Geography Reference
In-Depth Information
4 m for the multispectral bands (blue, green, red and near infrared), and radiometric
resolution of 11 bits. Another novelty offered was the acquisition of the stereo pair in
the same orbit.
The Ikonos product used in this assessment comprises four scenes (two stereoscopic pairs),
in the GeoOrtho Kit mode (with RPCs - Rational Polynomial Coefficients), acquired on April
11, 2009. The assessment only used the panchromatic band.
Study area is located near the border between São Sebastião and Caraguatatuba, both
municipalities of the northern coastline of the state of São Paulo. This area is inserted in the
Serra do Mar (Sea Mountain Range), which in this area presents height differences of up to
800 m, with vegetable cover of the tropical forest type.
Scenes referring to the panchromatic band were modeled in Orthoengine 10.2, of PCI
Geomatics, making use of RPCs and seven GCPs (Ground Control Points). The orthoimage
was generated with the nominal resolution of the raw scene (1 m) and the DEM was
generated with resampling, taking the pixel to 2 m. For assessment, 32 points were used, all
surveyed with GNSS, through relative static positioning, with single frequency (L1) trackers.
Regarding planimetric accuracy, the results indicated the orthoimage as
class C for 1:2,000
scale
, having in view that 96.9% of the points used in the assessment presented errors of up
to 2 m and Standard Deviation (SD) of 0.5 m, demonstrating a very low internal error.
Regarding altimetric accuracy, the generated DEM from the panchromatic band could be
fitted in
class C for 1:10,000 scale
, because 91.2% of the points used presented errors of up to
3.75 m and SD of 2.0 m.
4.2. GEOEYE 1: Planialtimetric assessment of orthoimage and DEM
Images of the Geoeye satellite are among those with highest spatial resolution available at
present. The acquisition of stereoscopic pairs is also made along the same orbit. The sensor
presents a panchromatic band of 0.5 m spatial resolution and multispectral bands (blue,
green, red and near infrared) of 2.0 m spatial resolution, and radiometric resolution of 11
bits. The stereoscopic pairs used in this assessment where acquired with RPCs.
Study area comprises the Ilha Grande Island, located in the municipality of Angra dos Reis,
in the south of the state of Rio de Janeiro. The prevailing relief is mountainous, with a
vegetable cover of the tropical forest type, presenting height differences of up to 1,000 m.
The stereoscopic Geoeye pair, acquired on March 24, 2011, was modeled by Orthoengine
10.2 of PCI Geomatics, using RPCs, 6 GCP and seven Tie Points. For assessment 24 points
were used, all of which had their coordinates determined by relative static positioning,
using 2-frequency (L1L2) GNSS trackers.
The orthoimage, generated with nominal resolution of 0,5 m, presented planimetric
accuracy compatible with the specification, according to PEC, for
class B for 1:2,000 scale
,
since 90% of the points used in the assessment presented errors of up to 1 m and SD of 0.3
