This document provides an overview of ground truthing for remote sensing. It defines ground truth as observations or measurements made near the Earth's surface to support air or space-based remote sensing. Ground truth is collected using tools like GPS, radiometers, cameras, and topographic maps. It involves field observations, spectral measurements, location coordinates and sample collection to validate remote sensing data and reduce classification errors. The process of ground truthing helps verify pixel contents on satellite images and assess classification accuracy.

2. Contents-
 What is Ground Truth ?
 Ground truth collection for remote
sensing.
 Sources of ground truth.
 Ground trothing steps.
 GPS, Workflow of GPS, Radiometer,
Camera and tools, toposheets.
 Realisation of ground truth.
 Conclusion & References.

3. What is “Ground Truth” ?
 "Ground truth" is a term used in various
fields to refer to information provided by
direct observation (i.e. empirical evidence)
as opposed to information provided by
inference.
 This term is used in statistics and machine
learning that means checking the results of
machine learning for accuracy against the
real world.
 "Ground truth" is a term borrowed from
meteorology for independent confirmation
at a site for information obtained by remote
sensing

4. Ground truth collection for
Remote sensing -1
 Ground truth is simply observations or
measurements made at or near the
surface of the earth in support of the air or
spaced based remote sensing survey.
 It may also be referred to as ancillary data
or reference data.
 Ground truth may be consist of several
types of data acquired before, during and
after an image acquisition.

5. Sources of Ground Truth-
 Field observation.
 In situ spectral measurements.
 Aerial reconnaissance and
photography.
 Descriptive reports.
 Inventory tallies.
 Maps.
 Satellite data with various heights.

6.  Collect physical samples for laboratory
analysis of phenomena detected from
remote sensing data.
 Acquire supplementary non-remote
sensing data for interpretive model
analysis or for integration into Geographic
Information System.
 Develop standard sets of spectral
signatures by using ground based
instruments.
 Measure spectral and other physical
properties needed to stipulate
characteristics and parameters pertinent to
Ground trothing steps-

7. GPS(Global Positioning System)
 The GPS (Global Positioning
System) is a "constellation" of
approximately 30 well-
spaced satellites that orbit the
Earth and make it possible for
people with ground receivers to
pinpoint their geographic location.
 Using GPS device while ground truth data
collection, can help to determine real-time
location with acquired data that can be merged
both one and relate that actually the collected
data and located data being the same one or
not!

8. How does GPS work?
 There are three parts to a GPS system: a constellation
of between 24 and 32 solar-powered satellites orbiting
the earth in orbits at an altitude of approximately 20000
km, a master control station and four control and
monitoring stations and GPS receivers.
 The satellites sends microwave signals to a receiver,
these signals to work out ones precise distance from
each of the four satellites and then triangulates ones
exact position on the planet to the nearest based on
these distances.

9. Radiometer
 A new field radiometer has been developed
as a ground truth equipment for the optical
sensor. As a result of the preliminary
investigation, it has been shown that the
radiometer worked sufficiently well with
enough reliability in spectral measurements.
 Reliability of the radiometer was tested by comparing
the measurement results to the spectra obtained by the
high-resolution spectroradiometer over the same
targets. Using a radiometer the EMR radiation over a
ground can be trothed with sensed data.

10. Camera, tripods, robotic
poles
• Using various visible and invisible bands of
the electromagnetic spectrum, such
as infrared, gamma, or ultraviolet) and also geophysical
data enabling camera the remotely sensed data can be
groundly verified while on ground truth
• Another useful tool is tripod in ground
trothing to exactly level all the equipment
on ground using some level or GPS or
robotic poles
• Scales and notepad is strictly mandatory
while on survey

11. Topographic Map
 In modern mapping, a topographic map is
a type of map characterised by scale
details and quantitative representation of
relief, lines and variety of methods.
 This maps depict in
details ground relief,
drainage, forest cover,
administrative areas,
populated areas,
transportation routes
and facilities to correlate
with remote sensing

12. Ground truth in Meteorology-
 Ground truth is usually done on site, performing
surface observations and measurements of
various properties of the features on ground.
 It also involves taking geographic coordinates of
the ground resolution cell with GPS technology.
 Ground truth also helps with atmospheric
correction

13. Ground truth collection for
Remote Sensing - 2
 Correlate surface feature and locations as
known from familiar ground perspectives
with their expression in satellite imagery.
 Provide input & control during the first
stages of planning for analysis,
interpretation & applications of remote
sensing data.
 Reduces data and sampling requirements
for exploration, monitoring and inventory

14. Contd…
 Select test areas for aircraft and other
multistage support missions.
 Identify classes established by
unsupervised classifications.
 Select and categories training sites for
supervised classifications.
 Verify accuracy of classifications by using
quantitative statistical techniques.
 Obtain quantitative estimates relevant to
class distributions

15. Ground truth and realisation-
 Download of Data-
Choose a most convenient data to study.
 Area of workflow-
Choose experimental ground.
 Data acquisition-
Handle GPS, Radiometer, Scale and tableting
with valid information on ground zero.
 Digitization-
By classification, georeferencing and spectral
studies.
 Results-
Realisation and validation of data with on spot

16. Behind the “Ground Truth”
 It’s a fact that ‘Remote sensing is non
sense without ground truth’. From every
purpose of data validation its hardly
recommend to ground truth all the
remotely sensed data for best ever
result.
 Errors of commission and Errors of
omission- Ground truthing ensures that the
error matrices have a higher accuracy
percentage than would be the case if no pixels
were ground trothed. The process of ground
truthing helps to ensure that the pixel is

17. Conclusions-
 More specifically, ground truth may refer to a process in which
a pixel on a satellite image is compared to what is there in reality (at
the present time) in order to verify the contents of the pixel on the
image.
 In the case of a classified image, it allows supervised classification
to help determine the accuracy of the classification performed by
the remote sensing software and therefore minimize errors in the
classification such as errors of commission and errors of omission.
 Ground truth is usually done on site, performing surface
observations and measurements of various properties of the
features of the ground resolution cells that are being studied on the
remotely sensed digital image. It also involves taking geographic
coordinates of the ground resolution cell with GPS technology and
comparing those with the coordinates of the pixel being studied
provided by the remote sensing software to understand and analyse

18. Reference-
 Wikipedia.org
 Physics.org
 Remote sensing of the environment by
J. R. Jensen

19. Thanks for paying your
valuable attention…