1. Setup “Do’s & Don’ts Presented By:
SCS900
Setup
“Do’s & Don’ts
Presented By:

2. Finding a suitable location to set up the GPS base station
T – Bar Setup (Permanent)
Fixed Height Tripod Setup
(Mobile )

3. The Do’s Location that is preferably central to the project
Base Station as high as possible
Base Station receiver does not lose power
Location that can easily be reproduced
Protected and Secure location
Set up the GPS base station in a location that is preferably central to the project
site, so that it can deliver RTK corrections over the radio for the maximum range
in all directions.
• Set up the GPS base station as high as possible, so that the GPS antenna is clear
from obstructions, and so that the radio antenna delivers the best possible
transmission for the maximum possible range.
• Make sure that the base station receiver does not lose power. It can be powered
by its internal batteries or, by an external 12 V power supply or AC power. For
permanent installations, AC power (also known as mains power) is preferable.
The internal battery will always charge from AC power and thereby provides an
uninterruptible power supply in times of AC power failure.
• Establish the base station at a location that can easily be reproduced if the
receiver is likely to be taken down at the end of operations each day. The most
effective means of creating a reproducible location is to build a T-Bar (see
here).
Place the GPS receivers in a protected and secure location. If the base station is
in the center of a jobsite where heavy machinery is operating, place flags around
the base station to warn operators of its existence
Trimble recommends that you install lightning protection equipment at
permanent base station locations. A static dissipater near the antennas can reduce the likelihood
of a direct lightning strike. Also protect any communications and power lines at
building entry points.
Trimble recommends that you use surge protection equipment on all
permanently installed equipment.

4. The Don’ts Radio transmission equipment Trees Tall Buildings Ponds
Overhead power lines
Electrical generation facilities
Do not locate a GPS receiver, GPS antenna, or radio antenna within 400 meters
(about 1,300 feet) of:
– a powerful radar, television, or cellular communications tower
– another transmitter
– another GPS antenna
Cell phone towers can interfere with the base station radio broadcast and can
stop corrections from reaching the rover receiver. High-power signals from a
nearby radio or radar transmitter can overwhelm the receiver circuits. This does
not harm the receiver, but can prevent the receiver electronics from functioning
correctly.
Low-power transmitters, such as those in cell phones and two-way radios, do
not interfere with receiver operations.
Do not place the GPS antenna near vertical obstructions such as
buildings, deep cuttings, site vehicles, towers, or tree canopy
Do not set up the base station directly beneath or close to overhead power lines
or electrical generation facilities. The electromagnetic fields associated with
these utilities can interfere with GPS receiver operation. Other sources of
electromagnetic interference include:
– Gasoline engines (spark plugs)
– Televisions and computer monitors
– Alternators and generators
– Electric motors
– Equipment with DC-to-AC converters
– Fluorescent lights
– Switching power supplies

5. Good or Bad

6. SCS900
Starting SCS900

7. Operation Modes Basic Features Basic+ Features Full Features
designed to meet the needs of those site users who require minimal functionality
Basic+ Features
enables the site supervisor to establish the base station, enter control point coordinates and then carry out a site calibration in addition to using all the features in the Basic Features operation mode
Full Features
all the features available
Basic Features operation mode – This mode provides a very simple version of
the SCS900 software, which is designed to meet the needs of those site users
who require minimal functionality. A skilled operator can set up a site and then
leave a basic system for a less-skilled operator to use. Typically, a site supervisor
or foreman can use the Basic Features operation mode every day on the same
site, enabling them to review digital design information and view real-time cut
and fill data. The log file capability enables them to start to record information
for simple as-built grade checks on the site, once grading operations are
complete.
• Basic+ Features operation mode – This mode enables the site supervisor to
establish the base station, enter control point coordinates and then carry out a
site calibration in addition to using all the features in the Basic Features
operation mode.
• Full Features operation mode – This mode contains all the features available in
the SCS900 software.
The software is installed with all features. While selecting an operator name, the user
can select a login type that controls which functions are available to them. There is no
security associated with this login process; it is simply a mechanism to control which
features the operator can access.

