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2: GPS Overview

GPS Overview

This chapter describes the various modes of operation and features 
of your Crescent A100 receiver and internal sensors.

For your convenience, both the GPS and differential correction of 
the Crescent A100 are pre-configured. The receiver will work out of 
the box, and for most applications, little user set up is necessary. 
When powered for the first time, the Crescent A100 will perform a 
“cold start,” which involves acquiring the available GPS satellites 
in view and the SBAS differential service.

GPS Operation

The GPS engine is always operating, regardless of the DGPS mode 
of operation. The following sections describe the general operation 
of the Crescent A100’s internal GPS engine.

Automatic Tracking - 

The GPS engine within the Crescent A100 automatically searches 
for GPS satellites, acquires the signals and manages the navigation 
information required for positioning and tracking. This is a hands-
free mode of operation.

Receiver Performance - 

The Crescent A100 works by finding four or more GPS satellites in 
the visible sky and uses the information those satellites provide to 
compute an appropriate position (typically within 

 

2-3 meters). Since there is some error in the GPS data calculations, 
the Crescent A100 also tracks a differential correction. The Crescent 
A100 uses these corrections to improve its position to less than 1 
meter (3 feet) (see 

 

Table B-5: GPS sensor specifications in the appendix).

875-0163-000 (Crescent A100).book  Page 20  Tuesday, November 13, 2007  11:29 AM

Summary of Contents for Crescent A100

Page 1: ...Crescent A100 User Guide Part No 875 0163 000 Rev C1 ...

Page 2: ...y form or by any means electronic mechanical magnetic optical chemical manual or otherwise without the prior written permission of Hemisphere GPS Inc TRADEMARKS Hemisphere GPS and the Hemisphere GPS logo Satloc and the Satloc logo Mapstar Air Star Outback Guidance and eDrive are trademarks of Hemisphere GPS Other trademarks are the properties of their respective owners NOTICE TO CUSTOMERS Contact ...

Page 3: ...875 0163 000 Crescent A100 book Page 2 Tuesday November 13 2007 11 29 AM ...

Page 4: ...tely of any claimed defect Repairs shall be made through a Hemisphere GPS approved service center only Exclusions Hemisphere GPS does not warrant damage occurring in transit or due to misuse abuse improper installation neglect lightning or other electrical discharge or fresh salt water immersion of Products Repair modification or service of Hemisphere GPS products by any party other than a Hemisph...

Page 5: ...ITY OF SUCH DAMAGES WITHOUT LIMITING THE FOREGOING HEMISPHERE GPS SHALL NOT BE LIABLE FOR ANY DAMAGES OF ANY KIND RESULTING FROM INSTALLATION USE QUALITY PERFORMANCE OR ACCURACY OF ANY PRODUCTS Governing Legislation To the greatest extent possible this warranty shall be governed by the laws of the State of Arizona In the event that any provision hereof is held to be invalid by a court of competent...

Page 6: ...ed Pulse Output 3 CAN 4 Installation 5 Cable Interface 6 Extension Power Data Cable 7 Crescent A100 Placement 7 Mounting the Crescent A100 10 Powering the Crescent A100 13 Connecting the Crescent A100 to External Devices 15 Environmental Considerations 18 875 0163 000 Crescent A100 book Page i Tuesday November 13 2007 11 29 AM ...

Page 7: ...S Overview 20 GPS Operation 20 Differential Operation 21 Appendix 25 A Troubleshooting 26 B Specifications 28 D Crescent A100 Accessories 32 E Surface Mount Template 35 875 0163 000 Crescent A100 book Page ii Tuesday November 13 2007 11 29 AM ...

Page 8: ...nstallation Features Installation Mounting the Crescent A100 Powering the Crescent A100 Connecting Crescent A100 to External Devices 875 0163 000 Crescent A100 book Page 1 Tuesday November 13 2007 11 29 AM ...

