About
Online GRF-TT transformation tool
Online
GRF-TT is the tool for
transformation of geodetic coordinates between KSA GRFs (Geodetic
Reference Frames).
The coordinates could be either geographical or UTM projection
coordinates.
Standard Helmert
parameters (translation, rotation and scale factor) are used for coordinate transformation from geodetic reference frames ARAMCO (ITRF 1994, epoch 1998.0),
GDMS (ITRF2000, epoch 2003.1998), MTRF-2000 (ITRF2000, epoch 2004.0), and WGS84 (defined in EPSG-9383 as ITRF2014 at the epoch 2010.0) to KSA-GRF17 (solution of March
2019). A grid of 3D transformation parameters is used for transformation
from ARAMCO Ain Al Abd (1970) reference frame to KSA-GRF17. KSA-GRF17
ellipsoidal heights can be transformed to orthometric heights (referenced to the geoid
surface) by using a 1D transformation grid
derived from the Hybrid Geoid KSA-GEOID21 model (Technical Summary for Saudi Arabia National reference System (SANSRS)). This model the latest in the Kingdom of Saudi Arabia national hybrid geoid model, and it is fitted to geoid heights of 3522 GASGI GPS/levelling benchmarks from National Vertical Network..
Online GRF-TT can be used in two modes:
-
Single Point (one
point) mode, when before the transformation, the user has to input the values
of the following coordinates into the proper
data input fields in the GUI, depending on the Source
Coordinate Type:
·
Geographical coordinates: (Geodetic Latitude,
Longitude) or (Geodetic
Latitude, Longitude, Ellipsoidal Height)
·
UTM
projection coordinates: (Northing, Easting) or (Northing, Easting,
Ellipsoidal Height)
-
MultiPoint mode (multiple
points (each point must have its
own name for identification) saved into Input (Upload) File) which
is using the same Source Coordinate Types as for the Single Point
mode except of DMS measurement units.
Online GRF-TT is able to
transform data having the values only within the following range values covering the KSA
area:
·
latitude:
16.02° – 33.00°
·
longitude:
34.00° – 56.00°
·
ellipsoidal height: -40 meters to 3200 meters
·
Northing: 1660514 – 3655285 [m]
·
Easting: 177349 – 822651 [m].
If the
input coordinates are out of these ranges the coordinates of such point will
not be transformed and the user will see, in the Single Point mode, corresponding error
indicators above the data
entry fields and “Out of
range” error message in the result output window. In the MultiPoint mode, this error
message will appear for all such points in
the result output file.
More
details about use of Online GRF-TT can be found in Online GRF-TT User
Manual.pdf
Single Point mode - input the values in the proper fields according
the formats of the selected Source Coordinate Type:
·
Geographical
coordinates: either in decimal degrees [°] (up to 8 digits
after the decimal dot) or in DMS -
angular degrees [°], minutes
[ʹ],
seconds [ʺ] (up to 5 digits after the decimal dot) for
the latitude Lat and longitude Lon, and in meters [m] for ellipsoidal height Height (up to 3 digits after the decimal point) by paying attention to the value ranges specified under each
input field.
·
UTM
projection coordinates: in meters [m] (up to 3 digits after the decimal dot) for
all coordinate components by paying attention to the value ranges specified under each
input field.
MultiPoint mode – each point’s data takes one separate record
line both in the Input (Upload) File and Output (Results)
File (ASCII *.txt files), and contains the point id
(created of letters, numbers and symbols with no spaces between them), followed
by the two or three coordinate values expressed depending on the Source
Coordinate Type as either
·
geographical coordinates: in decimal
degrees [°] for the latitude Lat and longitude Lon, and in meters
[m] for ellipsoidal height Height, or
·
UTM projection coordinates: in meters [m]
for all coordinate components
and separated with at least
one space in between the values. The range value requirements described for the
Single Point mode input data must be applied to the Input File
data too.
Input File to
upload has 3 or 4 values in each record line depending on the Source
Coordinate Type. The range value requirements described for the Single
Point mode input data must be applied to the Input File data
too. The Input File must have one empty line at the very
end of the file.
Examples (the
first line is given in the examples just to describe the order and
meaning of the values):
id
Lat [°] Lon [°]
AB01 23.43546534
46.42938473
id
Lat [°] Lon [°] Height [m]
AB01 23.43546534 46.42938473
351.655
id
Northing [m] Easting [m]
AB01 2211793.556
604609.324
Id
Northing [m] Easting [m] Height [m]
AB01 2211793.556
604609.324 351.655
Output File to
download will be generated by Online GRF-TT. It has 7 or 8
values in each record line depending on the Target Coordinate Type. Each
line contains point id, two or three output coordinate values, Convergence,
Full Scale Factor, Geodetic and Vertical Position Precision
values.
At the top of the file, there is information about Input
File name, Source and Target Coordinate Reference Systems,
and measurement units.
Examples:
id Lat [°] Lon [°] Convergence [°] FullScale GeodeticPreicison VerticalPrecision
AB01 23.43546534
46.42938473 -0.606006 1.0001945 < 5
cm no info
id Lat [°] Lon [°] Height [m] Convergence [°] FullScale
GeodeticPreicison VerticalPrecision
AB01 23.43546534
46.42938473 347.483 -0.606006 1.0001945
< 5 cm no
info
id Northing [m] Easting [m] Convergence [°] FullScale
GeodeticPreicison VerticalPrecision
AB01 2211793.556
604609.324 -0.606006 1.0001945 < 5
cm no info
id
Northing [m] Easting [m] Height [m] Convergence [°] FullScale GeodeticPreicison
VerticalPrecision
AB01 23.43546534
46.42938473 347.483 -0.606006
1.0001945 < 5 cm no info