HP-GPS-L4
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

 

HP-GPS-L4 Frequently Asked Questions

General Information
Q1 How long can I collect data with a 4 MB RAM Disk?
Q2 How long should my HP-GPS-L4 batteries last in the field before they need to be recharged?
Q3 How long should my HP-GPS-L4 batteries last before they needs to be replaced?
Q4 How can I tell if my HP-GPS-L4 batteries needs to be replaced?
Q5 What is the proper procedure for changing a GPS engine battery in the field?
Q6 What is the appropriate care and maintenance of my HP-GPS-L4 batteries?
Q7 Can I use an external antenna with my HP-GPS-L4?

Satellite Tracking
Q8 The Tracking Status Indicator always shows "IAC" or "INS". How can I make it go to "N3Dx" mode?
Q9 Why does my HP-GPS-L4 stay in "TRK" mode even when I am tracking 4 or more satellites?
Q10 Why does my HP-GPS-L4 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 HP-GPS-L4, 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 HP-GPS-L4 as a Base Station?
Q14 How can I get real-time differential correction in the field with my HP-GPS-L4?
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 HP-GPS-L4 go in an out of Navigating or Featuring mode when I am collecting data?

Q19 How accurate is the HP-GPS-L4 at locating one's position?

Hardware Issues
Q20
How do I reset my PC5L?
Q21 Why did my PC5L hang up when I tried to open or create a Job?
Q22 Does my HP-GPS-L4 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 HP-GPS-L4 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 HP-GPS-L4, I get a "Low Power" message. What should I do?

Formatting Issues
Q28 What is the drive configuration of the PC5L for the HP-GPS-L4?
Q29 How do I format the RAM Disk?

 

  Q1  How long can I collect data with a 4 MB RAM Disk?

       
4 MB will store more than 32,000 point features, which is often enough for a day of work. You can fill a 4 MB RAM Disk with GPS data in about 10 hours when you continuously log a line or area feature. Each HP-GPS-L4 unit comes with a PC5L data collector containing 4 MB of RAM for data storage, plus an additional 1.5 MB of RAM for storing applications or other files.

If your application will involve collecting line or area features for long periods of time you may want to consider 8 MB of RAM for data storage.

 

 Q2  How long should my HP-GPS-L4 batteries last in the field before they need to be recharged?

      
The PC5L data collector batteries (system battery) should last about 10 hours before recharging is necessary. The field-replaceable GPS engine batteries should each give 4-5 hours of continuous use (or over 10 hours of continuous use when used in parallel) before requiring recharging.

   

 Q3  How long should my HP-GPS-L4 batteries last before they need to be replaced?

      
Depending on several factors including usage and charging practices, properly maintained HP-GPS-L4 batteries, on average, last up to one year before needing replacement.

      

 Q4  How can I tell if my HP-GPS-L4 batteries need to be replaced?

If your PC5L batteries needs to be charged after less than 8 hours of use, you probably need to replace your battery.  On average, the PC5L should run for about 10 hours on a full charge .

An indication that your GPS receiver batteries need 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 engine battery in the field?

      
Follow the procedure below: 
  
 
Turn off the GPS receiver using the toggle switch.

  Disconnect the power cable from one or both batteries.

  Replace one or both batteries and re-connect the power cable.         

  

  Q6  What is the appropriate care and maintenance of my HP-GPS-L4 batteries?

  
Your HP-GPS-L4 unit comes equipped with two battery packs: a system battery pack to power the PC5L computer and one or more receiver battery packs to power the GPS receiver. The GPS receiver batteries are housed in the backpack of your HP-GPS-L4. The PC5L battery and the GPS receiver batteries have separate charging ports and charging circuits. To optimize your battery life, please follow the guidelines below. 

PC5L Battery Maintenance

When fully running, your PC5L battery will last for over 10 hours before it needs to be recharged. You may check the power level of your system battery as follows: 

1. Press [SH1], then [ENTER]. The System Status screen will be displayed. Press the DOWN ARROW key once to select Powermeter. Press enter to see the current power level of the system battery; 

OR 

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 PC5L is equipped with a 2100 mAH or higher-capacity system battery, you must use the ACC-SMC or ACC-SMC-G2-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

Each GPS receiver battery lasts for 4-5 hours of continuous use (or for 10+ hours of continuous use when used in parallel) 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, HP-GPS-L4 shuts off the GPS receiver automatically. 

There is no power level indicator for the GPS receiver batteries. 

To recharge the GPS receiver battery, you MUST use CMT's ACC-SMC-G2-P "Smart Charger".

  

 Q7  Can I use an external antenna with my HP-GPS-L4?

      
Yes, an external antenna can be attached to a range pole or magnetic mount. For use with the HP-GPS-L4. 

