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Thread: A short GPS Primer

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    Senior Member Farmsky's Avatar
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    Default A short GPS Primer

    This information is littered with 'my opinions' on certain subjects and products. Reader beware

    - - - - - - - - -

    There are two fundamental forms of GPS mapping systems.

    Vector maps

    All 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 planning may be supported (depending on the product) via PC software. Vector maps may be routable ie they can be programmed to provide directions with '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 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 call iTopo. iTopo uses proprietary map encoding. A one off license of around $100 is required to convert maps to MemoryMap format.

    Raster maps are simply an 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 image. Raster maps are not routable. You can create routable tracks 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 paper mapping series is available in digital form.

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

    Many consider Des Newman's (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.

    Garmin

    As mentioned above, the beauty of Garmin over other GPS street navigators is that the map software is open source. That means that 3rd parties can produce Garmin compatible maps. Australian purchased, street navigation Garmins, come standard with Garmins City Navigator 2009 (new maps have just been released). 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 mapsets that will take you off-road with a Garmin. Garmin Topo is 1:100,000 map based with fixed 20m contours and is auto routing for remote tracks. Nice, however you cannot turn contours off, which may make the screen a bit busy at times. 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 is not auto routing.

    Shonky Maps is a wonderful (not auto routing) free mapset for all of Australia based on Natmap 250k data. Dooghan's Contours v2.0 is a free transparent overlay giving 10m contours for all of Aussie. You can meet them on this forum from time to time.

    The Open Street Map ( ) project (enthusiasts like you and me) is slowly but surely mapping Australia and this is providing . More .

    Hint: You'll need Mapsource so read a bit further on.

    Garmin screens are nice and bright!

    So there are a few good 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 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 uses a version of OziexplorerCE. It is excellent.

    VMS Touring

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

    The off-road (raster map based) navigator, iTopo is considered 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 on it's way and it promising big things for a little bundle.

    And lastly TomTom with ttMap

    Yup TomTom's gone raster. Check it out and on this forum.

    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.

    1. Download and install Garmin's Mapsource. how. It's free and legal. You can now view Garmin maps on your PC. Download and install if you want moving Garmin maps on your laptop in conjunction with your GPS or GPS mouse.

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

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

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

    And there's now a free 5m (yes 5m!) transparent 'contour only' map available Contours 3.0 and . Thanks Dooghan.

    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 are now available. Have a and see if your area is mapped. If not why not do some mapping.

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

    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 (gmapsupp.img) in there. Shonky 'gmapsupp.img' is a 413.95 Mb download (434,061,312 bytes).

    Other Free Stuff

    a fulsome list of the many free GPS applications available

    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 GPS. nRoute works readily with your handheld Garmin GPS (not a Nuvi), however you will require an emulator if your GPS device is non Garmin. There's good info in the forums on how to achieve this. is the latest commercial offering augmenting the older but free nRoute. Unfortunately, to date there is no Ausssie offering. OziExplorer is probably the best option for raster maps.

    - - - -

    Note: The downloads are quite large, so the use of a 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.

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

    If I have missed key info, data or products it was unintentional.
    Last edited by Farmsky; 01-09-09 at 07:09 PM. Reason: added ttMaps :)

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    Senior Member Farmsky's Avatar
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    City and town map details are derived from high resolution 'up to date' maps. Many other sources are employed to ensure relevant map data. As you move into the country areas the resolution of the map source generally decreases.

    So perhaps a few more images comparing 25k 'raster data' to Garmin City Navigator 2008 'vector data'.

    The two maps show images of Gloucester, NSW

    Mapsource view 500m zoom



    Ozi view at an equivalent zoom. It's a pretty handy map. Notice additional tracks and information showing on the raster map.



    It is my understanding (could well be wrong) that Garmin and Oztopo are derived from 100k map day in country areas.

    Anyhow, that's my rough take on GPS maps. I hope it's helpful.

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    Senior Member Farmsky's Avatar
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    How are maps sourced and made?

    Almost all maps are initially sourced from calibrated paper or digital images.

    A vector map maker starts with a paper or digital map in a particular scale. Roads, features pois etc are then converted to vector format. Digital maps are made up of many layers, each adding a particular layer of map features. These layers provide a convenient method for the map maker to utilise technology to do the conversion. However, any imperfections in the map will be transferred to the vector copy. Obviously the higher the resolution/ accuracy of the source map, then the higher the quality and accuracy of the vector map.

    The OSM project is a significant exception. It is mostly sourced from actual GPS data captured by GPS enthusiasts.

    Google maps is another which has undertaken large scale survey work. Although largely based on source map data, given the enormous effort that Google maps has expended in 'on the ground' mapping and street level photography, one could suspect that Google map quality and accuracy increasingly benefits from this 'on the ground' survey work.

    Sensis and Navteq, the two major Australian street navigation vector map makers, both claim on the ground survey teams which work to improve accuracy, however in my opinion, they're efforts are not on the scale of OSM and Google.

    A Vector Map Example

    Shonky Logics' maps are generated from an earlier GeoScience Natmap 250k map. It is licensed for non-commercial use. All of the features of the 250k map were faithfully converted to vector format. Additional information improves the map detail particularly for 'water related' features.

