4.1.2. Measurements
In the submenu Input > Measurements the GPS or Total Station measurements
are shown and stored. The functionality of the Measurements dialog depends on
the current selected station (GPS or Total Station). The menu can also be opened with the button shown above.
Total Station:
In this window the
total station measurements have already been corrected in terms of the
instrument constants entered under Initial
> Instrument.
In the field PtNo. enter the
designation of the point to be measured. In the field Cod
you can allocate the point code and the marker type is specified in the
field MA. CP characterizes the
point when it is activated as a control point. H specifies the horizontal angle, V the vertical angle, and D the
distance.
The measurement is triggered via the appropriate buttons. The button <Meas>
initiates the angle and distance measurement. By means of the button <Raw>
a coarse measurement is initiated with a shorter measurement period yet with
reduced accuracy. The buttons <Angle>
and <Dist> only deliver the
angle or the distance and vertical angle respectively. <Build> is conceived for
measurements using reflectors in the case of buildings. After the
measurement has been successfully carried out, the dialog switches into the save
mode.
After the measurement elements have been registered, the target height t,
the longitudinal ex-center L (set to
0.2 m in the case of building measurements), the transverse ex-center Q
and the distance eccentricity S are
entered in meters. You can save the measured values with <OK>,
or reject them with <X> and
return to the previous dialog.
Servo-driven instruments can be controlled by the button <Servo>.
GPS:
For
the display of the GPS coordinates GART-2000®
CE uses the coordinate
system chosen in the Initial
> Constants > GPS submenu.
The following data are displayed:
| E |
East-coordinate
in the user system with the standard deviation [m]
|
| N |
North-coordinate
in the user system with the standard deviation [m]
|
| H |
Height
of the coordinate in the user system with the standard deviation [m]
|
| Sat |
Number
of satellites used for the position calculation (GPS|GLONASS)
|
| PDOP |
PDOP:
factor to determine the reachable accuracy dependent on the satellite
geometry.
|
| I.H. |
Antenna
height (true vertical height of phase center above the ground point)
|
| Radio |
Display
of the radio link quality
|
| D |
Distance
to the reference station in [m]
|
| Solution |
Display
of the ambiguity fixing status and the chosen dynamics of the GPS-Rover
receiver. |
The status of ambiguity fixing may be the
following:
- fixed:
PDGPS-solution with fixed ambiguities.
- float:
PDGPS-solution with code and carrier-phase corrections.
- Code diff:
DGPS-solution with code corrections.
- autonomous:
autonomous position of the receiver.
- invalid:
position calculation impossible.
The calculation of the ambiguities in the GPS receiver is influenced by the
chosen dynamics. The dynamics describe the movement of the GPS antenna.
With
the button >> the dynamics can
be chosen from a list.
Possible settings for
TPS are "static" and "walking".
For Ashtech-receivers there are "quasistatic",
"walkingr", "automobile"
,”aircraft” and "ship"
additions.
The button <Sat> displays
detailed information about the tracked GPS/GLONASS satellites.
The satellite overview displays the satellite number, the azimuth, the elevation
and the signal/noise-ratio of the different satellites on the screen. For
TPS-receivers the GPS satellites are marked with a 'G‘, GLONASS satellites
with a 'N' in the first row. For Ashtech receivers you will see a flag ('-' or
'U' ). The satellites are marked with a 'U' if differential corrections exist
for a satellite. Otherwise, a '-' is shown.
The button <Sky-Plot> shows the
actual satellite geometry.
By pressing the <Info> button,
a button strip is shown; if pressing these buttons further information from the
GPS receiver are queried.
The following functions are supported:
| <Dref> |
This
function reads the coordinates of the Base receiver from the RTCM messages
and saves it. These coordinates are used to calculate the distance from
the Rover to the Base receiver (D). |
| <Radio> |
The
status of the received correction data is displayed.
Ashtech-receivers:
RTCM-Age:
Age of the differential
corrections in seconds.
RTCM-Quality:
Display of the radio-quality in percent.
