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Fulcrum Location Accuracy and Trimble Catalyst

February 12, 2019

Fulcrum is capable of recording location data with each parent record, child record, and media attachment. The location data collected is based on the configured location provider in the operating system on your mobile device. Typically this is the onboard GPS sensor, which is sometimes augmented by the other sensors and radios contained within the device.

In this post we’ll quickly review how each mobile OS calculates your location and then dive into Android-specific setup for utilizing the Trimble Catalyst antenna with the software-defined receiver to enable you to gather sub-meter location data on your Android phone or tablet.

Platform Specifics


By default, Fulcrum is using Google’s Fused Location API. This means that the OS is controlling data from sensors available and filtering the data from each to provide the “best” available location to any apps — in our case, Fulcrum. One potential issue with this API is that it is currently limited to reporting at best 3 meters of accuracy, even if the accuracy is actually better than 3 meters.


On iOS devices, Fulcrum is using the Apple Core Location API. Much like the Android Fused Location API, Core Location is controlling and filtering data streams from many sensors on the device providing the “best” location available to any apps that utilize this API.

A little background

Both frameworks use all available onboard hardware to gather data about the device’s location and generally simplify getting the best location source into an app for mobile developers. Currently, the GPS radios in the majority of consumers’ hands are capable of achieving 3 meter accuracy at best. This is usually sufficient for most Fulcrum users and their data collection use cases. However, when doing things like engineering-grade surveys or delineating wetlands where you need sub-meter accuracy it is possible to add an external GPS device to your data collection toolbox and achieve accuracy down to <10 centimeters in ideal conditions while still capturing all your attribute and media data inside of Fulcrum.

One such solution recently tested with Fulcrum is made by Trimble, and is using a software-defined receiver in an application that you can download to your Android device that is hooked up to an external antenna via the USB port on your phone. Once you have this antenna connected and Android configured to use the Catalyst software as a mock locations provider, then Fulcrum (and any other location-consuming apps) will use this external GNSS antenna as its data source.

If you’re curious about what a software-defined receiver is, follow this link to a quick, high-level overview of an open source software GNSS-SDR. It’s definitely over my head, but it’s helpful to think of it as: “the radio hardware has been replaced with software.”

Also check out our comprehensive guide to Bluetooth GPS devices for comparison of different products available.

Android & Trimble Catalyst Setup

The Trimble Catalyst only works with Android at this time. This is an example of a simple real-world application of gathering centimeter-level accuracy points using Fulcrum and the Catalyst receiver. These points were taken by placing the antenna at the center point of some ground control point markers made out of tent stakes and square pieces from a styrofoam cooler laid out on the ground. Using a DJI Mavic Pro drone, we flew a photo mission of about 50% of the town and post-processed the data utilizing OpenDroneMap’s new beta Lighting Network. (Here’s a post from our own @colemanm further discussing OpenDroneMap.)

The Setup

Things you’ll need:

ItemCostAndroid DeviceVariesCatalyst Reciever~$300Catalyst Subscription~$50-400/month

The cost of the Catalyst subscription varies depending on the accuracy you require. The good part is you can rent this on a monthly basis as needed for projects and pay for just the level you need.

Setting up your Android device with the Trimble Catalyst is fairly simple. It does require digging into the Android settings and enabling Developer Mode. You need to do this so that you can select a mock locations app (here are instructions from the Trimble Catalyst website). A mock locations app overrides the internal location provider.

Mock Location Settings

Once you have set up the Android OS settings, you can open up Fulcrum and dive into the settings to check that you are indeed capturing location data based on the data stream from the Trimble Catalyst device.

Fulcrum Location Debugger

You can now start capturing sub-meter accurate data in Fulcrum!

Pro-tip: Here is a link to an example Data Event that will display your location and accuracy inside a form.

Fulcrum is a data collection platform that enables businesses to reduce costs, access critical data in real time, and improve decision making at every level. With Fulcrum, you can create custom apps using our simple drag-and-drop builder to turn your paper documents into digital forms that your field teams can quickly complete on mobile devices.