MC-GPS
Frequently Asked Questions

If you have a a question or technical issue that is not addressed by this section, please contact us at support@cmtinc.com

 

MC-GPS Frequently Asked Questions

General Information
Q1 How long can I collect data with a 3 MB RAM Disk?
Q2 How long should my MC-GPS battery last in the field before it needs to be recharged?
Q3 How long should my MC-GPS battery last before it needs to be replaced?
Q4 How can I tell if my MC-GPS battery needs to be replaced?
Q5 What is the proper procedure for changing my MC-GPS receiver battery in the field?
Q6 What is the appropriate care and maintenance of my MC-GPS batteries?
Q7 Can I use an external antenna with my MC-GPS?

Satellite Tracking
Q8 The Tracking Status Indicator always shows "STS", "IAC" or "INS". How can I make it go to "N3Dx" mode?
Q9 Why does my MC-GPS stay in "TRK" mode even when I am tracking 4 or more satellites?
Q10 Why does my MC-GPS stay in "N2Dx" mode even when I am tracking 4 or more satellites?
Q11 I have an RTCM device (e.g., Coast Guard Beacon) attached to my MC-GPS, but the Tracking Status indicator never goes into "N3Cx" mode. Why?

GPS Data Collection Issues
Q12 How can I collect a point feature (like a sign) in the midst of collecting a line (like a road) or an area (like a tract)?
Q13 How do I set up my MC-GPS as a Base Station?
Q14 How can I get real-time differential correction in the field with my MC-GPS?
Q15 How far can I be from a Base Station and still get accurate differential corrections?
Q16 How can I optimize my data collection when I am in a city's downtown area or in a canyon?
Q17 Does rain affect data collection?
Q18 Why does my MC-GPS go in an out of Navigating or Featuring mode when I am collecting data?
Q19 How accurate is the MC-GPS at locating one's position?

Hardware Issues
Q20
How do I reset my MC-GPS?
Q21 Why did my MC-GPS hang up when I tried to open or create a Job?
Q22 Does my MC-GPS need any maintenance if I don't plan to use it for a month or more?
Q23 I received a "Can't write file" error in the middle of my GPS Job. What should I do?
Q24 After using my MC-GPS for a while under the sun, the display becomes too dark to read. What should I do?
Q25 I received a "Not enough memory. Part of it plotted" error when I tried to plot a Job. What should I do?
Q26 I received a "DISK FULL" message in the Featuring screen while storing a Feature. What should I do?
Q27 After I reset the MC-GPS, I get a "Low Power" message. What should I do?

Formatting Issues
Q28 What are the signs that my MC-GPS needs to be reformatted?
Q29 What is the drive configuration of the MC-GPS?
Q30 How do I format my MC-GPS?
Q31 How do I format the RAM Disk?
Q32 How do I "break out" into the OS from the splash screen?

 

 Q1  How long can I collect data with a 3 MB RAM Disk?

      
An MC-GPS with a 3MB RAM disk will store more than 24,000 point features, which is often enough for a day of work. However, you can fill a 3 MB RAM Disk with GPS data in about 7.5 hours when you continuously log a line or area feature. If your application will involve collecting line or area features for long periods of time you may want to consider 5 MB or 8 MB of RAM for data storage.
    

 

 Q2  How long should my MC-GPS battery last in the field before it needs to be recharged?

      
The MC-GPS data collector batteries (system battery) should last above 10 hours before recharging is necessary. The field-replaceable GPS engine battery should give 4-5 hours of continuous use before requiring recharging.
        

   

 Q3  How long should my MC-GPS battery last before it needs to be replaced?

      
Depending on several factors including usage and charging practices, a properly maintained MC-GPS system battery and GPS receiver battery, on average, last up to one year before needing replacement.
        

      

 Q4  How can I tell if my MC-GPS battery needs to be replaced?

      
If your MC-GPS unit's system battery needs to be charged after less than 8 hours of use, you probably need to replace your system battery. On average, the MC-GPS system battery should run for above 10 hours on a full charge. 

An indication that your GPS receiver battery needs to be replaced is if after charging overnight, the GPS receiver only works a short time before giving you the "LOW" message in the Tracking Status Indicator.
            

   

 Q5  What is the proper procedure for changing a GPS receiver battery in the field?

      
Follow the procedure below: 
  
 
Turn off the GPS receiver by pressing [ON] then [F2] 

  Turn off your MC-GPS unit

  Replace your GPS receiver battery 

  Perform a hard reset by using a ballpoint pen to gently depress the RST button located near the COM: ports.
         