8. SCS900
Main Menu Structure

9. Main Menu Structure SCS900 software Is Two main functions
menu-driven system
ease of use and learning
access to six submenus
Two main functions
Measurements
Stakeout
1. Measurements – This function enables you
to measure and record the location, or
as-built location, of features or surfaces or
objects on a project, or to collect
information that allows you to create a
surface model, from which you can make
volume computations, and grade or material
thickness checks.
2. Stakeout – This function enables you to
stake or relocate any aspect of the site
including point features (such as manholes),
line features (such as curbs, foundations, and
footings), planar surface features (such as
pads), or surfaces (such as site terrain
models, side slopes and catch points, or road
surface models).

10. Work Orders menu Work Orders menu New Open Change Design
Complete Work Order
Export/Import Data
The Work Orders menu contains the tools to create, open, and complete work orders.
The menu also provides the capability to change the design referenced by the current
work order, and output new design data from the current work order, for example, the
original ground topographic measurements.
New –
Create a new work order in the field as required for a
requested task, for which no work order has been provided.
The SCS900 software creates a new work order that references
a specific site and design.
Open-
Open an existing work order. This can be:
• a new work order, created by the supervisor, which you are
to carry out
• an in-progress work order, which you need to retrieve data
from or add data to
• a previously completed work order, which you need to
reopen to retrieve information or to add information to
Change Design-
Select a different design, which provides different information
to that currently loaded, as a result of a change in the design
for the project, or a request to do something within the
current work order that requires different design data.
Complete Work Order-
Complete the currently open work order and write the
Work-Order Measure.dxf file.
Export/Import Data-
Write the surface data that was measured in the field to a new
design surface; export the site calibration file to a
CompactFlash card; export a design to a CompactFlash card for
use with the GCS900 Grade Control System, save site
calibration data to a memory card; and send or receive files
from “intelligent” s.

11. Measurement menu Measurement menu Check Surface Grade
Check Grade of Roadway
Check Material Thickness
Measure Surface
Measure Site Features
Display Real-Time Cut/Fill
Advanced Measurements
The Measurement menu contains all site measurement functions. With the dedicated
functions, you can check grades and material thickness, take topographic
measurements to create surface models ( for example, volume computations), take site
feature measurements to record the location of non-surface features, and provide
real-time cut/fill information against a selected design model.
Before you enter this menu, set up the system using the System Setup menu. If you do
not, when you select an option in this menu, the software automatically puts you
through either the station establishment process ( for a total station) or the rover setup
( for GPS).
Check Surface Grade-
Check the grade of a surface against a selected design. This
option is available only when the current design is not a road.
Check Grade of Roadway –
Specify a high or low tolerance for the finished grade and
check whether or not the grading operations have achieved
tolerance.
This option is available only when the current design is a road.
Check Material Thickness-
Check the thickness of laid materials against the specified
thickness.
Measure Surface-
Measure a surface: points, break-lines, volume boundaries, and
the site boundary.
Measure Site Features-
Measure site features not used in the creation of a surface.
Display Real-Time Cut/Fill-
Check current cut and fill at any location on the project against
the original ground, finished design, or any other surface.
Advanced Measurements-
Scanning options for use with total stations, specifically for
scanning stockpiles or recording profile lines of objects like
quarry walls or high walls. Automated point measurement
enables prisms or targets to be repeatedly measured to check
for movement, and s can notify users of movement
outside of the set tolerance.

