Methali (proverb)
Hajikwai
mtu kwenye mlima, hujikwaa kwenye kilima cha fuko.
Translation:
People do not stumble over a mountain, they stumble over a molehill.
"It's
easier for a person to stumble over an insignificant matter than over a
significant one."
Mlima
- mount, mountain: Mlima Kilimanjaro - Mount Kilimanjaro (normative)
Kilima
- hill, barrow, hummock, knoll, mound. (diminutive)
Attrition
warfare is a military strategy consisting of belligerent attempts to win a war
by wearing down the enemy to the point of collapse through continuous losses in
personnel, materiel, and morale. The word attrition comes from the Latin root ‘atterere’,
meaning "to rub against", similar to the "grinding down" of
the opponent's forces in attrition warfare. Attrition warfare represents an
attempt to grind down an opponent's ability to make war by destroying their
military resources by any means including guerrilla warfare, people's war,
scorched earth and all kind of battles apart from a decisive battle. Attrition
warfare does not include all kinds of Blitzkrieg or using concentration of
force and a decisive battle to win. In Blitzkrieg, the side that reinforces
their army at a higher speed will normally win the war, but attrition relies on
gradual weighing down of the opponent. Clausewitz called it the exhaustion of
the adversary.
Clausewitz
stressed the dialectical interaction of diverse factors, noting how unexpected
developments unfolding under the "fog of war" (i.e., in the face of
incomplete, dubious, and often erroneous information and great fear, doubt, and
excitement) call for rapid decisions by alert commanders. He saw history as a
vital check on erudite abstractions that did not accord with experience. In
contrast to the work of Antoine-Henri Jomini, he argued that war could not be
quantified or reduced to only mapwork, geometry, and graphs. Clausewitz had
many aphorisms, of which the most famous is "War is the continuation of
policy with other means."
LIDAR/LiDAR and InSAR data
LIDAR,
LiDAR or LADAR, an acronym of "light detection and ranging" or
"laser imaging, detection, and ranging", is a method for determining distances
by targeting an object or a surface with a laser and measuring the time for the
reflected light to return to the receiver.
InSAR,
an acronym of Interferometric synthetic aperture radar, is a radar technique
that uses two or more synthetic aperture radar (SAR) images to generate maps of
surface deformation or digital elevation, using differences in the phase of the
waves returning to the satellite. The technique can potentially measure
millimetre-scale changes in deformation over spans of days to years. It has
applications for geophysical monitoring of natural hazards, for example
earthquakes, volcanoes and landslides, and in structural engineering, in
particular monitoring of subsidence and structural stability.
Looking
at the example of landslides, both lidar and insar data may be used to generate
optical imagery for the measurement of segmentation using pixels and scale.
This data is used to calculate the average-shift segmentation, or simply, the
average distance of movement of sediment in a particular area. To calculate the
movement, two factors are used. They are labelled the “scar” (origin/source of
sediment), and the “deposit” (point of settling of the debris). Investigation
of the scar in accordance with various factors of soil weakness such as
geology, precipitation, slope, seismic activity, sedimentation history, and so
forth, determine the susceptibility of an area to landslide. Investigation of
the deposit in accordance with factors of soil movement like geology,
sedimentation history, and slope, determine the hazard of an area to being
covered in debris from another place.
LiDAR vs InSAR
They
are two differing technologies and as such, have very different advantages and
disadvantages. Usefully:
1.
Both
techniques can be employed during day and night, but only InSAR is effective in
all weather conditions. Rain, especially, is a problem to LiDAR sensors –
droplets can reflect and absorb some of the emitted light beam, degrading their
performance.
2.
LiDAR
produces ultra-high resolution, precise imagery thanks to technology that
provides x, y and z coordinates – the production of 3D representations of
elevations is easy since it uses a single frequency for image production. InSAR
is a form of radar which means the antenna transmits multi-frequency microwave radiation
that is reflected from the image area, as opposed to passive sensing, where the
reflection is detected from single-frequency radiation. The resultant image is
therefore a band of spectral colours.
3.
The
InSAR system has lower spatial resolution, or processing that introduces a bias
to lower-curvature surfaces. The Digital Elevation Model of LiDAR is more
accurate than the InSAR DEM, with less bias and less variance in significantly
higher-curvature surfaces. This simply means that InSAR is more suited to
measurement of smaller slopes where movement is minimal due to its fewer pixels
while LiDAR is more suited to measurement of larger slopes after a major
significant soil movement. InSAR is able to measure surface changes almost as
subtle as those detected by individual GPS stations (of less than 1 millimetre)
across terrain thousands of kilometres wide.
References:
Burgmann, R.; Rosen, P.A.;
Fielding, E.J. (2000), "Synthetic aperture radar interferometry to measure
Earth's surface topography and its deformation", Annual Review of Earth
and Planetary Sciences, vol. 28, pp. 169–209
Clausewitz, Carl von (1873).
On War
Hanssen, Ramon F. (2001),
Radar Interferometry: Data Interpretation and Error Analysis, Kluwer Academic
https://satsense.com/news/lidar-vs-insar.
Retrieved 24th nov 2023
Massonnet, D.; Feigl, K. L.
(1998), "Radar interferometry and its application to changes in the
earth's surface", Rev. Geophys., vol. 36, no. 4, pp. 441–500,
Travis S. Taylor (2019).
Introduction to Laser Science and Engineering. CRC Press.
TUKI (2001), Kamusi Ya
Kiswahili-Kiingereza; Swahili-English Dictionary. Published by Taasisi ya
Uchunguzi wa Kiswahili (TUKI), Chuo Kikuu cha Dar es Salaam, Tanzania.
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