Adding multiple maps in Garmin Nuvi 255w GPS

Theoretically, the Garmin Nuvi GPS navigator can be loaded with hundreds of map. The limit is on the maximum file size (about 2GB per file) and available storage memory.

The maps are stored in specific mapset files with *.img extension in the flash memory of the GPS unit. Each mapset file contains one or many maps in it. Beside that, the Garmin GPS navigator can also recognise and load up one additional mapset file from SD card residing in the "Garmin" folder and named as "gmapsupp.img".

Here are the mapset files supported by Garmin Nuvi 255w GPS navigator:

• gmapbmap.img - the default base map
• gmapprom.img - the primary mapset
• gmapprom1.img - the secondary mapset
• gmapoem.img - the OEM mapset that cannot be unselect by user (if it exist)
• gmapsupp.img - the supplemental mapset which you can have one in the GPS flash memory and another one in the attached SD card.

Therefore, the Garmin Nuvi 255w GPS supports up to 6 mapset files, including 1 in SD card. Normally new maps installed by the user will be stored in gmapsupp.img.

You will lost all the maps in the previous mapset file if it is overwritten by a new file with same filename. If you want to keep the existing maps, ensure that you store the mapset file with an unused filename (from the 5 filenames above). Alternatively, you can make use of special tools to merge new maps into existing mapset file.

You can view the name of your base map in Tools > Settings > System > About > Basemap.

You can view the name of maps in the other mapset files in Tools > Settings > Map > Map Info. There, you can tell the GPS to load the map by checking on its name, or not to use the map by unchecking it.

In case there are 2 or more non-overlaping maps available for the same location, the map with the highest priority number (defined in the map itself) will be used by the GPS.

Note that certain map which are locked by vendor need a 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.

You might probably also interested to read:

• Using GMapTool to combine multiple maps into one mapset file for Garmin GPS
• Using GMapTool with cGPSmapper to convert finalized gmapsupp.img back to MapSource maps

Accessing the built-in Diagnostic Utility in Garmin Nuvi 255w GPS

Just discovered that there is a "hidden" built-in Diagnostic Utility in Garmin Nuvi 255w GPS navigator.

You can access it by tapping on the battery icon on the upper right corner of the screen and hold for more than 5 seconds until the Diagnostic Utility come up. Here is how it looks like:

This built-in Diagnostic Utility allows you to see detail technical information of the GPS navigator and the attached SD card (if any). You can also use it to perform some test on its memory, voice, display, and other functions.

My Garmin Nuvi 255W GPS navigator

I have just bought a Garmin Nuvi 255W portable GPS navigator in PIKOM PC Fair II 2009 at the price of RM849. It is a SING/MAL unit which comes with new features such as Junction View, Lane Assist, etc.

Here are some useful information for those who are also interested in this model of Garmin GPS navigator. Note that this unit is a localized version sold in Malaysia and Singapore only.

In the packaging box, there is:

• The Garmin Nuvi 255W GPS navigator
• Vehicle suction cup mount
• Vehicle power cable
• Dashboard disk
• Quick start manual

Free gifts from vendor as PC Fair promotion:

• Screen protector film
• Garmin leather case
• USB cable

There is no complete user manual come with the box, but the full user manual in PDF format can be downloaded from Garmin website.

The following maps are preloaded in the GPS navigator:

• City Navigator Singapore/Malaysia NT v4.02
• Malsingmaps Malaysia/Singapore/Brunei NT 2009.5
• Thailand v9.0 EN (No Pain)

And I managed to install Malfreemaps v1.68 together with MFM SRTM Topo v1.02 available in http://www.malfreemaps.com/.

How do we know this is a SING/MAL unit which supports Junction View and Lane Assist?

• Underneath the packaging box, the SKU number should be 010-00718-69 and barcode labeled with "nuvi 255W, SING/MAL".
• In Tools > Settings > System > About screen, you should be able to see "SgMy Software Ver. 2.70".
• You can set the unit into simulation mode and travel through some major junctions around KL urban area to see how it works. Ask the vendor to demo to you on the unit that you're going to buy.
  

There are many ways to navigate and set destination in the Garmin Nuvi 255W GPS. You can set the location by address, telephone number, various points of interest (POI, such as those shown below), intersections, coordinates, etc.

This unit supports the "speak street name" feature, but you have to select a speaking voice that support for Text-to-speech (TTS) in order for this feature to function. There is one mandarin speaker voice which support TTS, but she will just spell out the name like "J-A-L-A-N ..." instead of pronouncing it as "Jalan ...". Anyhow, the American and British TTS are working well with Malaysian road names.