differences between satellite images by remote sensing and aerial photography

1. Aerial Vs Satellite Remote Sensing
S K Diwakar
Aerial Photography
Taking aerial photographs of the Earth's surface is a passive form of remote
sensing generated from cameras mounted on aircraft, satellites and other
spacecraft. The photographs are taken every 10 to 30 seconds as an aircraft
follows a systematic overlapping flight pattern at a fixed altitude. Each picture
slightly overlaps the preceding picture so that a stereoscopic (3-D) image of the
entire area can be produced and ground objects can be more easily interpreted
(note that a strict set of mathematical corrections are applied in an
aerotriangulation process prior to compilation to remove errors such as
atmospheric refraction, film shrinkage, and underwater refraction). NOAA's
primary aerial photographic product is a 9x9 inch color photograph, which is
usually exposed at scales from 1:10,000 to 1:50,000. NOAA photographers can
also capture images from select parts of the electromagnetic spectrum by using
various combinations of films and filters. The types of imagery they usually collect
include natural color, panchromatic (black-and-white), and false-color infrared
and black-and-white infrared photography.
Since the late 1930s, precision aerial photography has been the primary data
source for coastal survey maps, shoreline feature delineation maps, nautical
charts and other agency coastal geographical information systems. Unfortunately,
however, aerial photography has limitations in that it can only provide high
resolution spacial imagery when weather (e.g., cloud cover, sun angle) and
environmental (e.g., tidal) conditions are optimal.
Furthermore, the spectral sensitivity of aerial photography is limited to small
range from about near ultraviolet to near infrared. Therefore, Space agencies is
currently investigating existing and new remote sensing technology to augment
and/or replace conventional aerial photgrammetry. Unlike traditional aerial
photography, these techniques are able to capture images derived from a much
broader portion of the electromagnetic spectrum (from low-frequency radio
waves through gamma-ray regions of the spectrum) and in some cases are not
restricted by time of day, weather conditions, and other environmental
anomalies.

2. Aerial Vs Satellite Remote Sensing
S K Diwakar
Satellite Remote Sensing
Remote sensing is the science of remotely acquiring, processing,
interpreting and presenting spatial data for objects and environmental
processes using signals from a broad range within the electromagnetic
spectrum.
Remote sensing instruments are able to produce images of the physical
properties and characteristics of objects without being in physical contact
with them. Instead, this highly advanced technology forms images by
gathering, focusing, and recording reflected light from the sun, energy
emitted by the object itself, or reflected radar waves (which were emitted
by the satellite or other remote sensing devices). Therefore, remote
sensing can be further characterized as either “passive” or "active." Passive
remote sensing detects available (background) electromagnetic energy
from natural sources (such as sunlight), while active remote sensing,
depends on an artificial "light" source (such as radar) to illuminate the
scene.
NOAA uses digital photogrammetric work stations to produce numerous
remote sensing products, including shoreline vectors and maps, digital
elevation models, digital terrain models, airport layout diagrams, aviation
obstruction charts, and various other special use maps and products.
Furthermore, more advanced remote sensing technologies can be less
expensive than collecting the same type and quantity of data using aerial
photography and conventional ground survey techniques.
Satellite Imagery vs. Aerial Photography
Satellite imagery is an alternative to aerial photography but there is a lot
of confusion as to what is actually satellite and what is aerial photography.
Many people think that the data seen in Google Earth is taken from a
satellite when in reality it is high resolution digital aerial photography.
Similarly, many television shows, such as the BBC's Spooks, refers to their

3. S K Diwakar
imagery of towns and cities as satellite dat
photography supplied by Bluesky! So, what are the main differences
between the two and which would be most suited to your project?
Below is a list of benefits and weaknesses for both aerial photography and
satellite imagery. This information should help you make an informed decision
on the type most suited to your requirements.
Satellite imagery
Speed
Satellites are capable of collecting
large amounts of data in relatively
small amounts of time. A modern
satellite can be moved into position in
less than 3 days and can take the
photographs quickly once locked on to
an area. The size of these pictures are
very large and allow the complete area
to be captured using less images and
therefore, in a shorter space of time.