12. Stakeout menu Stakeout menu Point Line Side Slope & Catch Point Plane
Surface / Road
Enter/Edit Stakeout Points
The Stakeout menu contains all SCS900 stakeout functions including staking points,
lines and alignments, planes, surfaces, side slopes, catch points, and road features.
Before you enter this menu, set up the system using the System Setup menu. If you do
not, when you select an option in this menu, the software automatically puts you
through either the station establishment process ( for a total station) or the rover setup
( for GPS).
Point-
Stake individual point data. The software guides you directly to
the point.
Line-
Stake lines and alignments or offsets to lines using station and
offset methods. The software guides you directly to the line.
Side Slope & Catch Point-
Stake an earthwork operation that involves a tie to the current
ground surface.
Plane-
Create and stake out a level plane, a sloping plane, or a 3-point
plane. The software guides you directly to points on the plane.
Surface-
Stake out from a design surface. The software guides you
directly to points on the surface.
This option is available only when the SCS900 road module is
not installed.
Road Stake-
roadway features, sideslopes, and catch points or any
point on the surface.
installed.
Enter/Edit Stakeout Points-
Add, edit, or delete any stakeout points that are in the current
design.

13. Settings menu Settings menu Units & Formats GPS Settings
Internet & VRS Settings
Instrument Setup & Adjustment
Stakeout Settings
Data Output Options
COM Port Data Output Option
Radio Baud Rate
The Settings menu contains all the SCS900 system settings that control the units of
measurement, how the software operates, and what tolerances the software will use for
different functions during operation.
The settings provide control over Internet connectivity for VRS or remote base station
GPS operations.
The settings also control what data is recorded during operation and then exported
when a work order is complete.
Units & Formats-
Specify the measurement units and the order of coordinates.
GPS Settings –
Specify GPS measurement and site calibration tolerances.
Internet & VRS Settings-
Configure your Internet connection for use with “intelligent”
functions, a VRS system, or create a new connection with
the New Connection wizard.
Instrument Setup & Adjustment-
Specify horizontal, vertical, and angle setup tolerances and the
type of corrections to apply to the measured distance
Stakeout Settings-
Specify stakeout methods to be used, stake writing
information, stakeout tolerances, and auto-aim controls for use
with a total station. Select map view options.
Data Output Options –
Specify .dxf file output options (surface measurements and/or
3D faces). Specify whether or not raw data will be output with
each record
COM Port Data Output Option-
Enable the controller to output the instrument measurement
data through a COM port.
Radio Baud Rate-
Change the receiver to radio baud rate for third-party and
Trimble PDL 450 radios.

14. Volume & COGO menu Volume & COGO menu Review & Edit Surface
Review Design Features
Compute Distance & Area
Create Stakeout Points
Create/Edit Road Data
The Volume & COGO menu contains a number of calculation (area, distance, bearing,
slope) and point generation functions ( free point, offset points, radius point) that can
be used to generate points for stakeout operation from CAD data in the currently
loaded design.
The menu provides access to the contour generation function, which you can use to
review a measured surface before you use the Compute Volume option, to determine
stockpile or progress volumes. The menu also provides access to review and edit
functions for editing breaklines and deleting points or lines to resolve surface
modelling problems
Review & Edit Surface-
View or delete point and lines, add breaklines and boundaries,
contour surface and calculate surface volumes (stockpiles) or
periodic progress volumes.
Review Design Features-
Calculate volumes based on the design data, and calculate
distances and areas.
Compute Distance & Area-
Compute areas, distances, and angles from measured or
stakeout data.
Create Stakeout Points-
Create points by a variety of methods including free point,
radius, and offset to a line. Free points can be created by
tapping the screen or entering coordinates.
Create/Edit Road Data-
Enter a roadway and perform COGO functions based on a road.
This option is available only when the SCS900 road module is
installed.

