Bushwalk Australia

With due respect, "the time it takes for the position to be related to the satellite, the satellite to process the signal then correlate position and send it back to earth" This statement is technically incorrect, the earth GPS unit doesn't send any signals to the satellites. The the GPS earth units only receive and process the received signals.

Biggles wrote:A GPS is never 100% accurate, and cannot be. At best, it is a very good guide! Dilution of Signal — the time it takes for the position to be related to the satellite, the satellite to process the signal then correlate position and send it back to earth means there are variations in accuracy (often BIG variations), ...

Hi Biggles, either you're confused about how a GPS works or I'm not understanding you. A GPS doesn’t communicate with satellites - it is a receiver only, not a transmitter. Have a look at https://spaceplace.nasa.gov/gps/en/

Dilution of Signal? Are you referring to (geometric) dilution of position? which is concerned with the (very small) variances in calculated position that can occur as a result of the positions of the 4 (or more) satellites needed for the GPS to calculate it's position. eg if all satellites are well west of the GPS vs evenly distributed around the GPS (eg N, E, W & overhead).

What does 100% accurate mean? We're bushwalkers - how accurate do you need? To the nearest few metres is more than sufficient & a GPS delivers that in all but extreme locations (in narrow gorges, bottom of cliffs etc).

Edit : sorry, rolv, didn't see your post.

Hi guys,

This discussion has gone off-topic. This thread is for OSM maps for Garmin GPS. Please strart, or use, anotger thread for general GPS discussion.

Thanks
Andrew

Hi all,

New version of all maps with current OSM data. No other changes.

By the way the link to the maps is on the first post, but just to repeat it:

http://tiny.cc/osm-maps

andrewp wrote:By the way the link to the maps is on the first post, but just to repeat it:

http://tiny.cc/osm-maps.

Andrew, link not working for me. 404 Error. So I assume the issue is that it is a http URL, not https.

But nevertheless, I thank of course, for providing the maps.

http://tiny.cc/osm-maps

dropped the period at the end

Thanks tastrax.

Thanks !

andrewp wrote:By the way the link to the maps is on the first post, but just to repeat it:

http://tiny.cc/osm-maps

Brilliant and thank you!

Hi all,

Another new version of all maps with current OSM data. No other changes.

Thanks Andrew.
Downloaded VicMap and OSM-maps from interwebby; both now on GPSMap64s.

Thanks as usual for your great work Andrew!
cheers

Hi all,

Another new version.
Rebuilt NSW, NT, QLD, SA, TAS, VIC, WA with new OSM data. Changes for Walls of Jerusalem (TAS).
Re-instated add-pois-to-areas for any polygons with tourism tags, mainly for huts and camps shown as a polygon, rather than a point.

Cheers
Andrew

Hi all,

Another new version.
Rebuilt NSW, NT, QLD, SA, TAS, VIC, WA with new OSM data.

Cheers
Andrew

Thanks, Andrew - much appreciated, as always.

Thanks Andrew. The combination of clearly displayed 10m contours and waterways plus OSM data is very useful for hikers.

These img maps work well in BaseCamp (which I use for route planning). Just place them in a USB drive (in a folder named Garmin) or use the virtual drive method described by JaVaWa at https://www.javawa.nl/virtualdevice.html.

They are probably equally good in a Garmin GPSr, but smartphones are now so good that I have not used my 60Cx for years. Oruxmaps on my phone does not do such a good job of displaying these img maps, even after tweaking OM settings under Map>Garmin. In OM, it is probably better to alternate between geopdf or WM(T)S maps from the State government sites and OSM maps from OpenAndro at https://www.openandromaps.org/en. The WM(T)S mosaic is lower in resolution, but easier near mapsheet edges (because OM can only load one geopdf at a time). OSM often has better tracks/footpads but take care as it also has errors. The government sites often include other useful topographic data. It is great to be able to flick back and forth between maps to build the best mental picture.

Off-track wrote:OSM maps from OpenAndro at https://www.openandromaps.org/en. The WM(T)S mosaic is lower in resolution, but easier near mapsheet edges (because OM can only load one geopdf at a time). OSM often has better tracks/footpads but take care as it also has errors.

OSM data can be corrected by anyone.
I like OSMand because the maps are updated monthly, so any corrected errors are gone in a month and any updated data is also there in a month.
OpenAndro maps update 4-5 times per year...

For OSM & other mapping buffs in TAS, Listmap Tasmania now has georeffed tiffs for historical air photos
Its a good way to check out old places for uo to 75 odd years ago. Thanks Listmap peeps !
https://nre.tas.gov.au/land-tasmania/ae ... hotography

These .img maps highlight the interesting problem that different states use different representations for map elements such as intermittent vs. perennial watercourses.
The difference is striking if one looks in the vicinity of adjoining Lamington NP (QLD) and Limpinwood NR (NSW).

Cartographers do not always capture what is in the field, and even the states seem to change the classification and/or definition of these things over time or in different map products.
Current Qtopo maps (and the .img map) show the Albert R as intermittent way upstream of the parts that most hikers would consider as perennial.
On the other hand, the .img map does not seem to follow the current spatial.nsw method of distinguishing these hydro-line types. (Except during heavy wet periods, hikers would need to follow some of the .img map solid/thick blue lines well downstream to find a trickle of water.)

I notice that the usual OSM topo maps often do a closer match to on-the-ground reality for waterways (not to mention consistency across state borders); but it is a bit uneven. The usual OSM topo maps have poorer contours than these .img maps.
Garmin Topo Australia (v5 in my installation) also does a good job of distinguishing watercourses that are perennial vs intermittent in a "normal" year.

This is a reasonably complex issue, especially once one gets to legal ramifications https://www.researchgate.net/publication/297442802_Up_the_creek_What_is_wrong_with_the_definition_of_a_river_in_New_South_Wales.

Off-track wrote:I notice that the usual OSM topo maps often do a closer match to on-the-ground reality for waterways (not to mention consistency across state borders); but it is a bit uneven.

Within OSM there is some different interpretations of 'seasonal' and 'intermittent'... And I tried to introduce 'ephemeral'. Renders (map makers) don't usually distinguish between 'seasonal' and 'intermittent' so the contributors interpretations don't actually go anywhere.

Of course there are entries from overseas who are not familiar with Oz and put perennial water where that should be intermittent .. I think I have all the major 'lakes' now correctly mapped as intermittent, though I'd rather have some as ephemeral. Your free to make corrections by simply registering on OSM.