This is necessary with satellites as,
because of their limited
satellite may be required in a different
location very soon after.
Level of detail
Satellites generally reside several
hundred kilometers
surface. Although satellite imagery has
improved greatly over the years it is
still lower resolution than aerial
photography. High resolution satellite
imagery as high as 50cm per pixel is
readily available, up to 41cm in the case
of GeoEye-1 (however, the U.S.
Military requires resampling the
imagery to 50cm for all customers not
Aerial Vs Satellite Remote Sensing
imagery of towns and cities as satellite data when it is actually aerial
photography supplied by Bluesky! So, what are the main differences
between the two and which would be most suited to your project?
Below is a list of benefits and weaknesses for both aerial photography and
is information should help you make an informed decision
on the type most suited to your requirements.
Aerial photography
Satellites are capable of collecting
large amounts of data in relatively
small amounts of time. A modern
satellite can be moved into position in
less than 3 days and can take the
photographs quickly once locked on to
an area. The size of these pictures are
very large and allow the complete area
to be captured using less images and
therefore, in a shorter space of time.
This is necessary with satellites as,
because of their limited numbers, the
satellite may be required in a different
location very soon after.
Speed
Aerial photography
slow and time consuming process.
The amount of time taken to
capture an area depends greatly on
its size and shape. As airplanes fly
back and forth in 'runs' a series of
overlapping photographs are taken.
The dawn of digital aerial
photography cameras has made the
acquisition of airborne
photography considerably quicker.
However, the newest cameras are
making this faster still by
recording strips of data rather
than individual frames.
Satellites generally reside several
above the earth's
surface. Although satellite imagery has
improved greatly over the years it is
still lower resolution than aerial
High resolution satellite
imagery as high as 50cm per pixel is
readily available, up to 41cm in the case
1 (however, the U.S.
Military requires resampling the
imagery to 50cm for all customers not
Level of detail
Aerial photography has the
distinct advantage of having the
lens closer to the subject, in this
case the land. By adjusting the
flying height of the aircraft
capturing the data it is possible to
improve the detail that can be
captured. Most aerial photogra
was flown with a resolution of
between 50cm to 12.5cm per pixel.
With the new technology of aerial
Aerial Vs Satellite Remote Sensing
a when it is actually aerial
photography supplied by Bluesky! So, what are the main differences
between the two and which would be most suited to your project?
Below is a list of benefits and weaknesses for both aerial photography and
is information should help you make an informed decision
Aerial photography
Aerial photography used to be a
slow and time consuming process.
The amount of time taken to
capture an area depends greatly on
its size and shape. As airplanes fly
back and forth in 'runs' a series of
overlapping photographs are taken.
The dawn of digital aerial
cameras has made the
acquisition of airborne
photography considerably quicker.
However, the newest cameras are
making this faster still by
recording strips of data rather
than individual frames.
Level of detail
Aerial photography has the
distinct advantage of having the
lens closer to the subject, in this
case the land. By adjusting the
flying height of the aircraft
capturing the data it is possible to
improve the detail that can be
captured. Most aerial photography
was flown with a resolution of
between 50cm to 12.5cm per pixel.
With the new technology of aerial

4. S K Diwakar
explicitly granted a waiver by the U.S.
Government). Military satellites more
than likely have a higher resolution but
as yet this imagery has not become
publically available. Most off
satellite imagery is between 250m and
50cm in resolution.
Weather conditions
Both satellite imagery and aerial
photography can suffer from
environmental conditions. Being higher
up in the atmosphere means that
satellites have more weather
conditions to cope with. Thin cloud that
may not stop aerial photography can
still have a large effect on the quality
of satellite imagery. Due to its position
in orbit, and other requirements for
different areas the satellite may be
needed for another, clearer area. In
this case the window of opportunity for
photography may pass and it may be
some time before the satellite can be
repositioned. It is worth noting that
RADAR data is not affected by
weather conditions so can be collected
at any time.
