Post on 12-Jan-2016
description
Permanent GPS Stations in Israel as Basis for
Updated Geodetic Network
Gilad Even-TzurFaculty of Civil and Environmental Engineering
Mapping and Geo-Information Engineering
Technion, Haifa 32000, Israel
Moshe Rozenblum, Einat SalomonSurvey of Israel
1 Lincoln St. Tel-Aviv 65220, Israel
Permanent GPS Stations in Israel, Sept. 2005
17 StationsReceivers: 11 Ashtech Z-XII
5 Leica SR5301 Trimble 5700
Antennas: 9 Ashtech DM5 Leica DM2 Topcon CR41 Trimble DM
Permanent GPS stations in Israel, Sept. 2005
10 stations are situated on stable roof tops
NRIF
Permanent GPS Stations in Israel, Sept. 2005
7 stations have geodynamic monuments
LHAV
The Control CenterThe GPS receivers are connected to a control center, equipped with master and backup servers, through frame relay connections.
The Communication Network
The GPS Data Flow
5 sec sampling rate Data is downloaded in real
time The RINEX data is
gathered into 1-hour interval files and posted on the internet
Operation Manager Software
The network is controlled by the RTD software.
It is based on epoch-by-epoch technology, which enables monitoring any changes in the station coordinates due to deformation and lost qualities.
Permanent GPS Stations in Israel, Sept. 2005
RAMO is the official IGS station in Israel
The data is processed at SOPAC
The data from RAMO and DRAG is also processed at GIBS (GPS-Informations- und
Beobachtungssystem )
The Permanent GPS Stations in Israel are called:
APN
Active Permanent Network
Free 30 sec sampling rate data is available at:
ftp://212.179.112.235
Until recently, the APN network was mainly used for geodetic and geophysical research.
The APN was used less for surveying purposes:
- Short sessions- OTF ambiguity resolution
used - Lack of transformation
between WGS84 and ITM
The APN Network
VRS - Virtual Reference Station
In order to enable GPS surveying over the entire state of Israel with direct connection to the permanent GPS network, VRS technology is applied.
Economically and practically, there is no need to increase the number of permanent GPS stations in Israel.
The VRS is produced by the GEO++ software
User Interface for Receiving Data
Advantages of Using the APN
Uniformity Accuracy
Reliability Simplicity
► In the near future an RTK option will be added to the APN network
► Geodetic datum is a set of parameters and control points used to: ● Define the size and shape of the earth.● Define the origin and orientation of the coordinate systems used to map the earth.
► The datum is the basis for a plane-coordinate system.
► Geodetic datums range from flat-earth models used for plane surveying to complex models used for international applications.
Datum Definition
► GPS positions and vectors are referenced in the WGS-84 datum
► The Israeli coordinate system is referenced in the GRS-80 reference ellipsoid with geodetic projection called:
ITM - Israel Transverse Mercator
Datum Definition (continuance)
x
y
z
dX
dY
dZ
m
R
R
R
Shifts
Scale
Rotations
Transformation parameters describe the relations between two different datum systems.
7 Parameter transformation:
Datum Transformation
'84 '84 '84 80 '84
'84 '84 '84 80 '84
'84 '84 '84 80 '84
1 0 0 0
0 1 0 0
0 0 1 0
X WGS WGS WGS GRS WGS
Y WGS WGS WGS GRS WGS
Z WGS WGS WGS GRS WGSX
Y
Z
dX
dY
V X Z Y X XdZ
V Y Z X Y Ym
V Z Y X Z ZR
R
R
The set of transformation parameters is determined by a least-squares solution:
Datum Transformation (continuance)
► Each point from the APN network was connected by GPS observations to the nearest 1st order control points. ► A local datum transformation was calculated in order to assign plane coordinates to each permanent GPS station.
The Plane Coordinates of the APN Points
The accuracy of the coordinates is equivalent to the accuracy of the classical 1st order
control network (~10cm)
Permanent GPS Network
A permanent GPS-based network is obviously more accurate, reliable and homogenous than a
classical network.
