The Electronic map vs the GPS map.
I often get asked what the difference is between an electronic map, usually loaded onto a PC, laptop or PDA; and a GPS map which is typically used on, or in conjunction with, a GPS receiver. Most people seem to think that they are one and the same thing and are also usually shocked when they learn of the price difference between the two. Here then is my (rather simplistic) explanation…
Electronic Map
This is simply an electronic version of a paper map with varying degrees of complexity, from a basic static image (which, when zoomed in, shows the same level of detail - just in a bigger size), to a map consisting of multiple overlaid images showing different levels of detail at different zoom levels. A basic electronic map can even be scanned from a paper map and then “geo-corrected” (a process of accurately fixing a coordinate grid to the electronic map).
Advantages:
- Electronic maps are relatively cheap and easy to produce which also makes updating them a rather painless and quick procedure.
- POI’s (Points of Interest) and attribute information such as street names can be embedded into the image as reference points to give the map a search capability.
Disadvantages:
- No auto routing capability (this is where the software can calculate which roads to travel on for the quickest or shortest route to your destination). This also means that you will not have any accurate calculations of how long the trip should take or your estimated time of arrival (ETA).
These maps can be loaded onto many electronic devices (including cellphones, PC’s, laptops, PDA’s and even GPS receivers) and, depending on the complexity of the map (as described above), will show varying levels of background detail on the screen. When used in conjunction with a GPS receiver, your position is then shown overlaid on top of the map and will move when you do. However, all routing and navigation instructions will be in a straight line, or “as the crow flies”, between your position and your destination end point (for both distance and direction).
GPS Map
Compared to the basic electronic map, a GPS map is a hugely complicated, resource intensive and expensive map to produce. These maps, similar to GIS (Geographic Information System) maps, are typically made up of multiple layers. Each layer consisting of a different type of information i.e. Country and Provincial boundary data, road data, POI data and even topographic and farm boundary data on some maps. Within the road data layer, each and every road is also broken down into segments which can range from a few meters to a few kilometers in length. Then, each road segment has embedded attributes or “properties” which could include information like:
- the name of the road (to which the segment belongs),
- the type and classification of the road (national, main, secondary, tertiary road etc),
- the type of road surface and condition (tar, gravel etc),
- the length of the road segment,
- the speed limit of the road segment,
- the direction of travel on that particular road segment,
- any street corners, intersections and off ramps & slipways that join/exit the road segment
- and much, much more.
All of this road segment data is needed for the GPS mapping software to be able to calculate the best roads to travel on for the quickest and/or shortest route between two points. This is what we call Autorouting or “intelligent routing” capability.
For example, on the “shortest route” setting, the software will work out all the possible combinations of road segments that could make up a route between your position (or start point) and your destination (or end point), calculate the lengths of the various road segments and then create a route using the combination of road segments that adds up to the shortest distance between the two points.
For the “quickest” (travel time) setting, the software has to do the same thing but this time taking into account the speed limit attribute attached to each road segment and work out which combination of road segments to use to create a route that would take the least time to travel between the two points (if driving at the posted speed limit).
Other properties of these GPS maps include embedded “triggers” for the production of the on-screen directions that are available on most “handheld outdoor” type of map enabled GPS receivers as well as the voice prompted turn by turn instructions on all “street navigator” type GPS receivers.
GPS Map Data Gathering Methodology
I recommend reading this article on the Garmap.co.za website describing the advantages and disadvantages of various methods of data collection for the production of GPS maps.
There are of course, a few other differences and features (of both types of map) that I have neglected to mention but, in the interests of keeping this article as simple as possible for the more “technically challenged” amongst us, I hope that my explanation is sufficient. Please ask any questions that you may have in the comments below and I’ll try and answer them without plunging into too much technical jargon.
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Your detail was very helpful. I have a question, what if a place do not have GPS maps.Are there companies who can do the job of making GPS map when we provide them map data.
Yes, but only if you have a busload of money to pay them
These maps are very expensive to make which is why they are not very commonly available for countries that do not have a substantial sized market (GPS owners) to pay for them.