# Terrain Informed Flight

{% hint style="success" %}
The app uses Google's [Elevation API](https://developers.google.com/maps/documentation/elevation/overview) to determine altitude offsets based on your drone's takeoff location.
{% endhint %}

***

## Motivations

* I want to maintain a consistent [Ground Sample Distance](https://support.pix4d.com/hc/en-us/articles/202559809-Ground-sampling-distance-GSD-in-photogrammetry) (GSD) during my flight.
* My [flight specification](/home/fieldagent-mobile-ios/faqs.md#data-collection-best-practices) requires TIF.

***

## Requirements

* You must have a [data connection](/home/fieldagent-mobile-ios/requirements/apple-devices.md#general) to build a TIF flight plan.
* [Flight Plan Export](/home/fieldagent-mobile-ios/60-second-guides/flight-plan-export.md) requires you to set your takeoff location **before** exporting.

***

## Steps

From the [Flight Planning](/home/fieldagent-mobile-ios/60-second-guides/fly-a-field-boundary.md) screen:

1. Tap on Terrain Informed under Options.

You can now tap on Review to see the altitude and elevation values.

**Additional steps are below**, depending on how you plan to execute your flight plan.

<figure><img src="/files/VNo5wBBJGPZV8SCCmYbj" alt=""><figcaption><p>Enabling TIF for your Flight Plan</p></figcaption></figure>

<table data-card-size="large" data-view="cards"><thead><tr><th></th><th data-hidden></th><th data-hidden></th><th data-hidden data-type="content-ref"></th><th data-hidden data-card-target data-type="content-ref"></th></tr></thead><tbody><tr><td>Are you flying a drone from the app?</td><td></td><td></td><td></td><td><a href="/pages/KkN3YfQPk4UBKAR2ulAY#fly-a-drone">/pages/KkN3YfQPk4UBKAR2ulAY#fly-a-drone</a></td></tr><tr><td>Are you exporting a flight plan?</td><td></td><td></td><td></td><td><a href="/pages/KkN3YfQPk4UBKAR2ulAY#flight-plan-export">/pages/KkN3YfQPk4UBKAR2ulAY#flight-plan-export</a></td></tr></tbody></table>

***

## Fly a Drone

You will be prompted to review the terrain and elevation values during the preflight check:

1. Tap on Accept on the top right.&#x20;

<figure><img src="/files/KMeN7bdkKdHwMDJDc18J" alt=""><figcaption><p>Verify Flight Plan</p></figcaption></figure>

{% hint style="success" %}
By tapping Accept, you take full responsibility for the drone's behavior during flight.&#x20;

The app provides TIF as a convenience.&#x20;
{% endhint %}

***

## Flight Plan Export

[Flight Plan Export](/home/fieldagent-mobile-ios/60-second-guides/flight-plan-export.md) supports TIF.&#x20;

### Requirements

* You must have your drone deployed at the desired takeoff location.
* You must have a [data connection](/home/fieldagent-mobile-ios/requirements/apple-devices.md#general).
* You must have [Location Services](https://support.apple.com/en-us/102647) enabled for the app.

### Steps

During export, you will be prompted to:

1. Deploy your drone at the desired takeoff location.
2. Hold your Apple device over the drone.
3. Tap Set Takeoff
4. Tap Accept

The export will then proceed normally.

{% hint style="warning" %}
**Do not** **move** **your drone** after specifying the takeoff location.
{% endhint %}

<figure><img src="/files/ONCU1JAwMXfltu4TeYqY" alt=""><figcaption><p>Set Takeoff for Flight Plan Export</p></figcaption></figure>

{% hint style="success" %}
By tapping Accept, you take full responsibility for the drone's behavior during flight.&#x20;

The app provides TIF as a convenience.&#x20;
{% endhint %}


---

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