 25 (ve loci t y a nd cl ock reco rd)
col 1 symbol V
col 2- 4 satellite id __1
co l 5-1 8 x-dot (de cim/ sec) __ -119 6. 62 880 0
co l 19- 32 y-dot (de cim/ sec) __ 26 950 . 022 50 0
co l 33- 46 z -dot (de cim/ sec) __ _7 502 . 277 10 0
co l 47-6 0 c l rat e (10 e-4 mse c/ sec) __ __ __0 .0 00 000
.
.
.
SP3 L IN E 22+ nu mep s*(n umsa ts+ 1)+ 1 (la st li ne )
col 1- 3 symbols EOF
175

Appendix E YUMA Ephemeris Format
ID:
PRN of the SVN
Health:
000=usable
Eccentricity:
This shows the amount of the orbit deviation from the circular
(orbit). It is the distance between the foci divided by the length of the semi-major
axis (our orbits are very circular).
Time of Applicability:
The number of seconds in the orbit when the almanac
was generated. Kind of a time tag.
Orbital Inclination:
The angle to which the SV orbit meets the equator (GPS is at
approx. 55 degrees). Roughly, the SV's orbit will not rise above approx. 55 degrees
latitude. The number is part of an equation: #= pi/1 80 = the true inclination.
Rate of Right Ascension:
Rate of change in the measurement of the angle of
right ascension as defined in the Right Ascension mnemonic.
Square Root of Semi - Major Axis:
This is defined as the measurement from the
center of the orbit to either the point of apogee or the point of perigee.
Right Ascension at Time of Almanac (TOA):
Right Ascensions is an angular
measurement from the vernal equinox (omega (0)).
Argument of Perigee:
An angular measurement along the orbital path measured
from the ascending node to the point of perigee, measured in the direction of the
SV's motion.
Mean Anomaly:
Angle (arc) traveled past the longitude of ascending the node
(value= 0-1 80 degrees or 0-negative 1 80 degrees). If the value exceeds 1 80
degrees, subtract 360 degrees to find the mean anomaly. When the SV has passed
perigee and heading towards apogee, the mean anomaly is positive. After the point
of apogee, the mean anomaly value will be negative to the point of perigee.
Af(0):
SV clock bias in seconds
Af(1):
SV clock Drift in second per second
week:
GPS week (0000-1 024), every 7 days since 6 Jan 1 980/0000z
176

Postscript
1. Software Using Environment
The Software introduced in this manual is running under following environment with
minimum 32MB RAM and 200MB memory on your hard disc.
,
,
,
,
Microsoft ® Windows 95
97
98
SE
ME
Microsoft ® Windows NT Server Pack 4 and later
Microsoft ® Windows 2000
2. Copyright & Trademark
2003-2005, HuaceNav. All rights reserved.
©
HuaceNav is trademark of Huace Navigation Limited.
Manual
Edition I May 2002
Edition II Nov. 2002
Edition III July 2003
Edition IV Jan. 2004
Edition V June 2004
3. Important Announcement
We will have periodical modification of the contents of this manual. Modified editions
go with new purchased software. You can read it with the reader goes with software
and print it out. You are welcome to call us for the information of new manuals. Latest
manuals are also available online.
177

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