**5.1. Cartosat-1: Planialtimetric assessment of orthoimage and DEM**

The Cartosat-1 satellite - or IRS P5 - is aimed for cartographic applications, especially reference applications, for having only a panchromatic band, but with 2 different acquisition angles in the same passage. Its radiometric resolution is of 10 bits.

The stereoscopic pair analyzed covers the surroundings of São Sebastião, the same area mentioned before.

The stereoscopic pair, acquired on May 23, 2009, was processed with Orthoengine 10.2, by PCI Geomatics, using RPCs, with 7 GCPs and 8 Tie Points. The orthoimage was generated with nominal resolution equal to the rated resolution (2.5 m) and the DEM was resampled for 10 m. For assessment 30 points were used. All points were surveyed with GNSS equipment, with relative static positioning, with single frequency trackers.

The results were quite satisfactory, with the orthoimage reaching **a class B for 1:10,000 scale**, with 93.3% of the points presenting errors of up to 8 m and SD of 2.7 m. Altimetric accuracy was compatible with the specification for a **class A for 1:25,000 scale**, since 94.1% of the assessment points presented errors of up to 5 m and SD of 2.8 m.

#### **5.2. ALOS/PRISM: Planialtimetric assessment of orthoimage and DEM**

PRISM sensor onboard ALOS1 satellite acquired data only into panchromatic band, but with telescopes in three different incidence angles (Backward, Nadir and Forward), with a spatial resolution of 2.5 m. Operating in this mode, called Triplet, it presented optimal conditions for DEM generation, considering that different view combinations could be used, according to relief variation or any other needs.

PRISM data, likewise those from AVNIR2 were distributed by IBGE (*Brazilian Institute for Geography and Statistics)* to noncommercial users for much lower prices than those practiced by the market for compatible products. It explains the interest in such data and the need for assessments.

The results presented here referred to the assessment report of PRISM data in [16] and the work presented by some IBGE employees in [17], who assessed the accuracy of the geometry from a PRISM Triplet acquired with a 1B2R processing level covering the surroundings of the municipality of Itaguaí, in Rio de Janeiro.

The data was processed by Orthoengine 10.1, of PCI, without RPCs, but using 7 GCPs and 11 Tie Points. The orthoimage was generated with a Nadir view of 2.5 m and the DEM was

<sup>1</sup> ALOS satellite experienced trouble in April 2011 and was disconnected in May of the same year.

generated using the backward and forward views, resampled for 10 m. For assessment ends, 88 points were used, whose coordinates were determined by relative static positioning, making use of double frequency GNSS trackers.

The authors initially made a planimetric accuracy assessment of an orthoimage generated with 7 GCPs and SRTMDEM. The results showed that, even using a SRTM DEM, with 90 m pixels, the orthoimage would be compatible with an indication for **class A for 1:25,000 scale**, since the 40 points used in this initial assessment presented errors of up to 9.6 m, with SD of 2.1 m. Subsequently, the assessment was complemented using a DEM generated from the Triplet PRISM data. The results were also satisfactory and similar to those obtained with Cartosat1. The orthoimage presented planimetric accuracy compatible with **class B for 1:10,000 scale**, despite the authors' mentioning only attendance to scale 1 to 25,000 (which was the target of the assessment), since all points presented errors up to 7.9 m and SD of 1.9 m. The altimetric accuracy of the **DEM** was compatible with **class A for 1:25,000 scale** since 92% of the assessment points presented errors of up to 5 m and SD of 2.3 m.

## **6. Scales 1:50,000 or less**

188 Cartography – A Tool for Spatial Analysis

**5. 1:25,000 scale** 

mentioned before.

first return (that lead to the DEM generation).

is possible that there was a better treatment of the point cloud during data processing regarding the last return (responsible for DTM generation) in detriment of the data of the

The Cartosat-1 satellite - or IRS P5 - is aimed for cartographic applications, especially reference applications, for having only a panchromatic band, but with 2 different acquisition

The stereoscopic pair analyzed covers the surroundings of São Sebastião, the same area

The stereoscopic pair, acquired on May 23, 2009, was processed with Orthoengine 10.2, by PCI Geomatics, using RPCs, with 7 GCPs and 8 Tie Points. The orthoimage was generated with nominal resolution equal to the rated resolution (2.5 m) and the DEM was resampled for 10 m. For assessment 30 points were used. All points were surveyed with GNSS

