Using large maps

For maps in GIF or JPEG format, nhGPS will load the entire map image into the RAM memory of the phone. Although this results in fast performance, the size of such maps is limited by the available memory. On the P900 for example, the maximum map size for JPEG or GIF images is about 8 million pixels (e.g. 4000x2000) in 8bpp mode. Too large JPEG or GIF maps will cause Out of Memory errors in nhGPS.

To overcome this limitation, we have developed the proprietary MJP (Multi-resolution JPEG) file format. In an MJP file, the image is stored in chunks, and the MJP file contains separate layers for multiple resolutions. nhGPS dynamically loads and displays only the necessary chunks from the MJP file. As a result there are no limitations to the size of MJP maps, except for the space required on the memory card to store the MJP file itself. MJP files use JPEG compression with a selectable compression ratio.

MJP files are created using the nhGPS MJP converter, which can be downloaded below. In nhGPS, MJP files can be used in exactly the same way as JPEG or GIF images. All you have to do is convert your map image to .mjp format, in order to remove the size limitation.

To create an MJP based map in nhGPS:

1. On your PC, launch the nhGPS MJP converter
2. Choose Load Image and browse to the original map image (in JPEG or TIFF format)
3. Select the appropriate output quality (0=low, 100=high). Low quality will result in smaller files.
4. Choose Save .mjp to save the result
5. Transfer the resulting .mjp file to the phone
   (SonyEricsson's PC suite does not allow to transfer .mjp files to the 'images' folder, but you can place them in document\nhGPS instead).
6. In nhGPS, select New Map
7. Tap choose other... and browse to the .mjp file
8. Calibrate the map as you would do with other JPEG or GIF maps

Download and install nhGPS MJP converter (v1.2)
(1.0 MB, Windows only)