Page 9: ...and EGNOS signals The Crescent A100 provides sub meter performance with50 centimeter accuracy 95 of the time This chapter provides information on the following Features Installation Mounting the Crescent A100 Powering the Crescent A100 Connecting the Crescent A100 to external devices 875 0163 000 Crescent A100 book Page 2 Tuesday November 13 2007 11 29 AM ...

Page 10: ...erface protocol RTCM SC 104 and upgrading firmware See the general GPS technical reference at www hemispheregps com for more detailed information LED The Crescent A100 uses one tri colored LED Red indicates the power is on Amber indicates a GPS lock Flashing green indicates DGPS is being acquired Green indicates a DGPS solution Radar Simulated Pulse Output The radar simulated pulse output provides...

Page 11: ... Crescent A100 supports a selection of NMEA 2000 messages that can be broadcast on a CAN bus Table 1 1 provides a listing of the NMEA 2000 commands that are used Note Pin 12 does not have any form of isolation or surge protection You are STRONGLY encouraged to incorporate some form of isolation circuitry into your supporting hardware if you wish to utilize the Speed Radar Pulse output Table 3 1 NM...

Page 12: ... of using Hemisphere GPS e Dif and L Dif technology Figure 1 1 provides a front view of the deutsche connector receptacle s numbering Figure 3 1 Deutsche connector receptacle numbering Table 1 2 provides the Deutsche connector s pin outs Table 3 2 Deutsche connector s pin outs Pin Out Function 1 Manual mark in 2 TxB 3 RxB 4 CAN high 5 10 8 12 7 6 9 1 2 11 3 4 875 0163 000 Crescent A100 book Page 5...

Page 13: ...ension cable is damaged in the field it can be replaced without returning the complete Crescent A100 system Other power cables are available as accessories to fit a wide variety of applications See Appendix E for a list of Crescent A100 accessories 5 Signal Ground 6 TxA 7 One PPS 8 RxA 9 CAN low 10 Power in 12 V 11 Power ground 12 Speed out Table 3 2 Deutsche connector s pin outs Pin Out Function ...

Page 14: ...s Do not run the extension cable through door or window jams Keep the cables away from rotating machinery Do not bend excessively or crimp the cables Avoid placing tension on the cables Remove unwanted slack from the extension cable at the receiver end Secure along the cable route using plastic wraps Crescent A100 Placement Placement of the Crescent A100 is crucial to the system s operation The GP...

Page 15: ...are not masked by obstructions which can potentially reduce system performance To place the Crescent A100 1 Mount the Crescent A100 on or as close to the center of your point of measurement 2 Position the Crescent A100 as high as possible Figure 1 2 on page 9 shows the ideal location to place the Crescent A100 on a vehicle 875 0163 000 Crescent A100 book Page 8 Tuesday November 13 2007 11 29 AM ...

Page 16: ...Crescent A100 User Guide 9 Figure 1 2 Crescent A100 placement on a vehicle 875 0163 000 Crescent A100 book Page 9 Tuesday November 13 2007 11 29 AM ...

Page 17: ...bond the metal disc to the desired mounting location if there are no metal surfaces To use the metal disc and foam adhesive 1 Clean and dry the mounting surface on the vehicle 2 Remove the backing from one side of the foam adhesive and press the metal plate onto the mounting surface on the vehicle 3 Remove the backing from the other side of the foam adhesive 4 Press the metal plate onto the mounti...

Page 18: ...A100 1 Photocopy or remove Appendix E and use its line drawing as a template to plan the mounting hole locations 2 Mark the mounting hole centers as necessary on the mounting surface 3 Place the Crescent A100 antenna over the marks to ensure that the planned hole centers agree with the true hole centers then adjust 4 Use a center punch on the hole centers in order to guide the drill bit 5 Drill th...

Page 19: ...e and into the antenna Pole Mount The center thread of the Crescent A100 is 5 8 inches for compatibility with a survey pole not included Warning Install the Crescent A100 only hand tight Damage resulting from overtightening the Crescent A100 is not covered by warranty 875 0163 000 Crescent A100 book Page 12 Tuesday November 13 2007 11 29 AM ...