Permanent GPS Network
Supreme Network
A set of coordinates that was valid for GPS day 275 of the year 2004 (October 1st , 2004) in the ITRF2000 coordinate system was set as the fixed coordinates set for the permanent GPS stations
New Datum for APN
This set of coordinates defined a new datum for APN, called
IGD05
Israel Geodetic Datum 2005
Horizontal residuals resulting from the seven parameters transformation between the ITRF2000 (IGD05) datum and the
Israel Grid datum
5cm
50km
ScaleNetwork:
Residual:
A new set of plane coordinates were adopted for the APN points.
New Datum for Israel Grid
The new coordinates defined actually new datum for the Israeli Grid called:
IG05
Israel Grid 2005
The adopted plane coordinates is a result of similarity transformation between two datums (IGD05 and
IG05) which supplied practically zero residuals in the least-squares process.
Official 7 Parameters Transformation
IGD05
IG05
Calculate official 7 parameter transformation between the two systems
A flow chart for calculating new control points in IG05 coordinate system
Measuring methods for establishnew control point
1. Relative to APN station
2. Relative to VRS
3. Relative to base station
4. Geodetic network
Field Work Guidelines
► Two independent Observation sessions
► Observation sessions of at least 10 min
► Time duration between two sessions of at least 60 min
1. Measuring relative to APN station
10km
TELA
First session:
10min 10min
10min
10min
TELA
10min
10min
10min
Time duration between sessions – 60 min
1. Measuring relative to APN station
Second session:
5km
VRS1
10min 10min
10min
10min
2. Measuring relative to VRS
First session:
VRS2
VRS1
VRS3
The distance between two VRS should be at least 120m
10min
10min
10min
Time duration between sessions – 60 min
2. Measuring relative to VRS
Second session:
VRS2
VRS1
VRS3
Measured vectors:
2. Measuring relative to VRS
► Connect the base station to IGD05 system 10km
BASE
90min
IGD05
IGD05
3. Measuring relative to base station
BASE
10min 10min
10min
10min
IGD05
IGD05
► Measuring new control points
First Session:
3. Measuring relative to base station
BASE
10min
10min
10min
ILGD05
ILGD05
3. Measuring relative to base station
► Measuring new control points
Second Session:
Time duration between sessions – 60 min
Assume work with 3 receivers
1
IGD05
IGD05
2
3
4
- Sessions of at least 10 min- Each new point should be measured in two independent sessions
4. Measuring Geodetic Network
The Geodetic-Geodynamic Network (G1)
► Includes 160 points that homogeneously cover the state of Israel
► The location of the points was determined mainly according to geological considerations
►The points were built according to very high technical specifications, to ensure their geotechnical stability
The goal of the Geodetic-Geodynamic Network
► A potential geodetic network for monitoring deformations in primary and secondary known faults
► Serves as the major geodetic control network of Israel
The Measurement Campaigns► During 1996 the G1 network was measured for the first time (Blue circles and Red squares)
► The second campaign was held in 2002
► Only 100 points were measured (Blue circles)
► 5 new points were fixed in the northern part of the network (Yellow circles )
► 11 continuous permanent GPS stations were operated (Green triangles)
► the accuracy of the points is better than 1cm
The G2 Network
► Abut 1000 points that organized in closed loops
► Most of the points are BMs from the Israeli vertical control network
► The points were measured during long period and not as one campaign
► The network accuracy is not homogeneous and not satisfactory (~5cm)
Vertical Control
► Survey of Israel (SOI) decided that the future vertical control in Israel will be based on ellipsoidal heights instead of orthometric heights
► SOI will support and maintain spatial geodetic network which will serve as horizontal and vertical control
► The APN and G1 will be used as basis for ellipsoidal vertical control
► Undulation model will be used to convert ellipsoidal heights to orthometric heights