  

 Q6  What is the appropriate care and maintenance of my MC-GPS battery?

      
Your MC-GPS unit comes equipped with two battery packs: a system battery pack to power the MC5 computer and a receiver battery pack to power the GPS receiver. The GPS receiver battery is located on the back of your MC-GPS unit. The system batteries and the GPS receiver battery have separate charging ports and charging circuits. To optimize your battery life, please follow the guidelines below. 

System Battery Maintenance

When fully running, your MC-GPS system battery will last for over 12 hours before it needs to be recharged. You may check the power level of your system battery as follows: 

Option #1:
Press [SH1], then [ENTER]. The System Status screen will be displayed. Press [F1](SYS) to view the current power level of the system battery; 

OR 

Option #2:
Press the [ON] key. The current power level for your system battery is displayed under Power (%). 

Use only CMT's ACC-RE3 (110V), ACC-RE3B (110V), ACC-RE4 (220V), or ACC-RE5 (cigarette lighter adapter) charger to recharge the system battery. You should recharge the system battery when one of the above indicators shows that system power is below 20%. The system battery must be recharged continuously for 16 hours. 

NEVER allow the battery to charge longer than 16 hours; doing so may result in permanent damage to your battery and/or your unit. 

If your MC-GPS is equipped with a 2100 mAH or higher-capacity system battery, you must use the ACC-SMC-G3-M "Smart Charger" to recharge your battery. The advantages of using one of the Smart Charger options include: 
  • A complete discharge of your system battery prior to recharge
  • Charging time of 10 hours or less, including discharge
  • The Smart Charger will apply a trickle charge to your battery after charging is complete to maintain the maximum charge


GPS Receiver Battery Maintenance


The GPS receiver battery lasts for 4-5 hours of continuous use before needing to be recharged. The tracking status indicator will display the word 'LOW' and the unit will issue a series of cascading beeps to notify you that the GPS battery needs to be recharged. Then, MC-GPS shuts off the GPS receiver automatically. 

For newer MC-GPS-IC units (for example MC5GPSDRD3-IC), you can check the power level of the GPS receiver battery as follows: 

Press [SH1], then [ENTER]. The System Status screen will be displayed. Press [F2](2ND) to display the battery level of the GPS receiver battery. 

Note: When you install a freshly charged GPS receiver battery in an -IC unit, you must manually update the GPS receiver battery level in this screen. 

To recharge the GPS receiver battery, you MUST use CMT's ACC-RE6 (110V), ACC-RE6B (110V), ACC-RE11 (220V) or ACC-RE5-G (cigarette lighter adapter) charger. 

The GPS receiver battery must be charged continuously for 16 hours. 

NEVER allow the battery to charge longer than 16 hours, since this may result in permanent damage to your battery and/or your unit. 

If your MC-GPS is equipped with a GPS-ENG-BAT-G3 GPS battery, you must use the ACC-SMC-G3-L "Smart Charger" to rechage your GPS battery. You may recharge this battery when it is inside or outside your MC-GPS. 

Do not try to use your GPS receiver while it is connected to the recharger. Instead, purchase an additional GPS receiver battery so that you can swap a fully charged battery into the MC-GPS.
         

  

 Q7  Can I use an external antenna with my MC-GPS?

      
Yes, an external antenna can be attached to a range pole or magnetic mount. For use with the MC-GPS. 

The built-in antenna may be detached from the MC-GPS. The bracket that attaches the antenna to the MC-GPS should remain connected so you can place the cable from the external antenna in the strain relief channel of the bracket, to remove stress from the connection to the antenna port.

         

  

 Q8  The Tracking Status Indicator always shows "STS", "IAC" or "INS". How can I make it go to "N3Dx" mode?

       
First, check your unit for the problems below: 

  Is the antenna connected? 
  Is the antenna unobstructed? 

Next, select "Setup" from the Main Menu and verify the following settings:

  Is a correct approximate position entered in the SETUP RECEIVER screen (i.e., longitude E or W, latitude N or S)? If necessary, make any changes and press [F4](SAVE) to send this information to the MC-GPS (the GPS receiver must be ON).

  Is a reasonable Elevation Mask specified in the SETUP RECEIVER screen? The default value is 5. This is the recommended setting. If necessary, make any changes and press [F4](SAVE) to send this information to the MC-GPS.

  Does your unit have the correct UTC time and date in the SETUP TIME/DATE screen? You need to set the correct Local time and date, and the correct UTC TIME OFFSET (for example: the UTC time offset for Pacific Standard Time is -8 hours). If necessary, make any changes and press [F4](SAVE) to send this information to the MC-GPS (the GPS receiver must be ON).