Aerial Vs Satellite Remote Sensing
explicitly granted a waiver by the U.S.
t). Military satellites more
than likely have a higher resolution but
as yet this imagery has not become
publically available. Most off-the-shelf
satellite imagery is between 250m and
photographic cameras it is not
unusual for newer imagery to be
captured at 10cm per pixel. In
some cases this can be as low as
5cm or 2.5cm per pixel. Ho
these ultra-high resolution
datasets consume enormous
amounts of storage space and
consists of many times the number
of photographs than lower
resolution datasets. Also, having a
lower flying height enables
airborne acquired multi
and hyperspectral data to maintain
a higher resolution increasing its
potential uses.
Both satellite imagery and aerial
photography can suffer from
environmental conditions. Being higher
osphere means that
satellites have more weather
conditions to cope with. Thin cloud that
may not stop aerial photography can
still have a large effect on the quality
of satellite imagery. Due to its position
in orbit, and other requirements for
reas the satellite may be
needed for another, clearer area. In
this case the window of opportunity for
photography may pass and it may be
some time before the satellite can be
repositioned. It is worth noting that
RADAR data is not affected by
itions so can be collected
Weather conditions
Although aerial photography can
be affected by adverse weather
conditions there is still the
possibility of photographing areas
in thin or high level cloud which
might stop the use of satellites.
This has a small bearing on the
quality of the final imagery and can
normally be rectified during the
post-processing stage. There are
also far more planes available for
taking aerial photo
there are satellites so if one plane
is needed where the weather is
clearer then another may be
available to take its place. RADAR
is cloud penetrating so it is not
affected by adverse weather.
Aerial Vs Satellite Remote Sensing
photographic cameras it is not
unusual for newer imagery to be
captured at 10cm per pixel. In
some cases this can be as low as
5cm or 2.5cm per pixel. However,
high resolution
datasets consume enormous
amounts of storage space and
consists of many times the number
of photographs than lower
resolution datasets. Also, having a
lower flying height enables
airborne acquired multi-spectral
spectral data to maintain
a higher resolution increasing its
Weather conditions
Although aerial photography can
be affected by adverse weather
conditions there is still the
possibility of photographing areas
n thin or high level cloud which
might stop the use of satellites.
This has a small bearing on the
quality of the final imagery and can
normally be rectified during the
processing stage. There are
also far more planes available for
taking aerial photographs than
there are satellites so if one plane
is needed where the weather is
clearer then another may be
available to take its place. RADAR
is cloud penetrating so it is not
affected by adverse weather.

5. S K Diwakar
Types of data
Many modern satellites can collect a
variety of data. These include standard
photographic imagery, colour infrared
and in some cases LiDAR
radar data. This variety o
makes satellites very versatile.
However, non-standard data sources
such as thermal, LiDAR, multi
and hyperspectral imagery will likely be
expensive to capture or may not even
be publically available. The main
problem with satellite dat
that when new or improved technology
is released it is very difficult to
change the sensors and cameras in a
satellite but in a plane or helicopter it
is simply a case of removing the old
device and replacing it with the new
one.
Location
The major advantage of satellit
imagery is that the satellite can be
positioned to take imagery of anywhere
on the planet. It does not have to cross
borders or go through the many
passport controls that could delay a
visiting acquision team. Being above the
earth, it is more efficient
Aerial Vs Satellite Remote Sensing
Many modern satellites can collect a
variety of data. These include standard
photographic imagery, colour infrared
LiDAR, thermal,
radar data. This variety of datasets
makes satellites very versatile.
standard data sources
such as thermal, LiDAR, multi-spectral
and hyperspectral imagery will likely be
expensive to capture or may not even
be publically available. The main
problem with satellite data types is
that when new or improved technology
is released it is very difficult to
change the sensors and cameras in a
satellite but in a plane or helicopter it
is simply a case of removing the old
device and replacing it with the new
Types of data
Most aerial acquisition aircraft are
fitted with a mount that allows a
number of different cameras or
sensors to be attached to the
same aircraft. This allows the
swapping of capture devices but
only when the plane is not airborne.