The results were quite satisfactory, with the orthoimage reaching **a class B for 1:10,000 scale**, with 93.3% of the points presenting errors of up to 8 m and SD of 2.7 m. Altimetric accuracy was compatible with the specification for a **class A for 1:25,000 scale**, since 94.1% of the

PRISM sensor onboard ALOS1 satellite acquired data only into panchromatic band, but with telescopes in three different incidence angles (Backward, Nadir and Forward), with a spatial resolution of 2.5 m. Operating in this mode, called Triplet, it presented optimal conditions for DEM generation, considering that different view combinations could be used, according

PRISM data, likewise those from AVNIR2 were distributed by IBGE (*Brazilian Institute for Geography and Statistics)* to noncommercial users for much lower prices than those practiced by the market for compatible products. It explains the interest in such data and the need for

The results presented here referred to the assessment report of PRISM data in [16] and the work presented by some IBGE employees in [17], who assessed the accuracy of the geometry from a PRISM Triplet acquired with a 1B2R processing level covering the

The data was processed by Orthoengine 10.1, of PCI, without RPCs, but using 7 GCPs and 11 Tie Points. The orthoimage was generated with a Nadir view of 2.5 m and the DEM was

**5.1. Cartosat-1: Planialtimetric assessment of orthoimage and DEM** 

equipment, with relative static positioning, with single frequency trackers.

**5.2. ALOS/PRISM: Planialtimetric assessment of orthoimage and DEM** 

assessment points presented errors of up to 5 m and SD of 2.8 m.

surroundings of the municipality of Itaguaí, in Rio de Janeiro.

1 ALOS satellite experienced trouble in April 2011 and was disconnected in May of the same year.

to relief variation or any other needs.

assessments.

angles in the same passage. Its radiometric resolution is of 10 bits.

#### **6.1. SRTM DEM: Altimetric assessment**

The DEMs generated from the data of this mission by NGA (National Geospatial Intelligence Agency), NASA (National Aeronautics and Space Administration), have been widely used in Brazil - as well as in other countries - for being free, of good quality and with almost global coverage. Since its first divulging, in version 1, the immense potential for its use was perceived, mainly in locations without altimetric data of better quality and coverage in digital media. In function of the different versions available, four of them were chosen to be evaluated:


The assessment was made in the same way for the four versions, with small variation in the number of assessment points (between 90 and 92 points, depending on the DEM version) -

all surveyed with GNSS, through relative static positioning, with single frequency trackers in function of the variation of the pixel size and the coastline. The study area corresponds to part of the municipality of São Sebastião on the north coast of the state of São Paulo, in southeast Brazil.

Contribution of New Sensors to Cartography 191

 With ENVI / ASTER MDT: using the same scenes (same date), with the same processing level and control points; and using the same scene, however with L1B processing level

The orthoimages and DEMs generated for assessment had the same resolution as raw data: 15 m, despite having carried out tests of the DEM with pixels resampled up to 60 m,

There was no disagreement between the results obtained for planimetry, placing the VNIR orthoimages in **class A for 1:50,000 scale**, with 92.7% of the 41 assessment points presenting

In the case of altimetry, however, results were different depending on the approach used in DEM generation. Using Orthoengine, the worst results were obtained, since DEM meets the specifications for **class A for 1:100,00 scale**, with 94.2% of the assessment points presenting errors of up to 25 m, with a standard deviation of 10.5 m. When using the **ENVI /ASTERDTM,** with the same scenes, processing level and same 12 control points, the result changes to a **class C for 1:50,000 scale**, with 92.7% of the assessment points presenting errors of up to 15 m, with standard deviation of 8.6 m. Using the scenes with processing level L1B with **ENVI /ASTERDTM,** without any ground control point, the specification for a **class C for 1:50,000 scale** is reached, with 96.3% of the 41 assessment points presenting errors of up

These results ensued a questioning to the PCI representative in Brazil, with forwarding of all the data used, being answered by PCI that there was no failure or problem. It is therefore understood that the ASTERDTM modeling - which is a specialized ASTER module - is more