Then, confirm your GPS receiver has a current almanac. Follow the procedure below to check the almanac: 

Make certain that your GPS receiver is on, then, from the MAIN MENU, choose SETUP\RECEIVER. Scroll down with the Arrow keys to the ALM? prompt and change it to "YES". Then hit [F4](SAVE) to send the almanac to the receiver. 

Finally, your MC-GPS may need to be reset. Gently press the RST button (located near the COM: ports) with a ballpoint pen.

Double-check all of the above problem areas. If you are certain that your MC-GPS is set up correctly, but it still will not track satellites, please contact CMT for assistance. 
         

 


 Q9  Why does my MC-GPS stay in "TRK" mode even when I am tracking 4 or more satellites?

       
It is probably a settings issue. Check the following settings:
   
   From the Main Menu, select "Setup" and then choose "RS232 Input/Output". Then, from the RS232 setup screen, check the MODE setting for COM2. If it is set to "YES", change it to "AUTO". Press [F4](SAVE) to save the setting.

   Then, go to the Setup menu and choose Setup Receiver. From the Setup Receiver screen, check the ALT. CTRL field. If it is set to "3D ONLY", change it to "AUTO". 

Also check the DOP settings (PDOP, VDOP, HDOP). The default values are: PDOP>9, VDOP>8, HDOP>4. These are the recommended settings. Be sure to press [F4](SAVE) to save the settings.
                

   

 Q10  Why does my MC-GPS stay in "N2Dx" mode even when I am tracking 4 or more satellites?

       
There are two primary reasons why this might happen: 

Reason #1:
From the Main Menu, select "Setup" and then choose "Receiver". If you have set the ALT. CTRL field in the SETUP RECEIVER screen to MANUAL, the MC-GPS will always display the input altitude for your position. Therefore, the MC-GPS does not generate an altitude based upon the GPS data it is collecting and always displays a status of N2Dx or F2Dx. Change the ALT. CTRL. setting to AUTO or 3D ONLY and press [F4](SAVE) to save the settings.

Reason #2:
 If the VDOP level set in the SETUP RECEIVER screen is exceeded and the ALT. CTRL field is set to AUTO, the MC-GPS will generate and log 2D data. 
         

 

 Q11  I have an RTCM device (e.g., Coast Guard Beacon) attached to my MC-GPS, but the Tracking Status indicator never goes into "N3Cx" mode. Why?

       
There are three primary reasons why this might happen:

  The beacon receiver itself is not receiving corrections. Confirm that the "Lock" indicator displays a green light on the beacon receiver. If it does not, the beacon receiver may be out of reception range or have low battery power. Confirm that a fully charged battery is connected to the beacon receiver.

  The beacon receiver is attached to the wrong COM port on your MC-GPS. It should be attached to COM2.

  The RTCM settings on your MC-GPS are incorrect. Go to the Setup menu and select RS-232 Input/Output. The settings for COM2 should be as follows:
           BAUD> 4800 MODE> AUTO
           AGE LMT: 15 (SEC)
Confirm these settings and press [F4](SAVE).
         

 

 Q12  How can I collect a point feature (like a sign) in the midst of collecting a line (like a road) or an area (like a tract)?

       
Use the nested point feature. While storing a line or area, press [F2](PNT) in the Featuring Screen. Then, name the nested point, attach attributes and values, and press [F4](STORE). After you store the nested point a message comes up asking whether you want to continue storing the line or area or store another nested point.
         

 

 Q13  How do I set up my MC-GPS as a Base Station?

       
Immediately after selecting "Collect Data" from the Main Menu, press F3 [BASE] in the Job Data screen . The Base Logging Mode allows 2 options, Base and BasePC. 

The Base mode will store the differential correction file in the I: drive of the MC-GPS. After selecting Base mode, a screen appears showing the memory remaining. When you press [F1](START) the Start Time appears. [F1](STOP) stops the logging of base data. 

BasePC mode uses Kermit as a transfer protocol to store the base file onto a PC. Connect to your PC just as you would for standard file transfers.
         

 

 Q14  How can I get real-time differential correction in the field with my MC-GPS?

       
There are three main sources of real-time correction data: 

1. Coast Guard Beacons (DGPS) (See CMT's Beacon Receiver Package.) 
2. Subscription Service 
3. Broadcast from your own base station
         

 

 Q15  How far can I be from a Base Station and still get accurate differential corrections?

       
For 1 - 5 m accuracy, you must be within 300 miles of a base station. 
         

 

 Q16  How can I optimize my data collection when I am in a city's downtown area or in a canyon?

