Hammer is an adaptive flight planner for DJI drones that allows you to capture quick and precise data for a number of different tasks, ensuring both ease-of-use and mission flexibility.
In this tutorial we will focus on how to use Terrain Follow in Hammer — a feature which allows collecting more accurate data for mapping/3D modelling hilly areas / sites by altering mission altitudes to maintain a constant GSD (ground sampling distance).
Note: This feature currently requires an internet connection OR a custom Digital Elevation/Surface Model (DEM/DSM) file in geotiff format.
Steps to Create
This guide assumes you are already familiar with creating mapping/3D modelling missions in Hammer. If not, please visit: 2D/3D Aerial Mapping in Hammer.
To create a terrain-follow mission:
- Create a mapping/double-mapping mission/magnetic mission as normal.
- Tap on the gear on the mission and configure settings.
- Switch Terrain-Awareness setting to ‘On’
- Choose whether you’d like to use NASA SRTM data — default, which has a resolution of 30–90m or if you’d like to import your custom DEM model with a higher resolution (recommended)
- Select the DEM file on your iPAD and tap Import. Then Press Done.
Hammer will prompt you to choose a takeoff location for the flight.
Pick the expected take off location so that Hamer can download the terrain’s elevation profile and replan the flight taking the elevation profile of the mission and takeoff elevation into account. You’ll notice the constant altitude on the mission (e.g. 50m) change to a dynamic range of altitudes (e.g. 51m →99m)
These altitudes indicate the lowest and highest altitude in the mission, required to keep a constant GSD. Feel free to adjust the flight altitude and overlap, which would trigger Hammer to replan the mission with a new altitude range.
Steps to Visualise
Note: It’s important that you have Google Earth for iOS installed on your device.
Once you are happy with the altitude range, it’s best to visualise the mission using Google Earth. Tap on the ‘3D View’ to export the planned mission and select ‘Google Earth’ from the list of apps that pop up.
You’ll see the planned mission as follows:
Feel free to navigate back to Hammer, make adjustments to your mission and re-visualise the mission till you are happy with it. Sometimes, the calculated flight altitude might exceed 120m (400ft) and drop under 0m, please make sure you are compliant with the drone flight laws in your country of operation.
Steps to Fly
To fly the mission:
- Load the mission from the saved missions menu
- Now tap on the wrench and set the appropriate Go Home Height. Please set this value to higher than the highest obstacle / terrain in your environment.
- Finally turn on your drone and position it exactly on top of the chosen takeoff location in the mission. Then turn restart the drone to capture the new home position. Finally, check mission altitudes and GoHome Height are correctly set up.
- When all checked, press Play to Fly.
- Terrain Data: It’s important to note that terrain information is not always accurate and therefore can sometimes have discrepancies from the real world. Please make sure calculated flight altitudes are safe before flying.
- Go Home Height: Please also make sure your GoHome Height is set to higher than the highest terrain altitude in your environment.
- Flight Altitudes: Lastly, calculated terrain altitudes might sometimes exceed 120m (flying limit in most countries). Please ensure your planned flight is compliant with the flying regulations in your country of operation. Also, please set your takeoff location appropriately to avoid negative altitudes.
- Max Height Settings: Please make sure the max. altitude setting in Hammer’s overall settings is set to higher than the highest altitude in the mission.
NOTE: If your mission is expected to take more than 1 battery, Hammer will fly the drone to the configured Go Home Height after every battery change to avoid hills / vertical structures in the flight path. Please make sure your Go Home height is set to higher than the highest altitude in the generated flight plan.
And that’s it! A few simple steps to create, visualise and fly a terrain-aware flight for mapping missions in Hammer. If you currently do not have access to the iOS app, feel free to contact us at email@example.com or download the app from the App store.
If you’d like to learn more about other missions supported in Hammer, please visit https://medium.com/@hammermissions