System and method for using corrected signals from a global positioning system to perform precision survey

• US 7,110,762 B1
• Filed: 04/28/2004
• Issued: 09/19/2006
• Est. Priority Date: 09/15/2000
• Status: Expired due to Term

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Cameron, John F., Sellers, Mark D.
• Primary Examiner(s): Feild, Joseph
• Assistant Examiner(s): Afshar, Kamran
• Application Number:
  US10/833,380
• Time in Patent Office: 874 Days
• Field of Search: 455516-517, 455 62- 63, 455/456.1, 455/11.1, 455/562.1, 455/575.7, 4552261-2262, 455/180.1, 455/179.1, 455/176.1, 455/226.4, 455/161.1, 455/450, 455/434, 455/452.1, 455/509, 455/456, 455/515, 455/513, 342/357.08, 342/357.03, 342/357.09, 343/343, 343/790, 343/713, 343/860, 343/745, 701214-215, 701/204, 701/207
• US Class Current: 455/434
• CPC Class Codes: G01C 15/00 Surveying instruments or accessories not provided for in groups G01C1/00 - G01C13/00
• CPC Class Codes: G01C 15/06 Surveyors' staffs; Movable markers
• CPC Class Codes: G01S 19/35 Constructional details or hardware or software details of the signal processing chain

Abstract

In a differential global positioning system that includes one or more base stations and rover units, a system and method for including a radio modem transceiver in the rover units, and packaging several components, including the transceiver and a radio antenna in a single package, and possibly including re-chargeable batteries, a GPS receiver, and a GPS antenna in the package, to reduce the number of external electrical connections. Several of the components may be packaged into a survey range pole. GPS satellite correction information is transmitted from a base station in response to a request transmitted from the rover unit by means of the radio modem transceiver. Automatic channel selection is performed by the base stations to select a channel having low communication traffic. The rover units scan the available channels for valid GPS correction information and, in the event that more than one such channel is located, select the channel with the strongest signal.

Claims

1. A base station in communication with a rover unit for use in a Differential Global Positioning System (DGPS), comprising a radio modem transmitter or transceiver having a plurality of pre-defined communication channels, a GPS satellite receiver, and channel selection means for automatically determining which of its pre-defined communication channels is most open to RF traffic and selecting said channel, wherein the communication channels include a Received Signal Strength Indicator (RSSI) and the channel selection means includes an algorithm that measures the RSSI value for each pre-defined communication channel and includes instructions for re-measuring the RSSI values of the pre-defined channels in response to a predefined increase in communication traffic, wherein the openness to transmission of a valid GPS correction information is based on the amount of communication traffic on the channels.

2. A base station of claim 1, further comprising means for manually overriding the selected channel.

3. A base station of claim 1, further comprising an internal processor, wherein an analog signal from the RSSI is converted to digital form by an A-D converter for use by the processor in selecting a channel.

4. A base station of claim 1, further comprising means for controlling the transmitting power output of the radio modem transmitter or transceiver.

5. A rover unit for use in a Differential Global Positioning System (DGPS), comprising a radio modem transceiver, and a radio antenna, wherein the radio modem transceiver and radio antenna are packaged in a single housing with the radio antenna forming a tubular structure around the radio modem transceiver, further comprising a GPS satellite receiver attachable to the housing, wherein the radio modem transceiver and radio antenna are arranged in a stacked configuration in the same housing.

6. A rover unit of claim 5, further comprising a power supply packaged into the same housing.

7. A rover unit of claim 5, wherein the radio modern transceiver and radio antenna are housed in a housing that is transparent to radio frequencies.

8. A rover unit of claim 5, wherein the radio antenna is mounted on an outer surface of the housing or is formed integrally with the housing.

9. A rover unit of claim 5, wherein the radio modem transceiver and power supply are packaged in a survey range pole and the antenna is packaged in the range pole or mounted on an outer surface of the pole or formed integrally with the pole.

10. A rover unit of claim 9, wherein the survey range pole includes a first section and a second section that are releasably connectable end to end.

11. A rover unit of claim 9, wherein the power supply includes at least one rechargeable battery.

12. A rover unit of claim 11, further comprising battery charging electronics packaged in the survey range pole.

13. A rover unit of claim 9, wherein the pole includes a coupling for connecting a GPS satellite receiver system to the pole.

14. A method for performing differential global positioning involving a base station and a rover unit, comprising the steps of:

selecting at the base station from a set of pre-defined communication channels, a channel that is most open for the transmission of data and

transmitting GPS correction information on the selected channel and scanning at the rover unit a set of pre-defined communication channels to locate a channel which is carrying valid GPS correction information,

further comprising the step of returning to the scanning step when the transmission of the valid GPS correction information ceases on a selected channel, wherein the openness to transmission is based on the amount of communication traffic on the channels.

15. A method of claim 14, wherein the GPS correction information is sent in response to a request from the rover unit.

16. A method of claim 14, further comprising a step of reselecting a channel at the base station in response to pre-defined conditions.

17. A method of claim 16, wherein one of the pre-defined conditions is that the previously selected channel experiences a pre-defined increase in communication traffic.

18. A method of claim 14, further comprising the step of adjusting the power at which the GPS correction information is transmitted, in response to regional requirements.