用C#開發(fā)GPS Reader(附源文件,For WinCE)

2010-08-28 10:50:27來源:西部e網(wǎng)作者:

C#   GPS Reader

Source Code: http://www.paul-abraham.com/ArticleDP/GPSReader.zip

In this brief article, I like to show you how to read data from a GPS mouse and persist it in a database. You need a GPS Mouse, Visual Studio and SqlServer  to follow this article.

Recently, I need to  find out  which  percentage  I use my firm car  for  private  trips. So, I have programmed a log book to record   every trip  and  I like discuss the prototype of the log book application.

Follow subsequent steps in order to install the  example application

  1. Download the  zip file
  2. Create a database  with the name “GPS”   and  run  the  GPSReader\Publish\CreateDB.sql  script to create table and store procedures
  3. Adjust the  “l(fā)ocalConnection”  key   on  the  App.config file which is used to connect to the SqlServer
  4. Connect the GPS mouse with computer. Normally, GPS devices have USB interface which  writes  data into a virtual com port. You can  find out the particular port  in the Device Manager under the section Ports(COM&LPT)
  5. compile the application(compiling order: BEC,DAT,SerialPort,BLT and GPSReader)  , select the appropriate virtual com port and start

If  you are curious to know how does GPS  work ,then  please refer following links

  1. http://www.pocketgps.co.uk/howgpsworks.php
  2. http://scign.jpl.nasa.gov/learn/gps2.htm
  3. http://www.american.edu/academic.depts/cas/mathstat/People/kalman/pdffiles/gps.pdf (very good article)                                                                                                             

GPS  devices offer  data  in form of  sentences which are defined by  NMEA-0183  protocol. There are lot of sentences in the NMEA protocol and it is infeasible to save the whole emitted information in a database, therefore we going deal with only one sentence. The $GPRMC  sentence  (Recommended minimum specific GNSS data) contents necessary minimum information for navigation purposes.  

Example (signal not acquired): $GPRMC,235947.000,V,0000.0000,N,00000.0000,E,,,041299,,*1D
Example (signal acquired): $GPRMC,092204.999,A,4250.5589,S,14718.5084,E,0.00,89.68,211200,,*25

Field

Example

Comments

Sentence ID

$GPRMC

 

UTC Time

092204.999

hhmmss.sss

Status

A

A = Valid, V = Invalid

Latitude

4250.5589

ddmm.mmmm

N/S Indicator

S

N = North, S = South

Longitude

14718.5084

dddmm.mmmm

E/W Indicator

E

E = East, W = West

Speed over ground

0.00

Knots

Course over ground

0.00

Degrees

UTC Date

211200

DDMMYY

Magnetic variation

 

Degrees

Magnetic variation

 

E = East, W = West

Checksum

*25

 

Terminator

CR/LF

 

Please refer the following link for further GPS sentences.

http://www.commlinx.com.au/NMEA_sentences.htm

The heart of the application is the BLGPSReader class.  This  class   has a timer and  its callback method (void CollectData(object oState))  will collect   and persist   received  data  in a  particular time tact  .

/// <summary>

/// Callback from tGPSTimer Timer

/// </summary>

/// <param name="oState"></param>

protected void CollectData(object oState)

{

try

{

if(this.gpsState.State == StateEnum.Receive)

{

 

// read from gps device

string strRead=this.serialPort.ReadAvailable();

strRead=strRead.Trim();

if(strRead!=String.Empty)

{

// add to extractor

this.oExtractor.Add(strRead);

string strGPSSentence=String.Empty;

// if a full sentence available, then notify clients and store in data base

while(this.oExtractor.Get(out strGPSSentence)==true)

{

this.NotifyClients(strGPSSentence);

 

WaitCallback oWaitCallback=new WaitCallback(this.blPersistManager.Persist);

BEC.PersistContent oPersistContent = new BEC.PersistContent(strGPSSentence,this.strMovObjId);

ThreadPool.QueueUserWorkItem(oWaitCallback,oPersistContent);

 

}

 

}

 

} //if(this.gpsState.State == StateEnum.Receive)

 

}

catch(Exception oException)

{

string strTest=oException.Message;

}

finally

{

if((this.gpsState.State != StateEnum.Stop))

{

this.tGPSTimer.Change(this.nReceiveInterval,0);

}

}

 

}

I am using  SerialPort class, which you can download from the link http://www.gotdotnet.com/Community/UserSamples/Details.aspx?SampleGuid=b06e30f9-1301-4cc6-ac14-dfe325097c69, to read the GPS sentence from a specified com port.

An instance of   GPSSentenceExtractor class is used to collect received  partial sentence and you can retrieve full sentences using  its Get(out strGPSSentence) method. We are using  ThreadPool  to persist  GPS sentence so that  this persisting process won’t  block  receiving process.

As you can see in the finally block, we change  the timer to  call this method again which ensures that this method  won’t be  executed  simultaneously. I am using my own  data access tier ( http://www.paul-abraham.com/ArticleDP/DATier.htm ) to persist  GPS data.

原文:http://www.paul-abraham.com/ArticleDP/gps.htm

關(guān)鍵詞:C#