This data can be delivered directly to the customer who can then develop it with their
own specialised information systems and in-house knowledge. Alternatively, Helica can
process the data into a "turn-key" product.

Helica's remotely sensed raw data comprises:
LiDAR Altimetry Data
Digital photography
Digital Videos
Hyperspectral Images
Thermal Images

Intensity

A laser intensity image directly represent the physical reflectance characteristics of the surface.
The Laser Scan systems used by Helica, send 33,000 to 167,000 coherent light pulses a second to the ground. For each pulse, both the point’s co-ordinates and it’s reflection are recorded. This allows for the physical characterisation of the object struck by the pulse, such as asphalt, rooftops, soil, vegetation, water etc. This data provides an initial classification of the surveyed points.

Points cloud

This is the set of all return pulses measured by the sensor, correlated with each pulse emitted.

This data comprises:

Geographical coordinates (x,y,z) of the return (position and height)
Intensity of the return
GPS Time

The plano-altimetric co-ordinates (x,y&z: latitude, longitude and elevation) are corrected during processing and combined with the position data obtained from the GPS Satellite receiver and the Inertial Unit (IMU).
Once the data from the Points cloud has been geometrically corrected and georeferenced, it is used to produce the digital surface models (DSM).

First - Last Pulse

A laser pulse emitted from an airborne sensor encounters various obstacles before it reaches the ground. The reflection events are therefore numerous. The ALTM 3033 System only records the first and last reflection for each laser pulse emitted. The ALTM 3100 System and the Gemini record up to 4 return pulses.

Digital Photos

Digital photos are taken at the same time as the laser-scan survey. The images are recorded in RAW/TIFF format with 4080 x 5440 pixels and a colour resolution of 24 or 48 bit RGB. The GPS time stamp of the image is recorded so that the single image can be georeferenced with the same process used for the Laser Scan points cloud.

Video

Videos can also be recorded during the survey flights. Images are geo-referenced: the video camera is connected to the onboard navigation system and the GPS time and geographical position on the WGS84 reference Geoid is added to each frame. These images are normally used for control and verification purposes but can also be used for further processing.