Geography Reference
In-Depth Information
transparency acts as a lightening and, according to Schweizer and Goodchild (
1992
)
and Leitner and Buttnefield (
2000
), affects perception of both noise level value and
uncertainty.
Due to fragmented nature of environmental noise data from the mobile mapping,
it is not possible to use contours (until observations are made on the vast part of the
area of interest) or symbol size (according to Senaratne et al.
2012
), because the
size of acoustically homogeneous areas is not equal and there may be a misinter-
pretation based on either inability to differentiate size of the area or on the basis of
overlapping symbols.
If the cells are tied to the street network [see Fig.
2(e)
], cells can be larger
because the noise is measured perpendicular to the source. Cartographic visualiza-
tion of the overall measurement uncertainty can be performed using the cell
s
texture. This will prevent misinterpretation of noise level by the map reader due
to transparency lightening. Cells also can be on both sides of street line, which
allows recording of asymmetric noise situations.
Because volunteers usually move along fixed routes (sidewalks, streets) when
measuring, cartographic visualization of noise level average values can be done by
using a line symbology.
Line hue
(or saturation) can then illustrate noise level,
line
structure
depict uncertainty [see Fig.
2(f)
].
Default and ideal for mapping by direct assignment of measured values to the
street line is a narrow street without lanes (Fig.
2
, 1). In narrow road with lanes is
traffic in different directions already reflected in the sidewalk
'
s noise levels (Fig.
2
,
2). For a wider street, which has more lanes, parking space for cars, intersections
with asymmetrically placed crossings, tramway lanes, etc. (depicted on Fig.
2
, 3), it
is useful to map each side completely separate.
Using uncertainty is possible to combine noise measurement data from static
measurement station with long-term measurements and calibrated noise meter. On
a typical raster map long term measurement is projected in one pixel, in the case of
an oriented cell it is possible to extrapolate its value (see Fig.
2
, 4). Short sections
that cannot to be recognized on a smaller scale maps may be generalized (see Fig.
2
,
5).
'
Adjustment of the Measured Data and Evaluation of Their
Uncertainties
During environmental noise measurement it is practically very difficult to deter-
mine the function of quantities of individual error sources. As a consequence,
standards ISO 3745:
2012
and ISO 1996-2:
2007
identify some of the most important
error sources: (1) Error in the measurement chain (sound level meter in the simplest
case, further denoted as
δ
slm
), (2) error due to the difference from the source ideal
operating conditions(
δ
sou
), (3) error due to meteorological conditions different from