15. System Setup menu System Setup menu (GPS) Set up Base Set up Rover
Calibrate Site
Recheck System Setup
Enter/Measure Control Points
Switch to Total Station Setup
The System Setup menu contains the control and system setup functions for GPS
For GPS, use the menu to start the base station, start the rover receiver, and then
carry out the site calibration process.
General functions include being able to enter and edit control point information,
measure new control points for the project, and recheck the system setup on a control
point.
The menu also provides the ability to switch between GPS and total station operations.
Set up Base-
Set up and start a Precision GPS base station.
Set up Rover-
Set up and start a GPS rover.
Calibrate Site-
Perform or resume a single-point, two-point, or multi-point
site calibration.
Recheck System Setup-
Check an existing site calibration on a known control point.
Enter/Measure Control Points-
Edit and enter control point coordinates.
Switch to Total Station Setup-
Access the Total Station System Setup menu.

16. System Setup menu System Setup menu (TS) Connect Instrument
Set up Total Station
Instrument Functions Menu
Recheck System Setup
Enter/Measure Control Points
Switch to GPS System Setup
The System Setup menu contains the control and system setup functions for GPS or
total station operation:
• For total stations, use the menu to connect the instrument and carry out station
establishment to establish the position and orientation of the instrument. The
menu provides access to all total station control functions and calibration
procedures.
General functions include being able to enter and edit control point information,
measure new control points for the project, and recheck the system setup on a control
point.
The menu also provides the ability to switch between GPS and total station operations
Connect Instrument-
Connect to the total station using a radio for robotic
operation or using Bluetooth® wireless technology for
Servo, Autolock, or Reflectorless operation.
Set up Total Station Position –
Set up the total station and establish its position and
orientation on the site using the known point or arbitrary
location (also known as free station or resection)
methods.
Instrument Functions Menu-
Provides access to all total station specific functions and
settings in addition to calibration procedures for angle
collimation, tilt axis, and tracker collimation errors.
Recheck System Setup-
Check the current instrument setup on a known point
location.
Enter/Measure Control Points-
Edit and enter control point coordinates; measure new
control points.
Switch to GPS System-
Setup Access the GPS System Setup menu.

17. SCS900
Creating a Site

18. SCS900
Note – Always set the distance units correctly before taking a measurement or associating
a design with the site. All files that relate to a single site must be stored and operated with
the same units. Once a measurement is taken, or a design is selected, you cannot change
the units.

19. Starting the GPS base station
SCS900
Starting the GPS base station

20. Positioning the GPS base station
Located at a known or unknown point
Pick a point from the control point list
Set up on an unknown position
Enter its local coordinate
Enter its lat/long/height
Set up radio only
Positioning the GPS base station
Pick a point from the control point list
This method enables you to pick a control point at which the
base station is to be located from the control point file. The
control point can be selected from the map view or from the
list of control points. Place the base station at that specific
location before initiating the base station setup. Typically,
control points are established by the project surveyor. You can
obtain the coordinates directly from the surveyor, or from the
project documents.
Set up on an unknown position
This is probably the most commonly selected method. The base
station is established at a convenient location for the project,
where the antennas can be mounted high for optimum
performance and visibility of the sky. The best solution here is
to establish a T-Bar at which the GPS receiver and antenna can
repeatedly be placed in the same location each day,
eliminating possibilities for error. In this case,
when you start the base station, the GPS receiver carries out a
“Here” position using the GPS information to create a base
station location position. The GPS information determined
here is an Autonomous position and contains a position error
that will be computed and adjusted for as a part of the site
calibration process.
Enter its local coordinate
Entering a local coordinate for the base station location
enables you to manually enter a point coordinate as opposed
to getting it from the control point file. You can use this
method for quick topo measurements where the site will be
calibrated using a single-point calibration, or where the base station
will be located on a control point, which has a known local
coordinate location. Enter the coordinate data as northing,
easting, and elevation.
Enter its lat/long/height
Enter the base station’s latitude, longitude, and height when
placing the base station at a location at which those values are
precisely known, and one that is directly related to other site
positions through the GPS site calibration.
Set up radio only
Use this method once a base station is established on a site and
you need to change the radio channel or network number for
the base station radio, for example, because the site is
experiencing interference from a third-party crew operating
nearby on the currently selected radio channel or network
number.

