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

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

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.

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

Good or Bad

SCS900 Starting SCS900

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.

SCS900 Main Menu Structure

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).

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” emails.

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 emails can notify users of movement outside of the set tolerance.

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.

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” email 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.

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.

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.

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.

SCS900 Creating a Site

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.

Starting the GPS base station SCS900 Starting the GPS base station

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.

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.

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

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

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

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:

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

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.

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

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.

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.

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.

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.

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.

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.

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 459.75 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.

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:

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.

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.

SCS900 Site Calibrations

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.

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.

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.

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

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

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.

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.

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.

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.

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