GPS Primer Part 1

This is Wahroonga Farm's attempt to demystify the world of GPS.

Copied by permission from GPS Australia Forums

Wahroonga Farm wrote:

There are two fundamental forms of GPS mapping systems.

Vector maps


All 'turn by voice' street navigators use vector mapping. The streets, roads and landforms etc are encoded in software as points, lines, and polygons stored and displayed using their mathematical constructs. The advantage is that the map data (stored in memory or on SD card) is relatively small and the resulting image is crystal clear at any zoom level. As the zoom level is increased or decreased, map features are 'added or removed' automatically, so that screen clutter is managed. Map 'pre' and 'post' trip planning may be supported (depending on the product) via additional PC software. Vector maps may be routable or non-routable ie they can be programmed to automatically calculate a route from 'A' to 'B' and provide visual and audio 'turn by voice' directions.

Navteq or Sensis?


Australian vector mapping and poi data is produced by either 'Sensis' or 'Navteq'. The main GPS players; Garmin, TomTom and Navman use Sensis .... for a good reason. Sensis is the most accurate and up to date dataset; with better speed and lane information etc in the Cities, highways and rural areas. Navteq is claimed (by some) to have a better rural dataset. I have my doubts, however in all fairness they both have particular strengths and weaknesses. Navteq is the 'cheaper' map used by the low volume suppliers such as Mio, Navigon (it's an excellent street navigator btw) and the 'all so rans' such as R66 etc.

City street navigation vector maps are generally useless in the real bush. TomTom, Garmin, Mio, Navman, Navteq or Sensis, it makes no difference, they're all as good and bad as each other.

If you're up the Strzelecki .... you need an 'off road map'. Purpose made Australian off road topographical vector maps are currently available for Garmin and Magellan GPS's. Read more further on.

As Garmin's mapping format is open source, anyone can build a Garmin map. Now that's good news. A number of countries, with enthusiast support, have developed sophisticated free auto-routing Garmin maps. Singapore and New Zealand have developed leading edge free Garmin turn by voice vector maps.

However for most soft roaders, a standard issue street vector map will do the job just fine.

Raster maps


Many off road navigators deploy raster maps. The major raster mapping softwares used in Aussie are Oziexplorer (PC and car mount variants) as used by the Hema Navigator and MemoryMap. The VMS tourer uses a variant of MemoryMap called iTopo. iTopo (MemoryMap) uses proprietary map encoding. A one off license of around $100 is required to convert maps to MemoryMap format.

Raster maps are simply an electronic image of a paper map. They are viewed on screen as a moving map image. They are best viewed at only one zoom level for the sharpest picture. Raster maps are not routable. You can however create routable tracks/routes of your own.

However, anyone can make a raster map, so the mapping database is huge. 1:25k mapping (or better) where available, will give the very best track information and details. The full Hema Australia paper mapping series is available in digital form.

There are many free and commercial sources of quality raster mapping.

Many consider Des Newman's OziExplorer (PC version) and OziCe (PNA/PND version) to be the king of commercial raster GPS software. There are competitors (CompeGPS, Memorymap, Fugawi etc), however IMO Ozi is consistently the most featured and versatile of all.

Des is responsive to any niggles and has a steady release of new features. It's hard to beat, and it is Ozi!

Garmin


As mentioned above, the beauty of Garmin over other GPS street navigators is that the map encoding is open source. That means that 3rd parties can produce Garmin compatible maps.

Australian purchased, street navigation Garmins, come standard with Garmins City Navigator 2010. City Navigator is a Sensis mapping product, which is excellent for towns and cities. No good in the bush though, as noted above.

Oztopo and Garmin Topo are the two commercial Australian mapsets that will take you off-road with a Garmin. Garmin Topo is 1:100,000 map based with embedded 20m contours. It is auto routing for City areas and remote tracks. Nice. However you cannot turn the contours off, which may make the screen a bit busy at times. OzTopo's 10m contours, (and the ability to turn contours on and off to make maps easier to read (two mapsets) and 1:25,000 topo map detail makes OzTopo the current vector off road favourite for many. However it does not support auto routing.

Shonky Maps is a wonderful (non auto routing) free mapset for all of Australia based on Natmap 250k data. Dooghan's Contours v2.0 and v3.0 is a free transparent overlay giving 10m & 5m contours for all of Aussie. You can meet them on this forum from time to time.

The Open Street Map (OSM ) project (enthusiasts like you and me) is slowly but surely mapping Australia and this is capable of free auto routing mapping. More here.

Hint: You'll need Mapsource installed on your PC, so read a bit further on.

Garmin screens are nice and bright!

So there are a few sound reasons to buy Garmin.

Marine, Handheld, Bush walking and Geocaching GPS


This surprisingly, is a quite a spec_ialist area. Best to bone up and ask questions of the many expert enthusiasts here.

One street navigator perhaps worth a look at in this category (long battery life and waterproof) is the Garmin Nuvi 500.

