Offline Use


in this lesson

You can download and use the mobile app for free from the Apple or Google Play Store. However, if you wish to use the mobile app offline (which means in an area with no cell service or WiFi) then you will need a paid subscription.

The purpose of this lesson is to walk you through the steps for setting up the mobile app for offline use.

Topics on this Page:

Please note: Downloading base layers on the mobile app is a completely different process from downloading base layers on the desktop app. If you are looking for instructions on how to download base layers for offline use on the desktop app, those can be found in the Download and Sync lesson in the CalTopo Desktop chapter.

Why do I Need to Download Base Layers?

The reason that you need to download base layers is because what we call a “map” in CalTopo is actually just saved map objects at specific coordinates. Whether you have a data connection or not, you need to view those map objects on top of base layers (such as MapBuilder Topo or Forest Service layers) in order to provide geographic reference.

When you have a data connection, you can access those base layers in the Base Layers menu. However, when you don't have a data connection, you need to download base layer(s) for the map area to your mobile device in order to view and navigate around that particular map.

Cached vs Downloaded Base Layers

Sometimes you may be able to view base layers offline without downloading them first. This is because you are viewing cached base layer tiles. Cached tiles are tiles that are temporarily stored in CalTopo’s cache so that they can be quickly retrieved as you zoom in and out and pan around the map.

When you have a data connection, caching tiles greatly improves your experience because it increases the speed at which tiles load, providing a more consistent result as you move around the map.

When you have a data connection, cached tiles increase the tile loading speed, making for a better experience.

If you don’t have a data connection, you can sometimes still view recently cached tiles. However there are a number of problems with viewing cached tiles offline:

If you wish to use the mobile app offline then you need to download base layer tiles to your mobile device. Because these tiles are stored on your device, you can view and navigate around them even if you don’t have a data connection.

Now let's take a look at how to download base layers to your mobile device so you can easily use CalTopo offline!

Steps for Downloading Base Layers

Step 1 Choose Location

The first step is to choose where you want to download base layers on the map. If you have a specific map that you want to view offline, the first step is to open the map and center it in the map viewer. Make sure the entire map is in the map viewer. For example, let's say that I created a map for a multi-day backpacking trip through the Vogelsang Loop in Tuolumne Meadows. I would choose a zoom level that would allow me to see the entire map, as well as any other area I might be passing through, as shown below.

If you want to download base layers for a particular map, center the entire map in the map viewer first.

If you would rather just download base layers for a general area (i.e. the Wind River Range in Wyoming) rather than a specific map, you can also navigate to that area as well.

Step 2 View Base Layer Coverage for an Area

Navigate to the Download Layers page. Go to the three bar main menu in the upper left hand corner, and choose Download Layers.

Download Layers in the main menu

This will open the Download Layers page. The 15x15 minute grid laid over the map shows individual quadrants. You can zoom in or out and move around the map as you normally would on your mobile device. The perimeter of the area you were just viewing in the map viewer will be indicated by a purple dotted rectangle and any map objects will also be visible.

Download Layers page

The Show Coverage For drop down menu allows you to view the offline availability for different base layers. Some layers have limited geographic availability; for example the Forest Service layers are only available for US Forest Service and immediately adjacent terrain, and some aerial imagery layers do not have nationwide availability.

If layers are unavailable for a particular quadrant, it will be shaded red. This reflects only the availability of the layer selected in the Show Coverage For drop down menu. For example, the quadrants shown in red below do not have coverage for the Forest Service 2013 layer.

Red indicates that the base layer in the coverage dropdown menu is not available in that quadrant

Any quadrants that you have previously downloaded base layers for will appear blue for standard resolution and purple for high resolution for the base layer currently selected in the Show Coverage For drop down menu.

Step 3 Select Quadrants to Download

Once you have an idea what layers are available for the area you want to download, the next step is to select the quadrants you want to download.

To select quadrants that you want to download layers for, simply click on the quadrant. Quadrants you have selected will be outlined in yellow as shown below.

Click on a quadrant to select it. Selected quadrants will be outlined in yellow.

If you select a quadrant that you don't want, simply click it again to deselect it.

Make sure to select all the quadrants needed to cover the purple dotted rectangle if you are trying to get complete coverage for what you were just viewing in the map viewer (either a map or particular area).

Step 4 Select Base Layers to Download

Now that you have selected the quadrants you want to download, the next step is to select the layers you want to download for those quadrants. Click the download icon in the upper righthand corner.

With the default settings a popup will open as shown below and ask if you want to download on cellular if you are not connected to WiFi. Selecting OK will change you system settings for all downloads going forward and can incur carrier costs for downloading data. CalTopo is not responsible for any data costs incurred by users while downloading data.

Choose whether you want to allow cellular downloads

The download page will open. This is where base layers at a desired resolution can be chosen for download for the quadrants you selected. Choose between standard, high or max resolution from the resolution dropdown menu at the top of the page. Then select one or multiple base layers to download at that resolution for the selected quadrants. It will be noted in red font if a layer does not cover the entire area selected for download.

For this example, let's select MapBuilder Topo and NAIP 2012 Imagery at standard resolution.

Choose your resolution and layers for download

Download size is displayed at the bottom of the screen along with available device space and a visual representation of storage capacity. Be aware that downloading high resolutions of large areas will result in very large downloads.

Step 5 Download Your Base Layers

When you are happy with the layers and resolutions that you have selected, select Download at the button of the screen. The Download Layers page will open again and the map tiles for the selected areas will download. The quadrants will turn blue for standard resolution and purple for high or max resolution once the download is complete.

Downloaded base layer coverage will be indicated by blue or purple depending on the resolution

You can return to the Download Layers page at any time to check which layers you have downloaded in particular areas.

To return to the map viewer, press Map in the upper left hand corner of the screen. You can now view synced maps without a data connection in areas where you have downloaded base layers!

Deleting Downloaded Base Layers

Your downloaded base layers will remain on your mobile device unless you delete them. To delete downloaded base layers, go to the 3 bar menu in the upper left hand corner of the map viewer. Choose Download Layers from the menu that appears. The Download Layers page will open again.

To view where you have coverage for particular base layers, please follow the instructions described in Step 2 View Base Layer Coverage for an Area above.

Click on the quadrants you wish to delete layers from. The selected quadrants will be outlined in yellow.

Select the quadrants you wish to delete downloaded layers from. Selected quadrants will be outlined in yellow.

Then select Delete from the upper lefthand corner.

The Delete Tiles page will appear with all the base layers currently downloaded for the selected quadrants. Select the base layer(s) you wish to delete from the selected quadrants.

Choose which layers you wish to delete from the selected quadrant

Select Delete at the bottom of the screen. The Download Layers page will open again with the quadrants will no longer be shaded blue or purple for the deleted base layers.

Deleted layers will no longer show coverage on the Download Layers page

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