Permanent GPS Stations

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Permanent GPS Stations and their Influence on the
Geodetic Surveys in Israel   Gershon
Steinberg Survey of Israel 1 Lincoln St. Tel-Aviv
65220, Israel Gilad Even-Tzur Mapping and
Geo-Information Engineering Technion, Haifa
32000, Israel (consultant to SOI)
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Permanent GPS Stations in Israel, October 2006
? 18 Stations Receivers 7 Ashtech
Z-XII 6 Leica SR500 5 Leica
1200 PRO Antennas 9 Ashtech DM 6
Leica DM 2 Topcon CR4 1 Trimble
DM
Upgrade to GLONASS is coming up soon
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Permanent GPS Stations in Israel, October 2006
? 11 stations are situated on stable roof
tops
NRIF
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Permanent GPS Stations in Israel, October 2006
? 7 stations have geodynamic monumentation
LHAV
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The Control Center
The GPS receivers are connected to a control
center, equipped with master and backup servers,
through IPVPN connections.
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The Communication Network
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The GPS Data Flow
? 1 sec sampling rate ? Data is downloaded in
real time ? The RINEX data is gathered
into 1-hour interval files and posted on
the internet
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Operation Manager Software
The network is controlled by the RTD software.
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Permanent GPS Stations in Israel, October 2006
? RAMO is the official IGS station in
Israel ? All the data is processed at SOPAC
(Scripps Orbit and Permanent Array Center)
? The data from RAMO and DRAG is also
processed at EPN (EUREF Permanent Network)
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The Permanent GPS Stations in Israel are called
APN Active Permanent Network
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The VRS and RTK Options
In order to enable GPS surveying over the entire
state of Israel with direct connection to the
permanent GPS network, VRS and RTK technologies
are applied.
The VRS and RTK are produced by the GEO software
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The Plane Coordinates of the APN Points
? Each point from the APN network was connected
by GPS observations to the nearest 1st order
control points. ? A local datum transformation
(3D) was calculated in order to assign plane
coordinates to each permanent GPS station.
The accuracy of the coordinates is equivalent to
the accuracy of the classical 1st order control
network (6cm)
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Permanent GPS Network
A permanent GPS-based network is obviously more
accurate, reliable and homogenous than the
classical network.
Permanent GPS Network
Supreme Network
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New Datum for APN
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
This set of coordinates defined a new datum for
APN, called IGD05 Israel Geodetic Datum 2005
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Horizontal residuals resulting from the seven
parameters transformation between the ITRF2000
(IGD05) datum and the Israeli Grid
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New Datum for Israel Grid
A new set of plane coordinates were adopted for
the APN points by adding the residuals of the
transformation.
The new coordinates defined new datum for the
Israeli Grid called IG05 Israel Grid 2005
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Official 7 Parameters Transformation
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A flow chart for calculating new control points
in IG05 coordinate system
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Geodetic Control Networks

• The National Geodetic Control Network will be
  defined as 3D control.
• The network is based on the Permanent GPS
  stations of Israel (constitute the higher order).
  
• - Primary 3D class G
• - Secondary classes
• S
  horizontal coordinates.
• E ellipsoidal
  heights.

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  Horizontal Control

• The primary objective of the horizontal control
  network is to serve the cadastral surveys.
• The goal is to define the cadastral boundaries
  with an accuracy of 5cm (95).

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National Control Network Classification and
Required Accuracy
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  Vertical Control

• Ellipsoidal Control
• There is neither practical possibility nor actual
  need to maintain a country-wide vertical
  orthometric control network.
• SOI will maintain vertical ellipsoidal height
  control network.

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National Control Network Classification and
Required Accuracy
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Orthometric control

• The transition to ellipsoidal heights only, is
  premature yet.
• The orthometric heights will be used as having a
  local datum.
• HL can be measured either by geometric leveling,
  trigonometric leveling or GPS based on local
  benchmarks.
• HS (statutory heights) measured by GNSS and
  official geoid undulations model (OGUM).

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THE IDEA OF OFFICIAL GEOID UNDULATIONS MODEL
(OGUM) AS A SUBSTITUTE FOR ORTHOMETRIC CONTROL

• A very important objective of the leveling
  network is to bring consistent identical heights
  by every surveyor.
• There is no need to wait for the "perfect" geoid
  model.
• We suggest declaring the best available Geoid
  Undulations Model as an Official Model (OGUM).
• The combination of OGUM with vertical Ellipsoidal
  Control based on CORS, produces a practical
  country-wide network of Orthometric Height
  Control, appropriate for most of the
  geodetic/surveying needs.

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Vertical Local Orthometric Control Networks
Levels and Required Accuracy

• New D is the horizontal distance.
• HL1 and HL2 can be measured by leveling only.
• HL3, HL4, HL5 can be measured by GPS also.
• E1 will produce HS1 and E2 will produce HS2.

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Experiments In Israel

• Goal To examine the accuracy of orthometric
  height differences based on GPS measurements and
  OGUM in different locations in Israel.
• Two alternatives for OGUM
• 1. ILUM1.0 - Israeli Undulations Model, Based on
  750 Benchmarks.
• 2. GPM98B- Global Geopotential Model (Wenzel),
  contains few gravity data from Israel.

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Experiments In Israel (cont.)

• Six height-differences (between 4 adjacent
  benchmarks) were measured simultaneously by GPS
  (40 minutes' sessions).
• The relative accuracy of the known orthometric
  height -differences, as well as the measured
  ellipsoidal height- differences, is 1-2cm.

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Experiments In Israel (cont.)

• Eight locations where the OGUM experiment was
  held in Israel.
• The numbers denote the place's name as appears in
  the next table.

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Experiments - Results

• The RMS and the mean PPM values of the
  differences between the known orthometric
  height-differences and the orthometric
  height-differences obtained by GPS and the two
  alternatives for the OGUM.

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Discussion

• For a reasonable orthometric control we
  actually need a height-differences accuracy of
  25mm for benchmarks 1km apart (25PPM).
• We achieved this goal in all our experiments with
  the temporary Israeli OGUM. It was achieved also
  using the Global model, except for Eilat.
• The results demonstrate the capability of the
  idea, for most of the engineering works.
• Not instead of existing good networks.
• A special benefit for areas were establishing a
  leveling network is practically impossible.