The ALOS/AVNIR-2 data, as well as those of the PRISM sensor of the same satellite, are of great interest for Brazil, since its data was distributed by IBGE (*Instituto Brasileiro de Geografia e Estatística*) for noncommercial users at a much lower price than those practiced by the market for products with the same features. It remained to know its accuracy in order to be able to fully explore its real capacity. The AVNIR-2 sensor acquired data in 4 spectral bands (blue, green, red and near infrared) with a spatial resolution of 10 m. Since the satellite contained a very advanced set of orbital and altitude control systems, its use would

The results presented here refer to the work published by a group of IBGE employees in [19]

Orthoimage was generated in Orthoengine 10.2, by PCI, with a resolution of 10 m, based on a scene acquired with processing level 1B2R, making use of seven ground control points and DEM SRTM version 4.0. The control points and the 34 assessment points were obtained from orthoimages in scale 1:25,000 generated by IBGE from photos in the scale 1:35,000. This

**6.3. ALOS/AVNIR-2: Planimetric assessment of orthoimage** 

be very appropriate both for reference as for thematic cartography.

who assessed the orthoimage geometry of this sensor.

and without control points.

without perceiving significant difference.

to 15 m, with a standard deviation of 6.1 m.

appropriate.

errors of up to 40 m, with a standard deviation of 11.6 m.

Table 2 presents a summary of the assessment results from the SRTM DEM in the four versions. In it, the number of assessment points used in each product are shown, as well as the percentages of points with errors up to the limit for a **class C for scale 1:50,000** (15 m) and **class A for scale 1:100,000** (25 m) as well as the Standard Deviation (SD) of each set of points used in the assessment for each DEM SRTM version.


**Table 2.** Summary of assessments of the 4 versions of DEM SRTM

From the results presented in table 2 one perceives that versions 1, 2 and 4 have very similar performances and present altimetric accuracy very near to the limits indicated for **class C of scale 1:50,000**. Only Topodata is indicated only for **class A of scale 1:100,000**. As the main objective of Topodata is to obtain a better detailing of the morphometric information derived from SRTM DEM, a small loss of accuracy is tolerated in favor to gain better detailing of the morphometric representation. Additionally, the goal and SD observed should be emphasized, mainly in versions 1, 2 and 4, showing that the DEM SRTM presents homogeneity and consistency in results.

#### **6.2. ASTER/VNIR: Planialtimetric assessment of the orthoimage and DEM**

ASTER images (Advanced Spaceborn Emission and Reflection Radiometer), onboard Earth satellite, are very interesting for being of low-cost and providing good spectral resolution, besides allowing the generation of DEMs from the stereoscopic pair of the VNIR (Visible and Near Infrared) sensor. This sensor provides a spatial resolution of 15 m, counting with the green, red and near infrared bands (the latter being acquired with two different incidence angles in a same satellite passage). Due to these features, those images can be useful both for thematic as for reference cartography.

Study area again was the vicinities of the municipality of São Sebastião. An assessment was carried out based on the results made from the images and DEMs generated according to two different approaches:

 With Orthoengine 10.2 by PCI Geomatics based on 2 scenes (same date) acquired September 19, 2008, with processing level L1A, making use of 12 control points and 9 Tie Points per scene.

 With ENVI / ASTER MDT: using the same scenes (same date), with the same processing level and control points; and using the same scene, however with L1B processing level and without control points.

190 Cartography – A Tool for Spatial Analysis

**DEM SRTM** 

homogeneity and consistency in results.

two different approaches:

Tie Points per scene.

useful both for thematic as for reference cartography.

southeast Brazil.

all surveyed with GNSS, through relative static positioning, with single frequency trackers in function of the variation of the pixel size and the coastline. The study area corresponds to part of the municipality of São Sebastião on the north coast of the state of São Paulo, in

Table 2 presents a summary of the assessment results from the SRTM DEM in the four versions. In it, the number of assessment points used in each product are shown, as well as the percentages of points with errors up to the limit for a **class C for scale 1:50,000** (15 m) and **class A for scale 1:100,000** (25 m) as well as the Standard Deviation (SD) of each set of