Page 20: ...d be continuous and clean Refer to Table B 1 Power specifications in the Appendix for power requirements The Crescent A100 features reverse polarity protection to prevent excessive damage if the power leads are accidentally reversed With the application of power the Crescent A100 will automatically proceed through an internal start up sequence however it will be ready to communicate immediately No...

Page 21: ...e you are in the world Note The Crescent A100 can take up to five minutes for a full ionoshperic map to be received from SBAS Optimum accuracy will be obtained once the Crescent A100 is processing corrected positions using complete ionospheric information 875 0163 000 Crescent A100 book Page 14 Tuesday November 13 2007 11 29 AM ...

Page 22: ...ering for the extension cable s DB 9 socket connector female The associated numbering for the plug connector male is a mirror reflection of the scheme shown in figure 1 4 Figure 1 4 DB 9 socket numbering Table 1 3 on page 16 provides the pin configuration for communication through the serial ports Note For successful communication the baud rate of the Crescent A100 serial ports must be set to matc...

Page 23: ...ound Table 3 4 DGPS Application 1 SBAS WAAS EGNOS etc Application 2 e Dif unsubscribed Table 3 5 Serial port settings Serial port Baud Rate Data bits Parity Stop bit Interface level Serial port A and B 4800 9600 19200 57600 8 None 1 RS 232C Table 3 6 GPS message output options GPS message Update rate Max DGPS age Elevation mask Hemisphere GPS Binary NMEA 0183 NMEA 2000 CAN From 1 Hz to 20 Hz 259 2...

Page 24: ...2000 commands NMEA 2000 message Updates rates GNNSPositionData 1 Hz GNNSPositionRapidUpdate 20 Hz with updates based on the subscribed rate i e every other message will be a copy of the previous on a 10 Hz receiever NMEACogSogData 20 Hz with updates based on the subscribed rates i e every other messages will be a copy of the previous on a 10 Hz receiver Note The changes you make to the Crescent A1...

Page 25: ... withstand various outdoor environments However there are specific environmental limits that you should meet when storing and using the Crescent A100 See Table B 4 Environmental specifications in Appendix B 875 0163 000 Crescent A100 book Page 18 Tuesday November 13 2007 11 29 AM ...

Page 26: ...2 GPS Overview GPS Operation Differential Operation 875 0163 000 Crescent A100 book Page 19 Tuesday November 13 2007 11 29 AM ...

Page 27: ...general operation of the Crescent A100 s internal GPS engine Automatic Tracking The GPS engine within the Crescent A100 automatically searches for GPS satellites acquires the signals and manages the navigation information required for positioning and tracking This is a hands free mode of operation Receiver Performance The Crescent A100 works by finding four or more GPS satellites in the visible sk...

Page 28: ...to calculate the geographic location Reception of any four or more of these signals allows a GPS receiver to compute 3 dimensional coordinates Differential Operation The Radio Technical Commission of Marine services RTCM has a differential service intended for correction services This includes the Space Based Augmentation Systems SBAS such as the Wide Area Augmentation System WAAS and the European...

Page 29: ...us on other aspects of differential operation without the need to tune the receiver The Crescent A100 features two channel SBAS tracking that provides an enhanced ability to maintain a lock on a SBAS satellite when more than one satellite is in view This redundant tracking approach results in more consistent tracking of a SBAS signal when in an area where signal blockage of a satellite is possible...

Page 30: ...computes a differential correction The user can operate for unlimited time and provide good relative accuracy Alternatively the operator can regularly update e Dif to maintain absolute accuracy typically less than 1 meter over 40 minutes 875 0163 000 Crescent A100 book Page 23 Tuesday November 13 2007 11 29 AM ...

Page 31: ...24 2 GPS Overview 875 0163 000 Crescent A100 book Page 24 Tuesday November 13 2007 11 29 AM ...

Page 32: ...Appendix Troubleshooting Crescent A100 Specifications Network Crescent A100 accessories Surface mount template 875 0163 000 Crescent A100 book Page 25 Tuesday November 13 2007 11 29 AM ...