       
Make certain that SEL CONSTELLATION in the SETUP RECEIVER screen is in CANYON mode, so the 6 channel receiver will search for the 6 highest satellites in the sky. CANYON mode is the default. 

Choose the best time of day to be in the field using PC-GPS's mission planning function. The most effective method of determining satellite availability is to view the DOPs chart. You may also simulate terrain features and other obstructions by setting MASKS in OPTIONS\MASKS. 

In certain situations you may only be able to collect 2D data. If you know the elevation at which the data was collected, you can differentially correct the data by setting ALT. CONTROL in GPS\DIFFERENTIAL\CA CODE\SETUP to "Altitude Always Fixed" and inputing the correct altitude. All nodes in the Job will be fixed to that altitude, and you will then be able to differentially correct otherwise uncorrectable 2D data. 

Note: Be careful when using the "Altitude Always Fixed" option: one third of any error in the altitude will add to horizontal error. For instance, if you fix the altitude of a point to 30 meters HAE and the point was really at 60 meters HAE, you have just added 10 meters (30/3) of error to the horizontal position. 
         

 

 Q17  Does rain affect data collection?

       
According to the US Department of Defense, GPS is an "all weather" technology. However, in cases where there is heavy canopy and snow or rain, GPS signals may be disrupted. The MC-GPS itself is completely waterproof and will not be affected by rain, mud, etc., as long as the air valve is closed.
         

 

 Q18  Why does my MC-GPS go in an out of Navigating or Featuring mode when I am collecting data?

       
The GPS signals may be blocked by obstructions (i.e., buildings, trees, etc.) causing the MC-GPS to lose track of satellites. 

Also, be aware of how you hold the MC-GPS; make certain that the antenna is not blocked by your body. If you are consistently having this problem, then you may want to consider an external antenna.
         

 

 Q19  How accurate is the MC-GPS at locating one's position?

       
With differential correction, the horizontal accuracy is from 1-5 meters (95% of the time) when HDOP < 4. Without differential correction, 95% of the time your position is within 38 meters when HDOP < 4 (with SA off). 

Differential accuracy can be described as 2 meter CEP accuracy (CEP, for Circular Error Probability, means 50% of points will be within 2 meters of your true location) or as 2.5 meter RMS accuracy (RMS, for Root Mean Square, means that 63% of points will be within 2.5 meters of the true location), or as 5 meter 95% confidence accuracy (95% of points will be within 5 meters).
         

 

 Q20  How do I reset my MC-GPS?

       
Under normal conditions, you do not need to reset the MC-GPS. However, you should know how to reset the machine in case there is a need to do so.

There are two ways to reset and reboot the MC-GPS:

1. Hold down the [F3] key and then press the [ON] key. This is the equivalent of a [CTRL][ALT][DEL] sequence on a PC. The MC-GPS will reboot itself.

2. Use the tip of a ball-point pen to press the RST button located near the COM: ports. The MC-GPS will turn itself off. Press [ON] to restart the CMT Field program. After some screen activities, you will see the MAIN MENU displayed.

Warning: Do not reset the MC-GPS while you are collecting data in the CMT Field program. Doing so may irreversibly corrupt the associated data files. In case you get stuck in a program or in the MC-GPS operating system, try holding the [F2] key down and pressing [ON]. Normally, this will terminate any running program and turn off the MC-GPS. When you press the [ON] key again, the program will be restarted without any adverse effect on the data files.
         

 

 Q21  Why did my MC-GPS hang up when I tried to open or create a Job?

       
Your I: drive may be full. Free up additional disk space by deleting old data files (after archiving them on your PC or a floppy disk).
         

 

 Q22  Does my MC-GPS need any maintenance if I don't plan to use it for a month or more?

       
Yes. Your MC-GPS batteries requires recharging every month, even if the MC-GPS is not being used. Failure to follow a regular recharging schedule is one of the major causes of data and formatting loss, and can permanently damage your batteries. 

Click here for complete instructions on the care of your batteries during long-term storage.
   

 

 Q23  I received a "Can't write file" error in the middle of my GPS Job. What should I do?

       
This message may indicate that the MC-GPS's RAM disk is full. 

First, press [ON] to go to the Status screen and check the available memory. It is likely that you will need to delete some old GPS jobs to free up disk space.
         

 

 Q24  After using my MC-GPS for a while under the sun, the display becomes too dark to read. What should I do?

       
Press [SH1] and then [ENTER] to call up the System Status screen. Then press the [F3](CONT) key to display the Contrast screen. Now press the minus (-) key several times to lighten the display. Later, when you go into the office or a cooler area, you may use the plus (+) key in the Contrast screen to increase the display contrast.
         

