1. How do I test my communication port?
2. My GPS has a serial cable interface, but my computer only has USB ports.
3. The coordinates in GPS Utility differ from GPS values.
   What are Datums?
4. How does GPS Utility deal with altitude information?
5. Sometimes there is a difference of 1 in the last digit of a coordinate
6. I am having printer problems.
7. Why do the eTrex (and eMap) tracks show a timestamp of 31-DEC-1989
8. Why do I not get the trackpoint creation time when I download tracks from my Magellan 315/320?
9. How can I upload maps to my Garmin receiver?
10. Can I use GPS Utility to delete waypoints in my GPS?
11. What is Selective Availability?
12. I cannot import the 'intermediate' waypoints from AutoRoute Express / Streets and Trips

How do I test my communication port?

Do the following steps:

1. Check that you have the correct port number set up in GPS|Setup...
2. If you get a message saying 'Could not Connect ...' check that no other program is using the communication port. Check your Start up folder to see which other programs may be active and could have grabbed the port.
3. Set the Interface mode to NMEA and click OK.
4. Start the Interface Monitor from the GPS menu.
5. Do GPS|Connect and you should see "CONNECTED to NMEA interface".
6. Now set your GPS unit to transmit NMEA (if Magellan, then also make sure that it has a satellite view, is locked on and producing a position). You should now see incoming NMEA messages in the Interface Monitor. This tests that the basic connect and download wire are functioning correctly.
7. If you suspect that the upload wire is not working, then create a TEST waypoint in a New window. Remove the GPS unit from the cable and then connect a short piece of wire between the Data-Out and Data-In pins (check your manual for the pins). This will loop any outgoing signal back as an incoming signal. Do GPS|Upload Waypoints and you should see the upgoing waypoint returned e.g:

   ->$GPWPL,0000.000,N,00000.000,E,TEST*5D
   Finished with Comms.
   <-$GPWPL,0000.000,N,00000.000,E,TEST*5D
   

   If this is successful then the cable and communications port would appear to be working. Remove the wire link and reconnect your GPS to the cable.
8. Do GPS|Disconnect and select the correct interface mode for your GPS receiver (Garmin or Magellan). Set your GPS receiver to the correct transfer mode (e.g. GARMIN or GRMN/GRMN). Do GPS|About and you should a small panel with see some information relating to your GPS model.
9. If you have been successful with the 'loop' test above, but still cannot get your GPS to work in Garmin or Magellan mode, then jiggle the connector at the GPS receiver end. The eTrex/eMap are particularly prone to having poor contacts between the cable and the receiver.
10. If you suspect GPS Utility does not fully support your GPS then please send a note to the author containing the information given by GPS|About. It would also help if you saved the connect sequence interface trace by doing SaveAs... in the Interface Monitor and attaching the trace file to the email.

My GPS has a serial cable interface, but my computer only has USB ports.

To connect a GPS with a serial cable to a computer which only has USB ports you need to obtain a USB/Serial cable adapter, such as the "USB-Serial Cable Adapter" available from www.pfranc.com.

The cable comes with a software driver which you must install first. When you plug the cable into a USB socket on your computer, the software creates a virtual serial port within the computer to which GPSU can connect. Connect you GPS via its own serial cable to the adapter cable.

In Windows XP, go to the Control Panel -> Performance and Maintenance -> System ->Hardware -> Device Manger -> Ports to see which virtual serial port your software has generated. Use this port number in GPSU|Setup...

It is possible that the port number may change on different bootups so you may need to check this.

The coordinates in GPS Utility differ from GPS values.
    or:
What are datums?

This is usually because you have set different datums in GPS Utility and in your GPS receiver. Coordinate values are referenced to a particular datum and so when you change datums the coordinate values will change. The actual position does not change, it is just the distance from the "origin" that has changed. When you change datums you change the origin of the coordinate system that you are using.

Check which datum you have set in the GPS and which datum you have set in GPSU.

For more details, see Datums.

How does GPS Utility deal with altitude information?