Page 33: ...estrictions imposed by power source maximum is 250 mA No data from Crescent A100 Check receiver power status LED Check integrity and connectivity of power and data cable connections The volume of data requested to be output by the Crescent A100 could be higher than what the current baud rate supports Try using 19 200 or higher as the baud rate for all devices No GPS lock Check integrity of cable c...

Page 34: ... Check integrity of cable connections Verify Crescent A100 s unobstructed view of the sky Check SBAS visibility map Table A 1 Troubleshooting Problem Possible solution 875 0163 000 Crescent A100 book Page 27 Tuesday November 13 2007 11 29 AM ...

Page 35: ...t voltage 7 36 VDC Power consumption 2 W 12 VDC typical Current Consumption 150 mA 12 VDC typical Power connector Cable mount environmentally sealed Table B 2 Mechanical specifications Item Specification Height 54 7 mm 2 2in Width 129 5 mm 5 1 in Weight 0 66 kg 1 45 lbs Mounting Options Magnetic mount Fixed mount low or high pole 875 0163 000 Crescent A100 book Page 28 Tuesday November 13 2007 11 ...

Page 36: ...col NMEA 0183 SLX binary and NMEA 2000 Ground speed output Range 0 8 322 Km h 0 5 200 mph Signal Opto isolated pulse out Frequency Conversion 94 Hz m s 28 65 pulse per foot traveled Event mark output HCMOS active low falling edge sync 10 k ohm 10 pF load Table B 4 Environmental specifications Item Specification Operating temperature 30 C to 70 C 22 F to 158 F Storage temperature 40 C to 85 C 40 F ...

Page 37: ...logy during differential signal outage Channels 12 channel parallel tracking 10 channel when tracking SBAS Update rate 1 20 Hz positions Horizontal accuracy 0 6 m 95 confidence DGPS 2 5 m 95 confidence autonomous Differential Options SBAS e Dif L Dif SBAS Tracking 2 channel parallel tracking Start up time 60 s no almanac and RTC Satellite Reaquisition 1 s Table B 4 Environmental specifications Ite...

Page 38: ...atellites in view satellite geometry baseline length for local services and ionspheric activity Depends on multipath environment number of satellites in view satellite geometry and ionspheric activity 875 0163 000 Crescent A100 book Page 31 Tuesday November 13 2007 11 29 AM ...

Page 39: ...ation 875 0163 Crescent A100 owner s manual 875 0066 Warranty Table D 3 Crescent A100 cable accessories Part Number Cables 051 0129 Cable Crescent A100 power single port DB9 3 m 10 ft 051 0130 Cable Crescent A100 power dual port DB 9 3 m 10 ft 051 0132 Cable Guidance console port single port DB9 5 m 15 ft 051 0133 Cable adaptor converts 051 0132 guidance console port to a speed port 875 0163 000 C...

Page 40: ...rette lighter adapter extension 91 m 3 ft 054 0037 Cable power to AC adapter 1 83 m 6 ft 054 0038 Cable power cable 91 m 3 ft extension Table D 4 710 0052 A Series antenna magnetic mounting kit Part number Mounting accessories 478 0006 000 Black magnet mount 601 0003 005 Zinc disc 675 1022 000 Screw 5 8 Hex 683 0001 007 Tape 683 0001 008 Foam pad Table D 3 Crescent A100 cable accessories Part Numb...

Page 41: ...34 Appendix This page is intentionally left blank 875 0163 000 Crescent A100 book Page 34 Tuesday November 13 2007 11 29 AM ...

Page 42: ... E Surface Mount Template The following template should be used to plan for the location of the mounting holes used when surface mounting the Crescent A100 875 0163 000 Crescent A100 book Page 35 Tuesday November 13 2007 11 29 AM ...

Page 43: ...36 Appendix This page is intentionally left blank 875 0163 000 Crescent A100 book Page 36 Tuesday November 13 2007 11 29 AM ...

Page 44: ...www hemispheregps com e mail info hemispheregps com ...

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