Some aircraft can mount multiple
cameras or sensors and some of
the latest aerial cameras capture
different types of data
simultaneously, such as standard
imagery, radar and
Other datasets such as thermal
imaging requires the flying to be
performed at night so a plane that
was capturing standard imagery
during the day can be converted
during the evening and then sent
out again at night to capture
thermal data. Having a removable
sensor allows aerial acquisition to
keep abreast of the latest
developments in new technologies
and the cost of fitting these is
much lower than in satellites
orbiting many miles in orbit.
The major advantage of satellite
imagery is that the satellite can be
positioned to take imagery of anywhere
on the planet. It does not have to cross
borders or go through the many
passport controls that could delay a
visiting acquision team. Being above the
earth, it is more efficient for a
Location
Location can cause a delay for
aircraft acquisition teams. To
guarantee that the survey can be
completed an acquisition team
must remain on stand
the area to ensure that a weather
window is not missed. Luckily there
are many aerial companies aro
Aerial Vs Satellite Remote Sensing
Types of data
Most aerial acquisition aircraft are
fitted with a mount that allows a
number of different cameras or
sensors to be attached to the
same aircraft. This allows the
swapping of capture devices but
he plane is not airborne.
Some aircraft can mount multiple
cameras or sensors and some of
the latest aerial cameras capture
different types of data
simultaneously, such as standard
imagery, radar and colour infrared.
Other datasets such as thermal
imaging requires the flying to be
performed at night so a plane that
was capturing standard imagery
during the day can be converted
the evening and then sent
out again at night to capture
thermal data. Having a removable
sensor allows aerial acquisition to
keep abreast of the latest
developments in new technologies
and the cost of fitting these is
much lower than in satellites
many miles in orbit.
Location can cause a delay for
aircraft acquisition teams. To
guarantee that the survey can be
completed an acquisition team
must remain on stand-by near to
the area to ensure that a weather
window is not missed. Luckily there
are many aerial companies around

6. S K Diwakar
satellite to allow the earth to revolve
below it than to physically move to the
necessary location. Satellites still need
to take into account the location of the
sun to acquire visible light surveys so
many satellites try to remain in sun
synchronous orbit.
Post-processing
Imagery acquired by satellite usually
consists of far fewer "shots" than that
taken by aircraft. The extra distance
means that more area can be covered
in one pass - at the deficit of detail.
Satellites usually capture data in strips
(similar to a continua
area) and allow a larger amount of data
to be acquired per digital file. This
requires far less post
if it were to capture individual "frame"
images.
Aerial Vs Satellite Remote Sensing
satellite to allow the earth to revolve
below it than to physically move to the
necessary location. Satellites still need
to take into account the location of the
sun to acquire visible light surveys so
many satellites try to remain in sun-
the world who specialize
photographing their own country.
This means that for a company in
Australia to acquire photography
of the UK they only have to
contact one of the companies that
specialize in data of that area.
Imagery acquired by satellite usually
consists of far fewer "shots" than that
taken by aircraft. The extra distance
means that more area can be covered
at the deficit of detail.
Satellites usually capture data in strips
(similar to a continual video of the
area) and allow a larger amount of data
to be acquired per digital file. This
requires far less post-processing than
if it were to capture individual "frame"
Post-processing
Early aerial photography was made
up of tens of thousands
individual photographs. When the
aerial photography industry
adopted digital cameras each
digital file was a copy of what was
captured using analogue cameras.
Recent developments in aerial
camera design have moved away
from these traditional images and
moved towards the satellite's
method of capturing strips of
imagery instead. This has greatly
reduced the amount of post
processing work required but, with
it's lower flying height, there are
still more images than with the
higher flying satellites.
Aerial Vs Satellite Remote Sensing
specialize in
photographing their own country.
This means that for a company in
to acquire photography
of the UK they only have to
contact one of the companies that
in data of that area.
Early aerial photography was made
up of tens of thousands of
individual photographs. When the
aerial photography industry
cameras each
digital file was a copy of what was
captured using analogue cameras.
Recent developments in aerial
camera design have moved away
from these traditional images and
moved towards the satellite's
method of capturing strips of
imagery instead. This has greatly
reduced the amount of post-
processing work required but, with
it's lower flying height, there are
still more images than with the
higher flying satellites.