21. Starting the GPS base station
AutoBase®
remembers how the previous setup was made
reconnects the components
selects the appropriate radio channel
network number
starts to transmit GPS positions
When using the SPS781/SPS881 Smart GPS antenna or the SPS751/SPS851
Modular GPS receivers, which use the AutoBase® technology, once a base station has been
established the first time, if nothing is changing between setups, you can simply set up the
receiver at the base station location and then switch it on. Using AutoBase technology, thereceiver reloads all appropriate data, makes all appropriate connections, and then starts to transmit corrections on the last used radio channel or network number. This eliminates
the need to use a controller with the software to set up the base station each day.
Note – If you want the SPS GPS (SPSx81 Smart GPS antennas, and the SPSx51 Modular
GPS receivers) to operate in Autobase mode, you must name each base station with a
different name, otherwise Autobase appears not to work.

22. Starting the GPS base station
Before you start the base station, ensure that you do the following:
Connect the controller to the receiver, if using a cable. Alternatively, you can make the connection using Bluetooth wireless technology from within the SCS900 software.
Turn on the controller.
Start the SCS900 software.
Create a new work order on a new site if not previously created.
Enter the control point coordinates for the project .
1. Connect the controller to the receiver, if using a cable. Alternatively, you can
make the connection using Bluetooth wireless technology from within the
SCS900 software.
2. Turn on the controller.
3. Start the SCS900 software
4. Create a new work order on a new site if not previously created
5. Enter the control point coordinates for the project

23. Setup Base To set up the base station System Setup Setup Base
Select Connection
Wireless
Cable

24. Connection Method Wireless Cable
connect through Bluetooth wireless technology
Cable
connect through a cable

25. Wireless Connection Scan for available Bluetooth devices
If the receiver has previously been used as a base station on this site, then the
SCS900 software first scans to see if the last used receiver is available through a
Bluetooth wireless connection. If found, the SCS900 software displays a message
asking if you want to connect to the last used receiver.
The SCS900 software connects to that receiver and enables you to proceed with the base station setup:

26. Correction Method Transmitting RTK Corrections
Via radio in the receiver
Via Trimble/PacCrest radio using cable
Via Trimble Bluetooth radio
Via a third-party radio
Via a cell phone
Via radio in the receiver –
the SPSx51 receiver as a base station, it is likely that you
will select the option shown for both 450 MHz and 900
MHz radio operations
Via Trimble/PacCrest radio using cable-
any receiver with an external TRIMMARK 3, PDL 450, or
HPB 450 radio for 450 MHz operations
Note – If you select this option, the software scans the
data controller serial ports to find a Trimble or PacCrest
PDL radio. Ensure that the radio is connected to either
Port 1 or Port 2 of the SPS GPS. To set the baud rate
settings for the PDL radio, from the main menu select
(4)Settings. Click More and then select (2) Radio Baud Rate
Via Trimble Bluetooth radio-
the SPSx81 GPS receiver as a base station for 900 MHz
radio operations and you are using the external SNB900
Radio
Via a third-party radio-
a third-party radio system excluding Pacific Crest
Via a cell phone-
a cell phone

27. Position the Base Located at a known or unknown point
Non-available Options are grayed out
Position the base
Options that are not available are grayed out. The above example shows:
– Option (1) is not available because no control points exist in the current
site.
– Option (2) is not available because the base station has not been established
on this site before.

28. Setup on unknown location
Option only if site has not yet been calibrated
Once a site has been calibrated:
Located at a known point
Control point in the calibration process
Established using the measure control point function
You can use this option only if the site has not yet been calibrated
Once a site has been calibrated, the base station must be located at a known point that
was either used as a control point in the calibration process, or that has since been
established using the measure control point function

29. Setup on unknown location
The software prompts you, noting that the base station should be set up in an
open location where the GPS antenna has a clear view of the sky (satellite
visibility)
Because the base station is being set up at an unknown location, the position
that is determined for the base station setup needs to be established as a control
point, so you need to enter a point name and code.
In this case, the point has been named “a1” and the code has been named “stn”.
This name and code is added to the control point file along with the measured
coordinates on completion of the site calibration process. The base station’s
point name is also transmitted over the radio so that as the rover connects to
the base station, it can check that the incoming corrections are from the correct
base station receiver.

