GPS settings of road categories

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THE PROBLEM

In Garmin GPS there is a fixed road network classification, which includes the following 13 types:

  1. Major Highway
  2. Principal Highway 1,
  3. Principal Highway 2,
  4. Arterial Road 1,
  5. Arterial Road 2,
  6. Road,
  7. Alley,
  8. Ramp 1,
  9. Ramp 2,
  10. Unpaved Road,
  11. Highway Connector,
  12. Roundabout,
  13. Pedestrian

It is obvious that this categorization is adapted to Central Europe and USA standards, where the hierarchy of the road network is perfectly organized from the outset and continuously evaluated. Thus, the emphasis is on rational classification of the primary road network (e.g. there is the Major Highway Connector category, with no match in Greece and 2 ramp categories, whereas there is only one class of dirt road since in the western world dirt roads are private or forest roads and there use is prohibited or at least controlled).
Therefore, the one and only class of dirt road is restrictive for Greece, where 70% of the road network’s length is not coated and thus it is necessary to distinguish the following 6 types of non-paved roads:

1. Under blacktop road (TopoNavigator category 29),

2. Main road (TopoNavigator category 31),

3. Secondary patency dirt constant (TopoNavigator category 41),

4. Secondary dirt poor or changed patency (TopoNavigator category 42),

5. Gravel road of very poor patency (TopoNavigator category 50),

6. Broken road (TopoNavigator category 60).

The mismatch of the above image of Greek road with Garmin’s palette, reflects both on the symbolism of categories (where the dirt road category cannot be distinguished, compared with the TopoNavigator palette), and on routing calculation where the GPS will treat all dirt roads as being of the same viability. And indeed, this is what happens with the official Garmin maps (see AutoDrive Hellas etc), where the routing suggestion one gets, is more often impossible to be implemented.

THE SOLUTION

TopoNavigator5 relevant setting helps to dispel the above problem, by “stealing” two classes of the paved roads and giving them to the dirt roads. To preserve the compatibility with the Garmin classification system, TopoNavigator5 offers two options, which must be set BEFORE CONSTRUCTING the map.
(We note here that the choice of “Non Routable” in the relevant setting will create a file of about half a size that does not provide routing  parameters, but is very helpful for the older “hiking” models, where the routing is of little significance).
The first option (Figure 1) is the classic one that Garmin adopts and gives PRIORITY TO PAVED ROADS. The match of the 9 categories in use with the Greek reality is:

  • The motorways of the country (TN 11 & 12) are assigned to Garmin Class 1,
  • The Greek National Roads (TN 13 & 14) are assigned to Garmin Class 2,
  • Interregional routes (TN 20) assigned to Garmin Class 3,
  • The main asphalt provincial network (TN 21) assigned to Garmin Class 4,
  • All secondary roads coated (TN 22, 23) are assigned to Garmin Class 5,
  • Ramps (TN 25) mapped to Garmin Class 9,
  • All dirt roads categories (TN 31, 41, 42, & 50) are assigned to Garmin Class 10,
  • The secondary urban network (TN 83) mapped to Garmin Class 6,
  • Urban pedestrian (TN 85) mapped to Garmin Class 13

he second classification option (Figure 2) gives PRIORITY TO DIRT ROADS, by lending two categories of asphalts (not used in the first figure, since they are practically redundant) on dirt roads, increasing thereby the route options (11 categories), as the GPS perceives the two above mentioned dirt roads as asphalts and prefers them instead of the worse dirt roads categories. The matches are as follows:

  • The motorways of the country (TN 11 & 12) are assigned to Garmin Class 1,
  • The Greek National Roads (TN 13 & 14) are assigned to Garmin Class 2,
  • Interregional routes (TN 20) assigned the Garmin Class 3,
  • The main asphalt provincial network (TN 21) assigned the Garmin Class 4,
  • All secondary roads coated (TN 22, 23) are assigned to Garmin Class 5,
  • Ramps (TN 25) assigned to Garmin Class 9,
  • Roads in paved and dirt roads passable (TN 29, 31 & 41) are assigned to Garmin Class 7,
  • The dirt poor or variable viability (TN 42) assigned to Garmin Class 8,
  • The dirt only 4X4 (TN 50) assigned to Garmin Class 10,
  • The secondary urban network (TN 83) assigned to Garmin Class 6,
  • Urban pedestrian (TN 85) assigned to Garmin Class 13.

In Option 2, only the dirt roads that require a 4X4 vehicle are internally considered by the GPS as dirt roads and receive a similar treatment, while all others dirt roads are treated as low priority asphalts categories. The damaged roads, in Option 1 belong to the category of paths and in Figure 2 belong to the main paths.
Option 2 gives indirectly the ability for routing ONLY in good dirt roads (if, for example, a trip with a simple car), excluding the very poor dirt roads. The “trick” is that having “tricked” the GPS, by putting the good dirt in an asphalt category, it is sufficient to exclude from Garmin navigation settings the dirt roads (in general settings), so basically only the bad dirt roads are excluded. Thus, the navigation will look only on the good dirt roads, increasing our options.

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While loading the map, if you have chosen Option 1, you can choose Garmin palette (where you would have the symbols that Garmin intends for each model) or TopoNavigator palette, where you get symbols very similar to those on the computer screen. If instead you choose Option 2, you have to select TopoNavigator palette, otherwise you will have a complete mismatch in symbols (and tooltips on GPS) with the actual category of road.