Short answer: UgCS plans a terrain-following survey by flying each line at a constant height above the ground, using elevation data loaded before the flight. Every UgCS edition, from PRO up, does this. For very low flights, such as GPR, magnetometer and metal detector surveys, SPH Engineering adds True Terrain Following: the SkyHub onboard computer and a radar or laser altimeter hold the height live, as low as 0.5 m above the ground. Below is how to plan both, step by step.
Last updated: 24 October 2026.
Key takeaways
- Terrain following in UgCS uses a digital elevation model (DEM or DSM), so the drone keeps a constant height above terrain rather than above the take-off point.
- True Terrain Following (TTF) uses live altimeter readings through SkyHub, down to 0.5 m above ground, for low-flying sensors.
- Radar altimeter (US-D1): 0.5–50 m, works over water and in fog. Laser altimeter (SF30/D): practical range up to 100 m, but only 10 m over water, ice, snow and sand.
- UgCS works offline: cache maps and elevation for up to 100 km² per area before you leave for site.
- Line spacing and speed depend on the sensor. For MagNIMBUS, SPH recommends 0.5–1 m spacing at 2–6 m/s.
On flat ground, a drone flying at a fixed height above its take-off point is fine. On a slope, a hillside mine or a river valley, the same flight drifts closer to the ground in some places and far above it in others. Camera surveys lose consistent resolution, and low-flying geophysical sensors lose data altogether. Terrain following fixes this. These steps use UgCS, SPH Engineering's flight planning software, and follow the features SPH documents for it.
Two ways to follow terrain
| Terrain following (UgCS) | True Terrain Following (SkyHub + altimeter) | |
|---|---|---|
| How height is held | Route planned against elevation data loaded before the flight | Live altimeter readings adjust height during the flight |
| What you need | Any UgCS edition: PRO, EXPERT or ENTERPRISE | UgCS plus SkyHub, the SkyHub TTF package and a radar or laser altimeter |
| Typical height | Photogrammetry and LiDAR heights, where small DEM errors do not matter | As low as 0.5 m above ground, per SPH Engineering |
| Used for | Mapping, LiDAR, corridor and facade work over uneven ground | GPR, magnetometers, metal detectors, echo sounders over water |
| Limit | Only as good as the elevation data: trees, new spoil heaps or buildings not in the model are not seen | Needs the altimeter hardware on the drone |
Planning the survey, step by step
- Choose the method for your sensor. For an RGB camera or LiDAR over hills, UgCS terrain following is usually enough. For a sensor that must fly a metre or two above the ground, plan for True Terrain Following with SkyHub and an altimeter. SkyHub supports the DJI M400, M350 RTK and M300 RTK, and Pixhawk/Cube autopilots.
- Get the best elevation data you can. UgCS can use its default elevation data, but the plan is only as good as the model. Import your own DEM or DSM as a GeoTIFF where you have one. If you fly a mapping pass first, UgCS Mapper can produce a DSM in the field and send it straight to UgCS for the next flight.
- Cache the map before you travel. Survey sites in India often have no mobile signal. UgCS plans and flies without internet: cache the maps and elevation for the area beforehand (up to 100 km² per area, per SPH).
- Draw the area and pick the right tool. Draw the survey polygon, or import it from KML or CSV. Use the photogrammetry tool for cameras, and the Area Scan tool for geophysical and other non-camera sensors, so the lines are planned for the sensor rather than for a photo grid.
- Set height, line spacing and speed. Set the height above ground for the sensor and the terrain-following tolerance. Line spacing and speed come from the sensor maker: for the MagNIMBUS magnetometer, SPH recommends lines as close as 0.5 m for small items, 1 m for artillery-size items, and 2–6 m/s over typical farm fields. Single-beam echo sounders are towed at 0.5–0.7 m/s.
- Check the elevation profile. Before uploading, review the route's elevation profile in UgCS. Look for spots where the line clips a ridge, a tree line or a structure the elevation data may not show, and check no-fly zones and your flight-area limits.
- Set up the altimeter for True Terrain Following. With TTF, the SkyHub True Terrain Following package uses the altimeter to hold the height you set. Choose the altimeter for the surface: the US-D1 radar altimeter (0.5–50 m, IP67, works over water and in fog) or the SF30/D laser altimeter (practical range up to 100 m, but only 10 m over water, ice, snow and sand).
- Fly, monitor and split long jobs. Fly the mission from UgCS and watch telemetry and the sensor readout during the flight. For large areas, UgCS supports long routes with battery exchange, so a survey continues from where the last battery ended.
Which UgCS edition do you need?
Terrain following is included in UgCS PRO, UgCS EXPERT and UgCS ENTERPRISE. EXPERT adds SPH's automatic LiDAR tools (area, corridor and IMU calibration flights), and SPH bundles an EXPERT licence with systems such as the EchoNIMBUS-MBES. ENTERPRISE is for teams and service providers. If you are starting on PRO, upgrade licences exist, so you do not buy again. Compare them on the UgCS page.
Training
SPH Engineering runs UgCS courses from the basics through Area Scan and True Terrain Following, and HobiTech arranges them for Indian teams. See training and certification.
Sources: UgCS and SkyHub documentation and product data published by SPH Engineering; altimeter specifications from Ainstein and LightWare, as listed on each HobiTech product page.
Frequently asked questions
Does UgCS PRO do terrain following?
Yes. Terrain following against elevation data is included in UgCS PRO, EXPERT and ENTERPRISE.
What is True Terrain Following?
SPH Engineering's method for holding a constant height using live altimeter readings, processed by the SkyHub onboard computer. SPH states it works as low as 0.5 m above the ground, which suits GPR, magnetometer and metal detector surveys.
Radar or laser altimeter: which should I choose?
The US-D1 radar altimeter works from 0.5 to 50 m, over water and in fog, dust and rain. The SF30/D laser altimeter reaches further (practical range up to 100 m) but only about 10 m over water, ice, snow and sand. For water surveys, choose radar.
Can I import my own elevation model into UgCS?
Yes. UgCS imports DEM and DSM data and map overlays from GeoTIFF files, and routes or areas from KML, CSV and JSON.
Does UgCS work without internet?
Yes. Maps and elevation data can be cached for offline use, up to 100 km² per area, and missions are planned and flown without a connection.
Which drones does UgCS fly?
SPH lists DJI drones including the M350 RTK, M300 RTK, M30 and Mavic 3 Enterprise, plus Inspired Flight IF1200, Freefly and ArduPilot/PX4 drones. Tell us your model and we will confirm before you buy.
Planning a survey over difficult ground? Tell us the sensor and the drone, and we will suggest the licence and kit.
