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Hema Explorer [General] - Understanding Map Layers

Author: Robert Taylor Reference Number: AA-00313 Views: 10046 Created: 2014-04-28 20:37 Last Updated: 2019-04-18 08:39 75 Rating/ 6 Voters

The Hema Explorer app uses "map layers" to define which maps are viewable at certain zoom levels.

Each map layer has a defined zoom range (ie. minimum and maximum zoom level), as detailed in the table below.

Map Layer Name Provider / Source Minimum Zoom Level Maximum Zoom Level Approx. Max Scale
 Hema ExplorerHema516 *1:9000 
Cape York Hema 5 12 1:140,000
Fraser Island Hema 8 15 1:18,000
Great Desert Tracks (GDT) Hema 3 10 1:500,000
The Kimberley Hema 5 10 1:500,000
VIC High Country Hema 7 12 1:140,000
HERE TerrainHERE Maps0171:4,500
HERE StreetHERE Maps0201:1,000
HERE SatelliteHERE Maps0171:4,500
Geoscience 250kGeoscience Australia512 1:240,000
NSW TopoNSW Government Land & Property5191:1,100
QLD TopoQLD State Government5151:18,000
SA TopoSA State Government / TopoDude4151:18,000
TAS TopoState of Tasmania LIST5181:2,200
VIC TopoVIC State Goverment / TopoDude5151:18,000

* Hema Explorer can be accessed at a maximum zoom level of 12 in the Hema Explorer app. Purchasing a Pro subscription grants access to the maximum zoom level of 16.

Zoom levels roughly equate to a map scale, as per the table below.

Zoom Level Approximate Scale Metres / Pixel  Zoom Level Approximate Scale Metres / Pixel 
0 1 : 500 million 156,412  10 1 : 500,000 152.746
1 1 : 250 million 78,206  11 1 : 250,000 76.373
2 1 : 150 million 39,103 12 1 : 144,448 38.187
3 1 : 70 million 19,551 13 1 : 72,224 19.093
4 1 : 35 million 9,776  14 1 : 36,112 9.547
5 1 : 15 million 4,888 15 1 : 18,056 4.773
6 1 : 10 million 2,444 16 1 : 9,028 2.387
7 1 : 4 million 1,222 17 1 : 4,514 1.193
8
1 : 2 million 610.984 18 1 : 2,257  0.596
9 1 : 1 million 305.492 19 1 : 1,128 0.298

Notice that each zoom level also equates to a number of metres per on-screen pixel. This means that different screens having different screen densities (numbers of pixels per inch on screen) may show different apparent scales. So you may have a 10" Android tablet, and a friend has another 10" Android tablet. If you compare the same map layer, with the same zoom level, you may see some difference in the way the map appears on screen.

The best way to think about map layers is to imagine a stack of paper maps piled one on top of the others.

Each map layer has a defined zoom level range, and not all maps cover all zoom levels.

Map layer / zoom level examples

If you switch on the Zoom Label under Settings, it will help you to know what your current zoom level is.

The Hema Maps layers should be downloaded after installing the app. Once downloaded, they are available for offline use.

If you tried to download map layers covering the whole of Australia, at all zoom levels, the amount of data is astronomical, and not feasible. If you want access to the map layers for a specific area, you should download that area for offline use while you have an internet connection. (ie. prior to leaving on your trip).



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