Visualization of Water Services in Africa: Data Applications for Nexus Governance - Governing the Nexus: Water, Soil and Waste Resources Considering Global Change - page 191

Fig. 4 Geoelectrical profile measurements visualized in spatial relationship context (x-y-z axis).
The resistivity (colour-coded) is shown in relation to depth (x axis) and profile length (y axis),
which allows a (pseudo)-3D interpretation of the sub-surface

Remote sensing and ground-based spectroscopy is widely applied to contin-
uously measure and record the reflected or emitted radiation from the earth surface
(CCMEO 2014 ). A comprehensive summary of state-of-the-art remote sensing
technologies and methods is given by the Canada Centre for Mapping and Earth
Observation (CCMEO 2014 ), NASA ( http://nasa.gov ) and Melesse et al. ( 2007 ).
Mainly three types of remote sensing technologies are available: multispectral
(visible-near- (vis-NIR) to mid-infrared (vis-MIR)), radar and hyperspectral
remote sensing (CCMEO 2014 ). In general, hydrology remote sensing is applied
for mapping and monitoring of watersheds (e.g. flooding areas, river banks,
wetlands) and hydrological features [e.g. land cover classi

￿

cation, impervious
areas, topography, precipitation, spectral indices (wetness index, vegetation
index)] (Melesse et al. 2007 ). The measurement can be carried out ground- (e.g.
vis-NIR spectroscopy), air- or space-based (CCMEO 2014 ). All remote sensing
images require image pre-processing prior to visualization and further usage
(CCMEO 2014 ). All above-presented technologies might be applied for upscaling
of point measurements to larger scales. This can be done by assigning point
measurements to larger clusters (e.g. soil type) obtained by classi

cation of
remote sensing images or geophysical measurement results. Methods comprise:
multispectral remote sensing (mostly using vis-NIR spectral range), Radar (Radio
Detection and Ranging) , LiDAR (Light Detection and Ranging) (independent
from cloud coverage measurement of precipitation [e.g. tropical rain measure-
ment mission (TRMM)], heights [such as topography, vegetation height) and
water depth (CCMEO 2014 )], thermal remote sensing (measures the temperature
of the earth surface making it useful for hydrology in terms of mapping and
monitoring of water resources), ground-based and airborne vis - NIR spectroscopy
and hyperspectral remote sensing. Vis-NIR spectroscopy and hyperspectral
remote sensing are used to characterize in the field chemical and physical prop-

erties of soils (Stenberg et al. 2010 ; Viscarra Rossel et al. 2010 ), contaminations