30. Pick a point from the control point list
Method is most likely to be used
moving the base station from one location on site to a new location
site has been calibrated by a surveyor
known location is available only after you enter control point coordinates
This method is most likely to be used when moving the base station from one location
on site to a new location. To do this, the site will typically have been calibrated and the
receiver has to be established at a known point.
The method is also useful when the site has been calibrated by a surveyor, and you will
use the surveyor’s calibration instead of carrying out your own calibration. In this case,
you must locate the base station receiver at one of the surveyor’s control points.
Setting up the base station at a known location is available only after you enter control
point coordinates, which you can create either using the control point editor or by transferring a control point file from the
office software to the controller.

31. Enter its local coordinate
Known point
enter the base station location
This is another known point (known station) base station location method. Instead of
picking the point from the map view, you can enter the base station location as local
coordinates.

32. Enter its latitude, longitude, and height
Another known point
point is a known point
local site coordinate is not known
has been lost
This is another known point (known station) base station location method. Use this
method where the point is a known point but the local site coordinate is not known or
has been lost.
Instead of picking the point from the map view, you can enter the base station location
as WGS-84 latitude, longitude, and height. This information is known from the time
that the receiver was first set at this location, or from surveyor’s notes.
This method enables you to enter the latitude, longitude, and height for the point and
still tie the base station into an existing site calibration.

33. Completing the GPS base station setup
Antenna Type
GPS antenna from the list of antenna types.
The following steps are the same for whichever option you selected to position the
base.
In this example, an SPSx51 Modular GPS receiver is being used with an external GPS
antenna, so you must select the appropriate GPS antenna from the list of antenna
types. Selecting the correct antenna type is very important, especially if the base
station’s configuration is changed at any time to use an alternate receiver or antenna
type. This is because the antenna selection affects the height computed for the base
station location. In this example, the Zephyr Geodetic™ Model 2 antenna will be
selected, which is most commonly used as the base station antenna with the SPSx51
GPS receiver.

34. Base Antenna Height Antenna Height
computed elevation for the base station position
where the antenna height is measured
Enter the antenna height so that the computed elevation for the base station
position can be determined correctly.
If using a T-Bar setup, where the antenna will be placed at the same location in
both position and elevation each day, the antenna height can be entered as 0.0 m
(0.0 ft).
Select to where the antenna height is measured. Typically, the height is entered
as a measurement to the bottom of the antenna mount. However, various
options are available from the Measuring list. Again, the method of
measurement is important, since the software uses known dimensions of each
supported antenna to determine the correct elevation for the computed base
station location.

35. Radio Channel or Network
GPS receiver uses
Channels
Frequency
Radio network
Depending on which type of radio (450 MHz or 900MHz) is used, the GPS
receiver uses either channels and frequency (450 MHz) or the radio network
number (900 MHz) to determine on which frequency or network to transmit the
RTK corrections. For RTK operations to take place, the base station must
transmit, and the rover must receive data on the same channel or network
number. SCS900 first queries the rover receiver to determine the current radio
settings. In the example shown, the receiver is using 900 MHz radios, so network
numbers are shown.
Select the radio network number or channel on which the base station is to
transmit.
For 450 MHz radios, channel numbers are displayed rather than actual
frequencies such as MHz, so you need to have previously noted the actual
frequencies against the channel number in the radio so that all rovers can use
the same site frequency.
If you are using a PDL 450MHz radio and you previously selected to connect to
that radio (2Select Connection option), the software displays a list of the
channels (such as 1, 2, 3) that the radio has available.

