ACRI-IN owns a Trimble GPS that we use to perform
topographical surveys of a terrain. The data collected is used to
develop a map which graphically represents the elements surveyed
such as buildings, roads, vegetation, as well as variations in the
level of the land (altimetry). A 3D Digital Terrain Model (DTM) can
be generated from the data using software.
To get
precision down to the centimeter, we use real time "RTK" surveys: a
fixed GPS is placed in a reference (known x, y, and z coordinates)
or unreferenced location, which continuously records its position. A
mobile GPS connected by radio to the fixed GPS is used for the
topographical survey. This combination gives a precision down to 1
cm horizontally and 2 cm vertically.
ACRI IN owns an Ohmex Sonarmite single beam echo
sounder that performs precise bathymetric studies of the ocean
floor. The data collected is then used to create a digital terrain
model (in 3D).
Using the same principle as for the
topographical survey, the sounder is connected to a mobile GPS
located on a boat. This combination lets us survey depths over a
working range of 0.30 m to 75 m of depth with a sounder precision of
+/- 2.5 cm, and a GPS precision on the order of 1 cm horizontally
and 2 cm vertically.