Data:
Flag to show the data:
'+‘ Data are okay
'-' No reception.
In addition, the satellites for which differential corrections are
received are shown in the screen.
TPS-receivers:
Radio Link: Display of the radio
quality in percent.
RTCM-Age:
Age of the differential corrections in seconds.
RTCM-OK:
Number of correct received sets of differential corrections.
RTCM-corrupt:
Number of incorrect received sets of differential corrections. |
| <Stat> |
Statistics
about the position calculation. |
| <Extra> |
Possibility
to change the elevation mask and the environment type (forest or open
sky). (Only for TPS
receivers) |
| <VRS> |
Settings
can be made here pertaining to the use of a virtual reference station.
Ionospheric model:
Activate
this module if the ionosphere is disturbed. The standard value for Sigma
is 5. When VRS services are implemented, the date and time are shown
in the field Time, the network
status in the field Status, and
receiver information in the field Mode.
Zero antenna:
Activate this module when a zero-centered antenna is used. The set of
parameters required for the calculation is currently only available for
the TPS (Topcon Positioning System) LegAnt
antenna.
These
settings are only available for TPS
receivers at the moment. |
| <Vector> |
The
absolute coordinates of the Base are displayed in Cartesian coordinates as
well as the Base-Rover vector.
By checking the checkbox Vector data recording, the correlations of the coordinates are also
saved. The displayed distance D
to the reference station is updated automatically.
The
vector data recording can be started with the aid of the Vector dialog. To
this end, the corresponding checkbox should be checked. The Cartesian
coordinate of the reference station is displayed in the Base
fields, the vector between Base and Rover in the Rover fields. |
| <Power> |
Indication
of the battery capacity. This function works only for the Ashtech
Z-Surveyor with internal battery. The voltage and the capacity as well as
the maximum and remaining battery time are shown. |
| <Contrast> |
Indication
of the Contrast Ratio Value.
The
contrast value declares how reliable the fixing of the ambiguities is.
Ashtech: Range from 0.00 up to 999.0. A value higher than 1.0 indicates
that the ambiguities are fixed. |
The
button >>
next to the field <Ant.Height> in the GPS-Measurements
dialog opens the submenu for the Antenna height. Choose the manufactory and the
antenna type. For each antenna type the individual antenna offsets are shown.
Enter the type of antenna height measurement:
-
instrument
height: measured from the marker to the bottom of the antenna at the
base of the mounting threads,
- slope: measured from
the marker to the lower edge of the groove around the antenna at the seam
between the top and bottom halves of the antenna casing.
In the field Measured enter your slope or vertical antenna height. The true
vertical height will be calculated immediately and will be shown in the field Calc (TV).
After exiting this window with the <OK>
button, the true vertical height will be set as antenna height in the
measurement window.
The true vertical antenna
height in GART-2000®
CE allows for different
antenna offsets in case different antenna types are used on base and rover. In
addition to the predefined antenna types in the list, you may enter your own
antenna types. To do so enter a new name for your antenna and edit the values in
the offset fields. The button <Save> stores the new entry.
With
the <Reset>-key a reset of the
RTK engine is done. The fixing of the ambiguities is restarted. If the
ambiguities are fixed you see the status "fixed".
By
pressing the <Save>- or the <OK>-button
the current coordinates can be stored; therefore it is possible to average
several measurements. The number of measurements to be averaged is defined in
the Initial
> Constants > GPS menu. The displayed standard deviations in the
averaging window result from the averaging process of the measurements. To
receive realistic values for the standard deviations the values will not
decrease below the actual standard deviations from the GPS receiver.
The
point number can be entered after the averaging process. GART-2000®
CE suggests a new point
number according to the interval entered in the submenu Initial
> Constants > Point Numbers. Moreover the point type, the marker
type and an optional comment are stored with the coordinate. In addition to
that, for cadastral applications the precision of position (LG)
and the reliability of position (LZ)
as well as the precision of height (HG) and the reliability of height (HZ) can be changed.
The
<X>-button closes the
measurement menu.
<TABLE
OF CONTENTS>