36. Checking Channel/ Network
Skip
no-one else is working within radio range
make sure that no interference
save time
At this point the base station receiver is connected and tracking satellites, so the
number of satellites being tracked is now shown at the bottom of the screen:
Once set, the channel or network number selected is set to “receive” mode and
scanned for a short period to make sure that the channel/network is clear before
setting it to “transmit” mode and establishing the RTK correction stream. The
following message appears:

37. Base Station information
Set Up Base Complete
Base Station information
logged to the work order report file
hard copy record
re-established
Once the scan is completed, the receiver setup is complete, and the base station
information appears for you to check. The information is also logged to the work
order report file as a hard copy record of what was set up. This information can
be useful if the base station location has to be re-established for any reason.

38. Base Station Warnings
GPS receiver is not receiving any satellite signals
Loose cable between the receiver and the antenna
cable between the receiver and the antenna is damaged
switched on after a long period of no use
GPS antenna is obstructed
If the base station’s GPS receiver is not receiving any satellite signals from the
GPS antenna, the following warning message appears:
This message may be caused by one of the following:
– The cable between the receiver and the antenna is not tightly connected at
one or both ends.
– The cable between the receiver and the antenna is damaged.
– The receiver has just been switched on after a long period of no use, and
needs time to update its almanac and re-acquire satellites.
– The GPS antenna is obstructed and has no clear view of the sky.

39. SCS900
Site Calibrations

40. Types of site calibrations
Three types of calibration
A single-point calibration
A two-point calibration
A multi-point calibration
If points are suspect
continues to warn you
surveyor for the project to check and validate the control
check your equipment
level bubble on your GPS rod
the rod
tip of the rod
A single-point calibration
Used for short tasks or initial site measurements before control points have
been established for the project.
A single-point calibration involves measuring a single point location and
assigning that location an arbitrary site coordinate value such as northing=5000,
easting=2000, elevation=250. The calibration will orientate to GPS north. This
technique is often used for small site topographic measurements before
construction, or for measuring stockpiles. If the collected data will be required
later for ongoing project operations, Trimble recommends that you mark out
and measure a number of control points on the site. The control points can be
measured later in the true coordinate system for the project, so the initial
measurements can then be transformed onto the site coordinate system using
software such as the Terramodel® Field Data Module. Data collected using a
single-point calibration does not suffer from degraded accuracy; it simply will
not tie in with the site coordinate system and design once that becomes
available.
A two-point calibration.
Used where only two control points are available for calibration purposes. The
first point provides position; the second point provides orientation to a local site
coordinate system, which may not be aligned with true north.
A multi-point calibration
Used on nearly all construction projects to match the GPS system to the local
site control and design coordinates for the project. Multiple control points
spread around and across the jobsite are measured to provide an accurate
transformation computation that covers the entire project.
A site calibration can be created in the office using a map projection
Note – If many points are suspect and the software continues to warn you that the
calibration is out of tolerance, Trimble recommends that you get the surveyor for the
project to check and validate the control before proceeding with operations. You may also
want to check your equipment such as the level bubble on your GPS rod (to make sure that
it is correctly adjusted), the rod (to make sure that it is not bent), or the tip of the rod (to
make sure that it is not worn down and therefore giving height errors). You must keep the
pole, pole bubble, and pole tip well adjusted and maintained to guarantee the best results.

41. This is the GPS calibration!
Site Calibrations
This is the GPS calibration!
Local
North, East,
Elevation
WGS84
Lat, Long,
Height
Includes datum transformation, map projection, horizontal & vertical adjustment
Can select from library or DC file
The site calibration process involves measuring a
number of known control points in the local site
coordinate system using a GPS rover, allowing the
SCS900 software to create pairs of measured
latitude, longitude, height and known northing,
easting, and elevation values from which it can
derive a transformation from a GPS position to a
site coordinate system position.
The site calibration is stored in a DC file that
remains associated with the site. The DC file is
compatible with the Trimble Survey Controller™
software, so that the calibration data can be shared
if you are given a site calibration DC file from
surveyors working on the project who use other
Trimble equipment. The SCS900 software can also
export the site calibration to a CompactFlash card
as a CFG file that can be used in the Trimble
SiteVision or GCS900 machine control systems.

