Using GMapTool to combine multiple maps into one mapset file for Garmin GPS

We mentioned earlier that Garmin GPS navigator supports several mapset files. That should be enough for normal users.

Saving different map into different mapset file also makes it easy to replace the map to newer version in the future, as well as convenient to remove a single map from the GPS storage.

However, if you have a lot of map that you want to load into your GPS, or you want to store all the maps into SD card which supports only a single gmapsupp.img in it, you might need to combine (join) the maps into one mapset file by using specific software tool. GMapTool is one of the powerful tool which allow you to join and/or split maps in mapset file.

You can visit this webpage to download GMapTool. It supports multiple platform:

• Windows - GUI and command line
• Linux - command line
• Mac OS X - command line
  
  
  

By using the GUI interface of GMapTool, it is pretty simple to combine the mapsets.

Firstly, store all the mapset files you wish to combine in different filename in your PC. It is recommended to store them in the same folder/directory.

Under the Files section of GMapTool, select the maps you want to combine by clicking on Add Files (to select one file at one time) or Add Directories (to select all *.img files in the directory). Note that you can always remove any file in the listing by selecting it and press the Delete button of your keyboard.

When you are done with the mapset selection, continue to the Join section.

Specify the Output File, and key-in the Mapset name of your file to be created. This mapset name will be displayed under each of the map name when you list your maps in Map Info function of your Garmin GPS.

Click the Join all button, and the combined mapset will be created. You can then copy the new mapset file to your Garmin's internal storage or SD card.

Note that if any of the maps in your mapset file is locked by vendor, you still need the 25 bytes unlock key stored in a *.unl file in the same folder and with the same name as the mapset file where the locked map is stored in. To unlock 2 maps inside the mapset file, put both the keys inside the *.unl file one after another, without space (the file size will be 50 bytes then).

To get rid of the hassle, you might want to use another tool called Garmin Unlocker to permanently unlock the maps before combining them with GMapTool.

You might probably be interested to also read about:

• Using GMapTool with cGPSmapper to convert finalized gmapsupp.img back to MapSource maps
• Fixed GMapTool problem regarding "Multiple products in img, creating TDB aborted"

Inside of the Garmin Nuvi 255w GPS exposed

No, I have not opened up my Garmin Nuvi 255w GPS to see what is inside, but others did.

You can click here to go and see some interesting photos of the internal electronic parts of the Nuvi 255w device after the cover is opened up.

And here is a professional technical write-up on the internal of Garmin Nuvi 205, which is a smaller and more compact unit with 320x240 display in the Garmin 2x5 family.

Click here to see the interesting photos of the internal of Garmin Nuvi 205 (with label description).

From these information, we can guess that our Garmin Nuvi 255w GPS is having:

• STMicro Cartesio (STA2062) processor
  
• Rx Networks GPStream SAGPS chipset
• STMicro STA5620 single-chip RF front end
• 32MB DDR SDRAM
• 2GB Sandisk iNAND internal flash memory
• Rechargeable 3.7-v/1250 mAh Li-Ion battery
• Sharp-manufactured LCD touchscreen

Garmin Hotfix technology powered by Rx Networks GPStream SAGPS chipset

Newer Garmin Nuvi GPS including the 205, 205w, 255, 255w, 265T, 265WT, 275T, 500, 550, 750, 760, 770, 780, 755t, 765t, 775t, 785t, 850, 880, 5000, etc. have a new selling point of Hotfix technology.

Garmin Hotfix enable the GPS to be super fast within seconds in locating the satellites during startup. In fact, my Garmin Nuvi 255w can even work as if staying connected to satellites for a few minutes, when it started up indoor in the middle of my house.

This is made possible by using predictive calculations of satellite positions, which enables the behaviour of GPS satellites to be modelled based on broadcast ephemeris readings for accurate prediction of satellite positions up to a few days ahead. A single broadcast ephemeris reading allows the accurate prediction of satellite orbits which are developed and refined every time new broadcast ephemeris is obtained.

Some people are guessing that the Hotfix feature is based on SiRF InstantFix inside the newer version of SiRFstarIII chipset. However, we've just found out that Nuvi 255w is using STMicro Cartesio application processor instead, so it is not SiRF InstantFix which plays the magic.

In fact, the Garmin Hotfix technology is powered by Rx Networks GPStream SAGPS chipset. The GPStream Self Assisted GPS (SAGPS) is a derivative of GPStream Predicted GPS (PGPS) technology. GPStream PGPS is a 3rd generation Assisted GPS (AGPS) solution addressing the limitations of 1st and 2nd generation products, which is made available to some handphone devices with AGPS feature.

Click here to read more about Rx Networks GPStream SAGPS technology.

For those who are interested to know where I got the information about Garmin Nuvi 255w is using STMicro Cartesio application processor and Rx Networks GPStream SAGPS technology, it is mentioned in Page 10 of September 2008 edition (Volume 11 Issue 9) of Telecom Trends newsletter.