MAP DISPLAY FORMATS

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POI's

POI is an acronym for Points of Interest. These are specific locations on the map that are deemed to have significance for the user. This information may be added or referenced on either type of map or could even been supplied separately as a database when no map is used at all. If you show a lot of poi's on the screen the user can interpret this data as if it were a crude map.

POI data can represent anything and serve several purposes. For example a search database for a raster map might have the locations of the words in the raster map coded into the database. The user could search the database and the program would use the location found in the database to display that location on the map itself. Used in this fashion a raster map would seem to have intelligence for the user in that he/she should find objects shown on the map.

Often a POI data is used to display icons directly on the map for the user to see. These icons provide significant value add for some users of the map. They can be as simple as a dot or as complex and a full drawing of a building. They can display the top of a mountain, or other geographic feature locations. They can also display the location of man made objects. The location may also be adjusted in some cases to fall on a road. The database containing the poi data might also include reference data that is not displayed on the map. For example the user might click on a map poi to bring up a text display screen showing detailed data about that location. For a restaurant the information might include the type of restaurant and even a telephone number for reservations.

POI data can also have a text label. This label information could be part of the icon but is usually separate. It can often be displayed in several locations near the object to which it is attached or might even be removed from the display entirely depending on the user preferences or program needs.

Conclusions

At this point in time all gps receivers use vector databases because of their inherent flexibility and reduced size. Computers (desktop, laptop, and palm sized) have some vector programs and some bitmap programs. This provides the user with a choice, particularly in parts of the world where vector databases of mapping data do not exist or are not available. One should not conclude that vector maps are inherently better. Bitmap maps can certainly preserve both the accuracy and beauty that was in the original map makers craft. Programs like Topo! have shown that you can take bitmap maps along with a underlying database that provide name search and altitude data to present, to the user, the best of both worlds. Even with this effort there can be errors where the underlying database information does not match the display, a problem that generally does not occur with vector maps. Delorme has released a set of topographical maps that include both vector and bitmap maps.

Garmin, Magellan, and Lowrance have all released vector maps for their respective units. None of these are interchangeable and no other software can be used to upload map data to these units, except that you can modify the maps by adding vectors to the maps in the Lowrance units using third party programs. There is a program available from another third party that can be used to create maps for Garmin units. There are other, more expensive, systems that can support the uploading of your own vector maps as a supported feature by the manufacturer. For example, Trimble makes a professional model that can be used to generate maps in the first place and can load and display these maps. Unfortunately you must always supply your own source of maps with this unit.

Vector maps can provide a lot of detailed road data but can be hard to prune the map to serve as road maps. Generally they work well for large areas only if you can remove all of the street level detail from the database. Some units even have multiple databases which are switched based on the zoom level. Bitmap maps can provide coverage for large areas with a minimum of space but will start to take significant space if you expect to be able to vary the detail by zooming. Both map types have their purpose as witnessed by the Delorme mapping product, Solus Pro, that supports both types in the same program.

revision

Dale DePriest

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