The built-in antenna may be detached from the HP-GPS-L4. The bracket that attaches the antenna to the HP-GPS-L4 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 "IAC" or "STS". 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 HP-GPS-L4 (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 HP-GPS-L4.

 
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 HP-GPS-L4 (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 SEND ALMANAC? prompt and change it to "YES". Then hit [F4](SAVE) to send the almanac to the receiver.  

Finally, your PC5L 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 HP-GPS-L4 is set up correctly, but it still will not track satellites, please contact CMT for assistance. 


 Q9  Why does my HP-GPS-L4 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. CONTROL field. If it is set to "3D ONLY", change it to "AUTO". 

Also check the DOP settings (PDOP, VDOP, HDOP). The defaultvalues 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 HP-GPS-L4 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. CONTROL field in the SETUP RECEIVER screen to MANUAL, the HP-GPS-L4 will always display the input altitude for your position. Therefore, the HP-GPS-L4 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. CONTROL. 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. CONTROL field is set to AUTO, the HP-GPS-L4 will generate and log 2D data.          

 Q11  I have an RTCM device (e.g., Coast Guard Beacon) attached to my HP-GPS-L4, 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 not attached to the GPS receiver. Check all physical connects inside the HP-GPS-L4 backpack.

  The RTCM settings on your PC5L 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 HP-GPS-L4 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 HP-GPS-L4. 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 HP-GPS-L4?

       
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 sub-meter 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?

       
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 PC5L itself is completely waterproof and will not be affected by rain, mud, etc., as long as the air valve is closed. Other components of the HP-GPS-L4 (e.g., cables, GPS receiver batteries,) are also waterproof, but should be kept inside the protective backpack at all times during wet weather conditions.

 Q18  Why does my HP-GPS-L4 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 HP-GPS-L4 to lose track of satellites.

Also, be aware of how you hold the HP-GPS-L4; 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 HP-GPS-L4 at locating one's position?

       
With differential correction, the horizontal accuracy is around 30 centimeters (RMS) 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 40 centimeter CEP accuracy (CEP, for Circular Error Probability, means 50% of points will be within 40 centimeters of your true location) or as 90 centimeter 95% confidence accuracy (95% of points will be within 90 centimeters).

 Q20  How do I reset my HP-GPS-L4?

       
Under normal conditions, you do not need to reset the PC5L. 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 PC5L:

1. Hold down the [ON] key and then press the [F3] key. This is the equivalent of a [CTRL][ALT][DEL] sequence on a PC. The PC5L will reboot itself.

2. Use the tip of a ball-point pen to press the RST button located near the COM: ports. The HP-GPS-L4 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 HP-GPS-L4 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 HP-GPS-L4 operating system, try holding the [ON] key down and pressing [F2]. Normally, this will terminate any running program and turn off the HP-GPS-L4. When you press the [ON] key again, the program will be restarted without any adverse effect on the data files.

 Q21  Why did my HP-GPS-L4 hang up when I tried to open or create a Job?

       
Your RAM Disk, or 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 HP-GPS-L4 need any maintenance if I don't plan to use it for a month or more?

       
Yes. Your HP-GPS-L4 batteries requires recharging every month, even if the HP-GPS-L4 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 PC5L'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 HP-GPS-L4 for a while under the sun, the display becomes too dark to read. What should I do?

       
Press [SH1] and then [ENTER] on the PC5L to call up the System Status screen. Then press the DOWN ARROW key twice to select the Contrast option and press Enter. Now press the DOWN ARROW key several times to lighten the display. Later, when you go into the office or a cooler area, you may use the UP ARROW 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 PC5L.
         

 Q27  After I reset the HP-GPS-L4, I get a "Low Power" message. What should I do?

       
When this message is displayed, the PC5L 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 PC5L by pressing the RST key or using the ON-F3 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 PC5L in order to access the options provided with your HP-GPS-L4 unit.
         

 Q28  What is the drive configuration of the PC5L for the HP-GPS-L4?

          
The
PC5L has 1 MB of RAM in the D: drive. Of this 1 MB, 640k must be designated for system memory. The remaining RAM may be used for data storage. PC5L comes formatted like this from the factory. If you want to run an application program on HP-GPS-L4, put the program in the D: drive.
The C: drive is a Flash EEPROM which holds the
PC5L operating system.
The A: drive is a Flash EEPROM which holds the CMT-FIELD application software.
The B: drive is a 4 MB/8 MB PCMCIA RAM Disk for data storage.

A: Flash EEPROM
B: 4 MB/8 MB RAM Disk
C: OS
D: FILES

           

  

 Q29  How do I format the RAM Disk?

       
Exit to DOS (ESC from the Main Menu) and follow the instructions below:

  Go to the C: prompt.
  Type Format B:
  Answer yes to the prompt. 
  Type Format D:
  Answer yes to the prompt.

Both your drives should now be formatted.