42. Plane Coordinate Systems
Mapping projections are used to represent positions on the curved surface of the earth as points on a flat surface or plane. Mapping projection surfaces used in surveying are designed to minimize the distortion that can occur when a curved surface is flattened.

43. Horizontal Adjustment
Rotation
Translation
Scale
After the WGS-84 positions have been transformed and projected as just discussed, there may still be some inconsistencies between
the grid coordinates produced from the GPS measurements and the grid coordinates that are accepted as true values for the respective points.
To resolve these inconsistencies a horizontal adjustment can be applied to the GPS grid coordinates. The best adjustment of survey data employs the principle of least squares. The horizontal adjustment is an unweighted least squares best fit of the coordinates for the points determined by GPS to the coordinates of the points accepted as true.
In the calibration, a grid coordinate obtained from GPS measurements is paired to a control grid coordinate for each calibration point. The result of the least squares best fit is a single set of parameters that describe how to make the GPS derived coordinates fit, as closely as possible, to the control
coordinates.
The parameters are:
• Rotation of the GPS coordinates
• Translation of the GPS coordinates
• Scale factor for the GPS coordinates

44. Horizontal Adjustment
= GPS observation
= Control Point
After the WGS-84 positions have been transformed and projected as just discussed, there may still be some inconsistencies between
the grid coordinates produced from the GPS measurements and the grid coordinates that are accepted as true values for the respective points.
To resolve these inconsistencies a horizontal adjustment can be applied to the GPS grid coordinates. The best adjustment of survey data employs the principle of least squares. The horizontal adjustment is an unweighted least squares best fit of the coordinates for the points determined by GPS to the coordinates of the points accepted as true.
In the calibration, a grid coordinate obtained from GPS measurements is paired to a control grid coordinate for each calibration point. The result of the least squares best fit is a single set of parameters that describe how to make the GPS derived coordinates fit, as closely as possible, to the control
coordinates.
The parameters are:
• Rotation of the GPS coordinates
• Translation of the GPS coordinates
• Scale factor for the GPS coordinates

45. Rotation
All of the horizontal points in the calibration are used to calculate a centroid (geographic center) about which a rotation of the GPS grid coordinates is applied. All of the observed GPS points in the project, even those not used in the calibration, will be rotated by the same angular amount. A minimum of two horizontal calibration point pairs are required to calculate a rotation parameter.

46. Translation
A translation moves all of the observed GPS coordinates in the same direction and by the same distance, so that they lie closer to the control
coordinates. The translation parameter will be applied to all of the observed GPS (WGS-84) positions in the project. A translation parameter will be calculated with as few as one horizontal point pair used in the calibration.

47. Scale
A scale factor is determined using a ratio of the true distances, calculated between horizontal control coordinates, and the distances calculated between the GPS grid positions for the same points. This ratio of these two distances is the scale factor. The scale factor is applied to all of the GPS coordinates to obtain the best possible fit to the control coordinates. At least two point pairs must be used in the calibration to calculate a scale factor.

48. Horizontal Residuals Residual
To perform the horizontal adjustment, at least three control points are needed. Each of these points must be observed with GPS as well as possess control coordinate values. Three points are required for the horizontal adjustment because it takes two points to derive the adjustment parameters and one additional point to provide a check on the fit obtained from those parameters. This check appears as residuals for each point in the
calibration.

49. Residuals Useful indicator Expected magnitude of a residual
Quality of the calibration
Control
Measurement
Expected magnitude of a residual
quality of the control points
field procedure
measurement methods
size of the site