EAS-591T – Space Geodetic Measurements of Active Crustal Motions

 

LAB 11

Surveying with GPS: field measurements

Return:    Log sheet

               30 minute raw and rinex files

               mp1 and mp2 plots

Basic operation for Ashtech MicroZ receivers: complete ALL steps in the order indicated

Tripod setup

  1. Attach tribrach to tripod (screw).
  2. Attach leveling device to tribrach.
  3. Center and level the tribrach above the mark. Take as much time as needed to make it absolutely perfect.
  4. Secure the tripod legs with stones or sand/gravel bags (even if it’s not windy).

Antenna setup

  1. Attach the adapter srcew to the bottom of the antenna
  2. Connect the antenna cable to the antenna.
  3. Place the antenna delicately on the leveling device.
  4. Orient  the antenna to geographic north using the compass.
  5. Secure the antenna in place.
  6. Measure the height of the antenna at 3 locations 120° apart as indicated below:




 

  
  
  
  
 

 

  
  
  
  

   

    
    

    
Choke ring antenna:

    
slant height measured from mark to lower edge of ground plane

    
 

    

    		
   

  

   		
 

 

  
  
  

   

    
    

    
Geodetic II or II antennas:

    
slant height measured from mark to top of ground plane

    

    		
   

  

   		
 

 

  
 




 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


  1. Unroll the cable from the antenna to the receiver without twisting it.
  2. Protect the cable from being stepped on.
  3. Connect  the antenna cable to the receiver.

Running the receiver

 

 

  1. Connect power to receiver.

Ž  If A.C. power is available, connect the transformer to AC (check AC voltage and compatibility with transformer input) and to the receiver. ALWAYS connect a backup battery to the second power port.

Ž  If no A.C. power available at the site, connect 1 battery to the receiver while charging the other one (hotel room, private house, restaurant, etc). Switch batteries after each session or if voltage too low (use the second power port to avoid power disruption).

Ž  If solar panels are available connect them to the battery in parallel and connect the battery to the receiver. Two 30 W panels will give enough power on a sunny summer day for the receiver and will charge the battery.

  1. Turn the receiver ON (actually, it turns itself on as soon as you connect power).
  2. Connect receiver to PC (serial port = RS-232), use either of the 2 serial ports.
  3. Start MicroManager.
  4. Configure the receiver in the following order:

1.      “Receiver/Settings/Recording controls”:

q       30s  / 1SV  / 10s el / data mode 0

2.      “Receiver/Settings/Project information”:

q       4 letter site code.

q       Antenna height, average of 3 measurements.

q       Antenna radius (0.1905) and offset (0.035)

q       Session number (1)

q       Date

q       Serial numbers for receiver and antenna

q       Operator’s intials

  1. Verify the following items:

1.      “View/Receiver information”:

q       Verify that all is correct

2.      “Receiver/Files”:

q       Is there sufficient free memory for the session?

q       Is a new file created with the correct site name?

q       Is the time of the file (last data recorded) the current time?

q       Is the size of the file increasing with time?

3.      “View/Receiver status/Channel summary”:

q       Are satellites visible (6 to 10) and recorded ("LK")?

q       Is the receiver is recording data?

Filling out the log sheet

Fill out ALL items (even if you don’t understand their significance or if they appear meaningless to you). Particularly important are the following:

1.      The site NAME

2.      The DAY

3.      The ANTENNA HEIGHT

4.      The ANTENNA MODEL

During the session

Verify regularly (every 1 or 2 hours) the following items:

q       Is the size of the data file increasing?

q       Is the size of the memory left decreasing?

q       Is the time of the file (last data recorded) the current time?

q       Are the satellites indicating locked status "LK"?

q       BATTERY VOLTAGE

Ending the session

The session ends at 23:59 UTC. The data file in the receiver has to be closed before downloading. There are 3 possibilities for closing a data file and ending a session:

1.      Turn the receiver off. This will close the current file in the receiver.

2.      Close the session “softly” without turning the receiver off

3.      If a session was programmed (see the “programming sessions” section below), there is nothing to do, the session will be closed at the specified time.

Downloading the data

  1. Turn the PC power ON.
  2. Using Window’s Explorer or any similar utility:

7 Go to GPS\DATA\RAW

7 Make a directory called ‘day’ (= day of year, 001 for January 1st to 365 for Dec. 31st)

  1. Turn GPS receiver on (if it was not already on).
  2. Connect the Personal Computer (PC) to the receiver with the serial cable (either port).
  3. Download the data:

7 Open MicroManager on the computer

7 Go to “Receiver/Files”

7 Select “Decompress to Ashtech format B, E, S”

7 Unselect “Convert to RINEX”

7 Select the files that you want to download.

7 Start downloading

Errors may occur during file download, they are indicated on the screen with the download progress. Most of the time, the program will recover these errors and the number of errors and number of recovered errors will be equal. This is fine, but the download time will increase. If the number of errors is too high (say, greater than 100) or if an error message appears (such as “Data type error”), use a  lower baud rate (“Change communication parameters” menu).

7 Exit MicroManager.

  1. Verify that the data has been downloaded. Using Window’s Explorer or a similar utility, verify that:

q       The B-, E-, and S-files were copied to the hard disk.

q       The size of the data files is correct.

22 hours of data recorded at 30 seconds with a 10° elevation mask at a site with no sky obstruction on a Z12 receiver produce a B-file of about 2.1 Mb, an E-file of about 40 Kb, an S-file of about 0.5 Kb.

q       The name of the data files is correct.

Each session creates 3 files:BsiteNYR.day, SsiteNYR.day, EsiteNYR.day, where YR = last 2 digits of year, N = session number (A, B, … or 1, 2, …), day = day of year of the last recorded data. If the file was closed at 0 hours 0 min 30 sec instead of  23 hours 59 min 30 sec, the day number will appear to be incorrect in the name of the file (it will be day+1). This is not a problem, just put the data files in the correct directory, then rename them with the correct day number.

  1. Fill out the logsheet.
  2. Copy the downloaded files from the hard disk to a diskette.

7 Compress the B-, E-, and S- files into a single ZIP file that you call siteday.zip 7 Copy the file siteday.zip to a diskette.

7 Check that the data has been transferred to trhe diskette (verify size of files)

< Write protect the diskette.

< Label the diskette with the site and day, antenna height and antenna type.

  1. Download the data again from the receiver to the hard disk

7 Download the data in GPS\DATA\BACKUP

7 Compress and copy the files on a new diskette, write protect and label it.

RINEX translation and Quality control

  1. Open a DOS (= “command prompt”) window.
  2. Type:

cd GPS\DATA\RINEX

mkdir DAY                  [with DAY = day of year]

cd DAY

  1. To create RINEX observation and navigation files, type (on one line):

teqc -ash d -O.int 30 -O.obs L1L2C1P1P2 -O.at "ASHTECH_CR" -O.sl SLANT 0.3810 –0.035 +nav ssssddd0.yyn ..\..\RAW\ddd\bssssyya.ddd >! ssssddd0.yyn

 

[with:    slant = antenna slant height

            ssss = site name (4 character)

            ddd = day of year

            yy = year (last 2 digits) ]

  1. To quality check the RINEX data, use the program that you wrote for lab3!
  2. Or:

teqc +qc ssssddd0.yyn > sssddd0.out

Edit ssssddd0.out or ssssddd0.yyS

Run qcview: qcview ssssddd0.mp2 ssssddd0.mp2 -nosquare