International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B4, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
PLANIALTIMETRIC EVALUATION OF A CARTOSAT-1 STEREO PAIR - CASE
STUDY: SÁO SEBASTIAO, SP, BRAZIL
R. S. Barros*, C. B. M. Cruz*, L. M. L. Rabaco®
"Departamento de Geografia, Instituto de Geociéncias, Universidade Federal do Rio de Janeiro.
Rua Athos da Silveira Ramos, 274 — Bl. I — Sala 012, CCMN, Cidade Universitaria — CEP 21941-590 — Rio de
Janeiro, Brasil — (rafael.barros, cmad)(Q)ufrj.br
®CENPES/Petrobras, Av. Horacio de Macedo 950 - Cidade Universitaria
CEP 21941-915 - Ilha do Fundäo - Rio de Janeiro — Brasil — lismaria@petrobras.com.br
Commission IV/3
Keywords: IRS-P5, DEM/DTM, Orthoimage, Accuracy, Cartography.
ABSTRACT:
It is noticed a significant increase in the development of orbital and airborne sensors that enable the extraction of three-dimensional
data. So, it's important the increment of studies about the quality of altimetric values derived from these sensors to verify if the
improvements implemented in the acquisition of data may influence the results. In this context, as part of a larger project that aims to
evaluate the accuracy of various sensors, this work aims to analysis the planialtimetric accuracy of DEM generated from Cartosat-1
stereo pair. The project was developed for an area near the city of Säo Sebastiäo, located in the basin of the North Coast of Säo Paulo
state, in Brasil. The relief in this area is very steep, with a predominance of dense forest vegetation, typical of the Atlantic Forest. All
points in this assessment have been established in the field, with the use of single frequency (L1) GNSS receivers, through static
relative positioning. In this work it was considered the Brazilian standard specifications (PEC, in Portuguese) for classification of
cartographic bases. Results may be considered very good and showed that Cartosat-1 orthoimage presents accuracy equivalent to
class B for 1:10.000 scale. The DEM presents altimetric accuracy compatible with class A of the 1:25.000 scale. Results obtained are
true for this specific area/study case, but may vary in case different scenes or other studies areas are considered.
1. INTRODUCTION
The improvement of products available to DEM and
Orthoimage production is very important for Brasil because it
may help cartographic updates, since most of Brazilian maps
were generated in the seventies and eighties. For many areas in
Brasil, cartography presents a lack of maps in larger and with
high details scales.
In this context, Cartosat-1 stereo pairs — or similar ones with a
good cost x benefit relationship — could contribute for
cartographic bases production, reaching scales not covered by
other sensors.
But since the use of those orbital data is something new, it is
important the increment of studies about the quality of
altimetric values (and also planimetric data) derived from these
sensors in order to verify if the improvements implemented on
data acquisition may influence results (Correia, 2008).
Cartographic products in Brasil should be evaluated,
considering a norm called Brazilian standard for cartography
accuracy (PEC, in Portuguese — Brasil, 1984). This norm
specifies that 90% of the points used in the assessment must
present errors and standard deviation till a predetermined
threshold (according to the scale). According to errors found,
the product may be classified as class A (higher accuracy), B or
C (lower accuracy) for each scale. Table 1 presents the limits of
the errors and standard deviation acceptable for scales 1:10,000
and 1:25,000, for planimetry. Table 2 presents the limits of
errors and standard deviations for scale 1:25,000 for altimetry.
1:10,000 1:25,000
Tol. (m) | SD (m) | Tol. (m) | SD (m)
Class A 5.0 3.0 12.5 7.5
Class B 8.0 5.0 20.0 12.5
Class C 10.0 6.0 25.0 15.0
Tol.: Tolerance; SD: Standard Deviation; m: meters
Table 1: Limit values used to classify cartographic products
according to PEC, for planimetry.
1:25,000
Tol.(m) SD (m)
Class A 5.0 3.3
Class B 6.0 4.0
Class C - 7.5 5.0
—
Tol.: Tolerance; SD: Standard Deviation; m: meters
Table 2: Limit values used to classify cartographic products
according to PEC, for altimetry.
1.1. Objectives
In this context, this work aims to analysis the planimetric
accuracy of an orthoimage and the altimetric accuracy of a
DEM (Digital Elevation Model) generated from a Cartosat-1
stereo pair, considering the Brazilian norm (PEC).
1.2. Study Area
The evaluation took place in an area near the municipality of
Säo Sebastiäo, located in the north coast of Säo Paulo state
(Southeast of Brasil). It is part of a mountains chain called Serra
do Mar that presents a great height difference between the top
and the bottom (around 1,300 meters) in this area that is quite
close to the sca. So, relief of the arca is very steep, with a
predominance of dense forest vegetation, typical of the Atlantic
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