Altitude can be referenced to any of:

1. The WGS84 ellipsoid (a mathematically defined surface which forms the basis for GPS position calculations)
2. A selected datum's ellipsoid (another mathematically defined surface - shifted with respect to the WGS84 ellipsoid, but usually defined to closely match the local surface of the Geoid for a geographic region).
3. A Geoid (a surface of equal gravitational potential - caused by density variations within the earths crust)
4. Mean Sea Level (slightly different from the Geoid surface, because of permanent ocean currents, winds, temperature and salinity differences)

Data transmitted using the Garmin protocol is transmitted in WGS84 and GPS Utility assumes that the altitude is referenced to the WGS84 ellipsoid. If there is no altitude data in the message, then the value is taken to be zero. If you now display this data using some other datum, the altitude is referenced to that datum and you will see a value which represents the difference in height between the two datums (or ellipsoid surfaces).

Data tranmitted using the NMEA interface, is referenced to a user selected datum. GPS Utility ASSUMES that you have set the same datum as the GPS unit and displays the altitude as received over the interface without change.

GPS Utility therefore displays the altitude as an 'ellipsoid' height. It does not have a 'geoid' height model which would account for local variations of the gravitational field. Mean Sea Level may differ from the the ellipsoid surface by a number of metres. Over a local area, this offset will be fairly constant.

You may like to read about the seven level headed scientists who can explain this much better.

Sometimes there is a difference of 1 in the last digit of a coordinate

If the internal form is then transmitted to GPS Utility, this may be quantised for transmission over the interface. When GPS Utility receives the quantised coordinate, it then performs the datum and grid transformations and then rounds the value for display. This rounding can result in a value that differs by +/-1 in the final digit from the value shown in the GPS.

I am having printer problems

In the case of Epson printers, you need to go to the Epson web site.

Don't assume that you have the latest driver as the Epson site only lists V5.0 (dated Dec'99) but if you download this you will find the setup program refers to it as V5.24 (or later). So install this as per the instructions and hopefully this will fix the problem.

Why do the eTrex (and eMap) tracks show a timestamp of 31-DEC-1989

The eTrex records a timestamp for each trackpoint in the Active Log. However, when this is saved as a Stored Log, the timestamp is "stripped from a saved tracklog to reduce the amount of memory taken up" (according to Garmin). If you download a Stored Log, then the date is given as 31-DEC-1989 (GPS time zero). If you upload a track as an active log, then the timestamp is also set to the default value. Only an eTrex derived active track log contains valid time value.

Why do I not get the trackpoint creation time when I download tracks from my Magellan 315/320?

The original software as shipped with the Magellan 315/320 does not provide the trackpoint creation date and time in track download. GPSU defaults to the time at which the trackpoints were downloaded. Software version 3.12 (or later) obtainable from the Magellan website should fix this problem. You need to upgrade your 315/320 to the latest software version.

How can I upload maps to my Garmin receiver?

It is not possible to upload scanned image maps to a Garmin receiver.

Garmin software can upload vector maps (i.e. those consisting of drawn lines). However, Garmin have not published the interface protocol for uploading vector maps and so this function is not supported in GPS Utility.

The best you can do with GPS Utility is to create tracks which can be used as 'pseudo maps'. You can do this by digitising tracks using scanned maps - see the Help topics 'mapping' and 'digitising'. The maps are a bit crude, but it does work for some purposes.

Can I use GPS Utility to delete waypoints in my GPS?

Sorry, it is not possible to delete individual waypoints in your GPS from a PC. The workaround is to download all the waypoints, delete those you do not need, clear all waypoints in your GPS receiver and then upload those that you want to keep.

What is Selective Availability?

As of midnight on the 1st May 2000, SA was discontinued under orders of the President Clinton. Selective Availability was the purposeful degradation of the GPS signal for civilian users. This took the form of a timing 'jitter' in the signals coming from the satellites giving a slightly erroneous position (up to 100m for 95% of the time). The military could decode the signal correctly and remove the jitter. Without SA the error is about 15m horizontally and 25m vertically for 95% of the time.

I cannot import the 'intermediate' waypoints from AutoRoute Express / Streets and Trips.

The intermediate waypoints displayed in AutoRoute Express or Streets and Trips are NOT exported in the file - they are obtained when needed from the CD data base which is encrypted. Therefore they cannot be imported into GPS Utility.

If you want intermediate route waypoints, then you need to define them as 'Stop' or 'Via' points first. These are exported and can be read by GPS Utility into a route.

If you also capture the AutoRoute Express/Streets and Trips screen image, then you can calibrate this map image using your Start and End points and then you can quickly digitise the route as a track ready for upload to your GPS receiver. More information regarding this technique is available in Hints and Tips.

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