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 layers on the mobile app is a completely different process from downloading layers on the desktop app. If you are looking for instructions on how to download 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 Layers?

The reason that you need to download 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 and overlays (such as the MapBuilder Topo base layer or the Public Lands overlay) in order to provide geographic reference.

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

Cached vs Downloaded Layers

Sometimes you may be able to view layers offline without downloading them first. This is because you are viewing cached 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 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 layers to your mobile device so you can easily use CalTopo offline!

Steps for Downloading Layers

Step 1 Choose Location

The first step is to choose where you want to download 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 layers for a particular map, center the entire map in the map viewer first.

If you would rather just download 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 Offline 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. By default, the quadrants that make up the area you were jut viewing will be outlined in yellow, indicating that they are pre-selected for download. You can deselect these quadrants or select additional quadrants as needed. How to select and deselect quadrants for download will be covered covered in the next step.

Download Layers page

The Show Coverage For drop down menu allows you to view the offline availability for different base layers and overlays. If a layer has coverage in an area, you will see that layer displayed on the page. For example, if you select Parcel Data from the Show Coverage For drop down menu, you will see the parcel data overlay displayed in any area where it is available for offline download.

Offline layer coverage for the parcel data overlay

If layers are unavailable offline for a particular quadrant, then the layer will not appear in that quadrant. This reflects only the availability of the layer selected in the Show Coverage For drop down menu. For example, the quadrants that are blank in the screenshot below do not have coverage for the Forest Service 2016 layer, which makes sense given that Forest Service maps are only available for US Forest Service and immediately adjacent land.

If the layer is missing from the quadrant when it is selected in the coverage menu, then it is not available for offline download in that area

Some layers, such as contours, are only displayed at higher zoom levels. Make sure to zoom in and out when you are checking for offline availability in an area.

Make sure to zoom in when you checking for offline coverage for layers like contours

Any quadrants that you have previously downloaded layers for will appear blue for standard resolution and purple for high resolution for the 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 tap on the quadrant. Quadrants you have selected will be outlined in yellow as shown below.

If you select a quadrant that you don't want, simply tap 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 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. Tap 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 your 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 Layers dialog will open. This is where 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 layers to download at that resolution for the selected quadrants.

For this example, let's select MapBuilder Topo and Global 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 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 remaining number of tiles left and file size will be displayed above the map.

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

You can navigate away from the Download Layers page if you'd like and the download will continue in the background as long as you have a good data connection. Tiles are built on demand by the server so downloads may take a little longer than they have in the past- make sure to give the app plenty of time to complete the download before you head out the door.

The quadrants will turn blue for standard resolution and purple for high or max resolution once the download is complete.

Blue indicates quadrants with standard resolution and purple indicates quadrants with high or max 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 the back arrow 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 Layers

Your downloaded layers will remain on your mobile device unless you delete them. To delete downloaded 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 layers, please follow the instructions described in Step 2 View Offline Layer Coverage for an Area above. Tap 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 dialog will appear with the number of files and size in the selected quadrants.

Choose which layers you wish to delete from the selected quadrant

Select Delete at the bottom of the dialog to delete all downloaded files in the selected quadrants. The Download Layers page will open again with the deleted quadrants no longer shaded blue or purple.

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

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