An Introduction to the Physical Basis for Deriving River Information by Optical Remote Sensing - Fluvial Remote Sensing for Science and Management - page 64

Bathymetric accuracy:
depth retrieval residuals

Bathymetric precision:
contour interval width

200 200

150 150

100 100

50 50

0

0

0 20 40 60 80 100 120 0 20 40 60 80 100 120

Easting (m) Easting (m)

-0.1 -0.05 0

Depth residual (m)
(a)

0.05 0.1 0 0.02 0.04 0.06 0.08

Δ d c (693 nm) (m)

(b)

Figure 3.10 Application of the forward image model developed by Legleiter et al. (2009) to a gravel-bed river. A hyperspectral image
was simulated using topographic survey data for the channel reach of interest, technical specifications of the Airborne Imaging
Spectrometer for Applications (AISA), and radiative transfer models of the water column and atmosphere. The simulated image has
2m pixels and consists of 12-bit data. (a) Bathymetric accuracy is expressed in terms of depth retrieval residuals, or errors relative to
the known input bathymetry. (b) Bathymetric precision is expressed in terms of contour interval widths

Δ

d c , defined for the band
centered at 693 nm. Reprinted from Remote Sensing of Environment , 113, Legleiter, C.J. & Roberts, D.A., A forward image model for
passive optical remote sensing of river bathymetry, pp. 1025-1045, Copyright 2009, with permission from Elsevier.

'count', in the sense that they are represented in the final,
digital image data, they must be sufficient in number to
'fill up' the bin and induce a transition from one digital
number to the next; the depth of these bins is related to
the sensor's radiometric resolution. The signal of interest
is the population of photons that have interacted with the
river and reached the sensor, but the fidelity with which

this signal is recorded is determined by the manner in
which the imaging system collects and bins these photons.
This binning analogy highlights the tradeoffs that must be
made in selecting appropriate instrumentation for a par-
ticular remote sensing project, with some compromise
reached between spatial detail, spectral discrimination,
and radiometric sensitivity (Legleiter et al., 2004).