    You can view the Natmap 250k in OziExplorer (raster) or Shonky in Mapsource (vector) and yes ... they are identical.

    However as you zoom in the raster map, the images blur, whilst zooming in the vector map, maintains sharp images. Since the source data is 250k, zooming greater than that best viewed in Ozi will simply increase the error margin when in Mapsource.

    Perhaps a few pictures can help illustrate this effect. These series of pictures compare Shonkys' Garmin vector maps against their GeoScience raster map source. The two map views displayed below are PC images taken from Mapsource -Vector and OziExplorer - Raster.

    The area chosen is the tip of Cape York, Queensland

    Mapsource at 15 Km zoom



    Ozi at an equivalent zoom Compare the detail. Raster maps win out here.



    MapSource at 3Km zoom



    Ozi at an equivalant zoom Compare the detail. It's pretty much the same. In my opinion 'raster' gives the clearest view of the map and features at this zoom level.



    Mapsource at 700m zoom. Vector maps come into there own now, however beware mapping errors which become magnified.



    Ozi at an equivalent zoom. Notice the fuzz has set in. Not too good and you would probably not operate for long at this zoom level.


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    Senior Member Farmsky's Avatar
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    Maybe this little table, may better show the practical relationship between a paper map scale and Mapsource scale (zoom). A quality 1:10,000 map provides superb mapping detail displayed as a raster image.



    Maybe that helps, or maybe it's esoteric nonsense.

    Note: The table is not scientifically accurate (I made it with simple practical measurement), but it is enough to get you in the ball park.

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    Jesus ,someone was busy here...
    Good work !
    I can't fully agree on the Navteq/Sensis thing as I noticed that at least here in Victoria most of the bush tracks are on my Navteq powered N95 where all Sensis maps only show a green big nothing.
    Might be a different story in other parts ,but as you said before : that's my personal opinoin
    Compliments to yout thread here - I hope someone makes it "sticky".
    Tomtom GO730 ,Navcore 9.004 ,Bootloader 5.5256 ,Map :Australia 845.2661
    ttmaps and Tomplayer on 16GB SDHC class6
    Password for all my files: downunder

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    Wow top stuff farmsky, helpful for a newby like me. Thank you.

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    Thanks Farmsky,

    This has answered a lot of the questions that I never thought to ask.

    As far as Sensis verses Navteq here in SE Queensland there is certainly more detail in the country areas with Navteq, but the accuracy is awful (continuous recalculations on roads that have never been realigned, a roundabout in Ipswich was 200m further down the road than shown on the map and street numbering that is all over the place. Sensis may have less detail but is far more accurate.

    Cheers, Ian
    Any sufficiently advanced technology is indistinguishable from magic!

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    Quote Originally Posted by Farmsky View Post
    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.
    I'd have to agree with that statement.
    Here in the WA midwest, Navteq has roads and towns that Sensis doesn't.
    Navteq is my choice just for that alone.

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    Great work Farmsky. Quite an effort.

    Going to wade in on the Navteq/Sensis thing - if you want to navigate accurately in Tasmania, Navteq is the one. From other posts, it seems one of the problems with Sensis is it shows roads that were planned and never built. From Downunder's post it seems it is missing roads as well. I have an example of Sensis inaccuracy right here at home. It shows my driveway as a street running from my street right through the block to the street behind. Naturally, any GPS using Sensis data tries to route me down this non-existent stretch every time I leave home.

    I can also give many examples of where with Sensis data, an address is a best guess. Many times I have been taken to an address destination to find it is one or two blocks away from the actual address. I have found Navteq to be much better with addresses.

    Lastly, Navteq makes it easy to send them map corrections. The web page has an interactive map where you can mark the position of the correction you're posting, then select the nature of the correction from multiple choice descriptions. A generous comment box allows you to elaborate (I often paste links to Google Maps showing the correct information).

    The Sensis correction page is a nightmare and you are required to correct GPS data, online data or printed data separately.

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    Senior Member Farmsky's Avatar
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    Thanks for the kind response.

    Do you have links to the 'correction pages' for Navteq and Sensis?

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    Indeed I do.


    Navteq:


    Whereis=Sensis=Telstra:


    Interested to know which one people would rather work with.....

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    Default Shonkymaps link broken

    Your link to
    does not work any more.
    They no longer seem to support free downloads.

    Does anyone have a new link to download the gmapsupp.img file for Shonkymaps ?
    Last edited by Lofty2; 17-03-10 at 02:57 AM.

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    Senior Member Farmsky's Avatar
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    ????



    as it always was.

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    Despite the patronizing insinuation, Shonkymaps does NOT have the single .img file.
    It only has links to download the setup file etc, but does not give the single gmapsupp.img file to download.

    I have also downloaded the linux version but it just has all the individual .img files, not the single large gmapsupp.img file.

    As per your note :
    "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)."

    this file being the link.

  • 24-10-10, 01:00 AM

    Reason
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    Do some reading, download the single maps and join them together yourself then???

    Like I did.

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    Quote Originally Posted by MultiSlayer View Post
    Do some reading, download the single maps and join them together yourself then???

    Like I did.
    Paper maps are more accurate. GPS can make mistakes I have experienced many times.

  • 10-11-17, 03:59 PM


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