 

 Q25  I received a "Not enough memory. Part of it plotted" error when I tried to plot a Job. What should I do?

       
This is caused by memory fragmentation. You can solve this problem by resetting the unit. Then the unit will be able to display the plot for a larger Job.  If this problem persists, the Job you are trying to plot may contain too much data to be plotted completely.
         

 

 Q26  I received a "DISK FULL" message in the Featuring screen while storing a Feature. What should I do?

       
Quit the current Job and transfer the collected Jobs to PC-GPS. After you have transferred the Jobs to PC-GPS you delete the Jobs from the MC-GPS.
         

 

 Q27  After I reset the MC-GPS, I get a "Low Power" message. What should I do?

       
When this message is displayed, the MC-GPS does not have sufficient power to run the CMT Field program. You will need to charge or replace the system battery. After you have charged or replaced the system battery , you will also need to reset the MC-GPS by pressing the RST key or using the F3-ON key sequence. 

If you do not reset the unit, the CMT Field application will act as though it is a basic unit without any options (such as NMEA, RTCM, PHASE). This means that the VERSION screen will not display a line that says: "OPTION: RTCM + NMEA". Also, in the "DEVICE" field in the INPUT/OUTPUT setup screen, the only option available will be "BARCODE". 

In other words, the options list is determined when the software is started. You cannot change it by charging the system battery or installing a new battery pack. You must reset the option list by resetting the MC-GPS in order to access the options provided with your MC-GPS unit.
         

 

 Q28  What are the signs that my MC-GPS needs to be reformatted?

       
If you perform a soft reset (i.e., hold down [F3] and press [ON]) and the MC-GPS goes to the F: drive instead of starting the CMT Field program, you need to reformat your unit. 

This problem is likely to arise in the following situations: 

* The MC-GPS was allowed to sit for over a month without a system battery recharge. 
* The system battery was replaced incorrectly. 
* The system battery was low, but the MC-GPS was allowed to sit for a few days without being recharged. 
         

 

 Q29  What is the drive configuration of the MC-GPS?

       
The configuration of the unit is as follows:
  
DRIVE: SIZE OB or OPEN USUAL FORMAT 
A:  128K  OB  MEMORY
B:  128K  OB  MEMORY
C:  128K  OB  FILES 
D:  128K  OB  FILES (JOINED WITH C: )*
E:  128K  OB  FILES - MC-GPS Programs
F:  ROS  OB  OS (ROS)
I:  RAM  OB  RAM DISK
J:  MC-GPS Program  OB  APPLICATION (GPS PROGRAMS)


* A & B drives must be memory drives and C & D must be joined as FILE system
**  ASIC
1MB, 2MB, 3MB, 5MB, 8MB  RAM disk  (3 slots ROS, GPS, and other)
Non-ASIC  
 1MB, 2MB, 4MB, 8MB  RAM disk  (2 slots ROS and GPS)
*** Other possible drives:       ASIC  K: - U:
                                    
non-ASIC  K: - Q:
           

 

 

 Q30  How do I format my MC-GPS?

       
In the case that a MC-GPS unit goes down, it should re-format itself after it has started back up. If it doesn't, you need to go to the Operating System and type:

"FORMAT C: 256" and press enter. Then answer "Y" and press enter.

NOTE: If you get an "ERROR: Format Device Error", you must follow the steps to break out into the OS from the splash screen below, and then re-issue the FORMAT C: 256 command from a drive other than C:
         

 

 Q31  How do I format the RAM Disk?

       
The RAM disk is installed in Drive I. To format this drive, follow these steps:

  Break out into the Operating System by pressing Esc, then make sure that the file, 'EDISK.X' is in the C: drive. If it is not, copy it there from either the J: or K: drive.

  From the MC-GPS Operating System, type: EDISK -d and press enter.

  Hit enter one more time in the next screen. The RAM disk is installed.

  Type: FORMAT I: and press enter. Then answer "Y" and press enter.
         

 

 Q32  How do I "break out" into the OS from the splash screen?

       
How do I "break out" into the OS from the splash screen?

If you are unable to get to the operating system (i.e., the MC-GPS is stuck in the splash screen ...."Please Wait....." ), use the following commands to break out:

  Hold down [F3] and hit [ON] to reset the MC-GPS.

  While the autoexec file is running, hold down [F1] and hit [ON] to stop RS232 and EDISK from installing.

  You may need to repeat the steps above a few times to get the timing correct. You need to time the [F1] [ON] sequence just right to stop RS232 and EDISK from installing.