Handy GPS - Offline maps

The full version of HandyGPS supports the downloading of tiles from tile map servers, such as the Open Street Map (OSM) cycle map. The map tiles for a selected area can be stored on your Android phone or tablet. Then, when you're out of cell tower range, you can use these as a map background image, instead of the Google Map layers.

You can watch a YouTube video about this feature here.

How to download an offline map

There are two ways to download map tiles:
  1. The easiest way is to choose the "Manage offline maps" option from the menu on the Google Maps page. This will use the current map view extents, and compute the maximum zoom; or
  2. The other way is to choose the "Manage offline maps" option on the main page menu. This requires manual entry of the map extents and zoom.
Both methods will take you to the page shown below:



To use this page, you need to have either Wi-Fi or cellular data enabled. You can choose a tile server, enter a zoom value between 0 and 18 (where 18 is the most detailed), and enter the minimum and maximum latitude and longitude for the bounding rectangle of the area you want to download for offline use. Currently, the app is limited to downloading 100 tiles for performance reasons.

Pressing the "Download map tiles" button at the bottom will start the download. When the download is complete, the offline map tiles will automatically be enabled on the Google Maps page, as shown in the example below.

If you want to test the tile server with the current settings before downloading the map, press the "Test" button. This will attempt to open the tile image for the centre of the current view in a web browser.



Selecting the current offline map

The "manage maps" page also has a section at the top showing you which offline map is currently selected, since the app can only render one offline map at a time. To change the active map, choose it from this list.

Deleting an offline map

At the top of the "manage maps" page is a "Delete a map" button. Press this and choose the map you wish to delete. This will remove the sub-folder containing the map tiles for this area.

Choosing a different tile server

The "manage maps" page has a drop-down list to choose from several tiles servers, but you can also add your own, and enter any tile server URL you choose. The only requirement is that you use {zoom} or {z}, {x} and {y} for the parameters for zoom-level, column and row. Also, many tile servers have a choice of three or more URLs e.g. a, b, c. Choose one of these only.

Need some examples ? Click here for a list of some of the available tile servers.

How to georeference your own map image

If you have a .jpg or .png image of a map that you want to display in HandyGPS, simply create a sub-folder under HandyGPS/MapTiles with the name of the map e.g. "Gosford". Then copy the map image into this folder.

When you select this map from the list at the top of the "Manage offline maps" page, the app will prompt you to enter the lat/lon extents of the map and then it will be automatically displayed as an overlay on the Google Maps page.

If you don't know the lat/lon extents of your image, you can first use the Add > Image Overlay tool in Google Earth Pro on a PC to correctly locate the image, then view the location properties of the image overlay to see the lat/lon extents.

An example a map image registered using this approach is here, and you can see a video about how to do it here.

Please note that this approach will only work for map images which are less than about 1000 x 1000 pixels. Larger images will generally need to be tiled as described in the section below, which is a more complex process. If your image is large you can also resize it to be smaller, but of course you will lose resolution if you do this.

Also, some map images may not be able to be overlayed with a simple rectangular stretch, but will require the image to be warped instead. In such cases, you may need to use a GIS package such as QGIS to warp the image first. But, if you don't want to go to all the trouble of installing and learning a GIS package, a user of the app, Ken, has come up with another way using Google Earth Pro.

Converting KMZ image tiles for use in Handy GPS

If you have a KMZ file which shows a map in Google Earth by using a set of tiled images (such as those you can purchase from Tasmap), then you can follow the steps below to import the imagery into Handy GPS:
  1. Rename the .kmz file to have a .zip extension.
  2. Extract the contents of the zip file to a new folder e.g. "MyMap".
  3. Right click on one of the image files in the "images" sub-folder in Windows Explorer and choose Properties > Details to determine the image dimensions in pixels. Also check that the images are either JPGs or PNGs since TIF files cannot be used with HandyGPS. (If you have TIF data you would need to manually convert each file to a JPG).
  4. Download and run our Offline Map Tool for Windows.
  5. Press the "..." button and browse to the doc.kml file in your "MyMap" folder.
  6. Enter the image dimensions in pixels e.g. 1364 x 1020
  7. Press the "Generate Handy GPS map tiles" button.
  8. Rename the images sub-folder in your MyMap folder to a name that suits the location. e.g. "OverlandTrack"
  9. Copy the entire "OverlandTrack" folder into the HandyGPS/MapTiles folder on your phone.
  10. Open Handy GPS on your phone and select the map page.
  11. Press the menu button at the top-right and choose "Manage offline maps".
  12. Select your map folder e.g. "OverlandTrack", and then press the back button.
  13. The offline map for that area should now be visible as an overlay on the map page in Handy GPS. (Click here to see an example).


Want to know even more ? Click here for the low-level detail of how offline maps work, and how to tile your own map images...


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