Cross-over GPS's


These units run both vector and raster mapping software and maps. Brief information on a short selection of these units follows.

Chinese imported PNA's/ PND's will generally perform a cross-over function, as access to the WinCe operating system is straightforward; enabling access to the operation of raster and vector GPS software.

Hema Navigator


Not in your life. The street mapping software is Route 66. It uses (cheap) Navteq mapping and the GPS engine is simply horrible.

The off-road mapping GPS uses a version of OziexplorerCE. It is excellent.

VMS Touring


Well worth a look. It uses the excellent iGO8 street mapping software and Sensis vector mapping.

The off-road (raster map based) navigator, iTopo is considered by some to be a more intuitive system than OziExplorer for a beginner.

The VMS product can be purchased with an AV input for a rear view camera. Sweet!

Magellan Crossover


I'm no expert on Magellan GPS. You can purchase off-road Magellan topo mapping (vector format and said to be the very best topo map currently available) so that's a big plus, and like Garmin Topo it's Navteq based. 8 hour hand held, 'out of the car' battery life is a bonus.

CompeGPS TwoNav


Long awaited but it's now arrived. Nicko's promising big things for this little bundle.

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So now let's collect a bit of free stuff.

Garmins Mapsource


If you have a Garmin ... almost any Garmin street or handheld navigator .... or even if you don't; here's how to get hold of some nice free topographical maps for outback trip planning on your PC or laptop.

Download and install Garmin's Mapsource. You can now load and view Garmin maps on your PC. Download and install Garmin's nRoute if you want moving Garmin maps on your laptop in conjunction with your Garmin GPS or GPS mouse.

Mac users are not forgotten. Garmin's Roadtrip for Mac (free) will help you with maps and tracks 'n thing. Review here. After that review, I'm still confused, but then it's probably a Mac thing.

Shonky's Australian Topographic Maps


Download Shonkylogics free Garmin topographical maps of Australia. Here's some more info. It's a big download so best to use a download manager to ensure a corruption free download.

Note: If you only need Shonky maps, a 'quick and dirty' solution is to download the ready made version (there's no need to fiddle with Mapsource). Get hold of an SD card, create a folder in the root of the SD card called Garmin and place this file (gmapsupp.img) in there. Shonky 'gmapsupp.img' is a 413.95 Mb download (434,061,312 bytes).

You can plan and develop your own routes, tracks and waypoints in Mapsource for upload to your GPS.

Contours Australia v3


A free 5m transparent 'contour' map 'Contours Australia v3.0' is available from here.

It's a mighty effort and you can get it on DVD (see the 'download page'), for the tiny sum of A$6.00. The forum has further information.

It is computer interpolated from SRTM data (courtesy of NASA), which only has 90m resolution. As a result, a few funnies do creep in, particularly around sea level. Improved ASTGTM data (courtesy of Japan's ASTOR/Terra satellite) with 20m resolution has just been released. Watch this space. Thanks Dooghan.

OSM Australia


Shonky is great in the Aussie bush, but there is little detail in towns and cities. The OSM project is slowly mapping Australia and is very, very good for many city and town areas; not so good in the bush. Routable Garmin maps are now available for download and installation via Mapsource. Have a look and see if your area is mapped. If not why not do some mapping.

So how do I get these maps from Mapsource onto my Garmin?


To load these great maps and contours to your GPS via Mapsource have a look at this forum video tutorial .

Other Free Stuff


Here's a fulsome list of the many free GPS applications available.

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Moving maps on your lappie


Yeah the big screen! nRoute (free) enables moving map (and turn by voice directions with suitable maps) via your laptop or netbook coupled to a suitable Garmin GPS or Garmin mouse. nRoute works readily with your handheld Garmin GPS (not a Nuvi), however you will require an emulator if your GPS device or mouse is non-Garmin as nRoute requires Garmin proprietary GPS protocol to communicate. However there are emulator solutions, GPSGate and GPSProxy. There's no doubt more.

GPSGate appears to be most reliable.

Garmin Mobile PC is the latest commercial offering augmenting the older but free nRoute. Unfortunately, to date there is no Aussie offering. It looks and works like a Nuvi. You can even load and view multiple maps such as Contours and Shonky etc.

OziExplorer is probably the best option for raster maps. Any old GPS or mouse with a serial or usb interface will work here (but not a Nuvi).

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Note: The downloads are quite large, so the use of a download manager to ensure complete, error free downloads is highly recommended; 'Down Them All (Firefox)', Download Express, Free Download manager etc.

Now that lot'll keep you quite busy till tea time.

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Note: This is a quick off the top of my head primer.

If I have missed key info, data or products it was unintentional.

Please feel free to correct or add to this basic information.

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Have a read of Geosciences 'Map Reading Guide- How to use Topographic Maps'. It explains all the basics.



Download the 4.94Mb pdf here .

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