> **Class C 1:50,000**

**Version 1** 90 91.10% 100% 6.82 **Version 2** 91 90.50% 100% 6.85 **Version 4** 91 90.10% 100% 6.84 **TOPODATA** 92 83.30% 93.40% 10.38

From the results presented in table 2 one perceives that versions 1, 2 and 4 have very similar performances and present altimetric accuracy very near to the limits indicated for **class C of scale 1:50,000**. Only Topodata is indicated only for **class A of scale 1:100,000**. As the main objective of Topodata is to obtain a better detailing of the morphometric information derived from SRTM DEM, a small loss of accuracy is tolerated in favor to gain better detailing of the morphometric representation. Additionally, the goal and SD observed should be emphasized, mainly in versions 1, 2 and 4, showing that the DEM SRTM presents

**6.2. ASTER/VNIR: Planialtimetric assessment of the orthoimage and DEM** 

ASTER images (Advanced Spaceborn Emission and Reflection Radiometer), onboard Earth satellite, are very interesting for being of low-cost and providing good spectral resolution, besides allowing the generation of DEMs from the stereoscopic pair of the VNIR (Visible and Near Infrared) sensor. This sensor provides a spatial resolution of 15 m, counting with the green, red and near infrared bands (the latter being acquired with two different incidence angles in a same satellite passage). Due to these features, those images can be

Study area again was the vicinities of the municipality of São Sebastião. An assessment was carried out based on the results made from the images and DEMs generated according to

 With Orthoengine 10.2 by PCI Geomatics based on 2 scenes (same date) acquired September 19, 2008, with processing level L1A, making use of 12 control points and 9

**Class A 1:100,000**  **SD (m)** 

points used in the assessment for each DEM SRTM version.

**Table 2.** Summary of assessments of the 4 versions of DEM SRTM

**Assessment Points** 

The orthoimages and DEMs generated for assessment had the same resolution as raw data: 15 m, despite having carried out tests of the DEM with pixels resampled up to 60 m, without perceiving significant difference.

There was no disagreement between the results obtained for planimetry, placing the VNIR orthoimages in **class A for 1:50,000 scale**, with 92.7% of the 41 assessment points presenting errors of up to 40 m, with a standard deviation of 11.6 m.

In the case of altimetry, however, results were different depending on the approach used in DEM generation. Using Orthoengine, the worst results were obtained, since DEM meets the specifications for **class A for 1:100,00 scale**, with 94.2% of the assessment points presenting errors of up to 25 m, with a standard deviation of 10.5 m. When using the **ENVI /ASTERDTM,** with the same scenes, processing level and same 12 control points, the result changes to a **class C for 1:50,000 scale**, with 92.7% of the assessment points presenting errors of up to 15 m, with standard deviation of 8.6 m. Using the scenes with processing level L1B with **ENVI /ASTERDTM,** without any ground control point, the specification for a **class C for 1:50,000 scale** is reached, with 96.3% of the 41 assessment points presenting errors of up to 15 m, with a standard deviation of 6.1 m.

These results ensued a questioning to the PCI representative in Brazil, with forwarding of all the data used, being answered by PCI that there was no failure or problem. It is therefore understood that the ASTERDTM modeling - which is a specialized ASTER module - is more appropriate.

#### **6.3. ALOS/AVNIR-2: Planimetric assessment of orthoimage**

The ALOS/AVNIR-2 data, as well as those of the PRISM sensor of the same satellite, are of great interest for Brazil, since its data was distributed by IBGE (*Instituto Brasileiro de Geografia e Estatística*) for noncommercial users at a much lower price than those practiced by the market for products with the same features. It remained to know its accuracy in order to be able to fully explore its real capacity. The AVNIR-2 sensor acquired data in 4 spectral bands (blue, green, red and near infrared) with a spatial resolution of 10 m. Since the satellite contained a very advanced set of orbital and altitude control systems, its use would be very appropriate both for reference as for thematic cartography.

The results presented here refer to the work published by a group of IBGE employees in [19] who assessed the orthoimage geometry of this sensor.

Orthoimage was generated in Orthoengine 10.2, by PCI, with a resolution of 10 m, based on a scene acquired with processing level 1B2R, making use of seven ground control points and DEM SRTM version 4.0. The control points and the 34 assessment points were obtained from orthoimages in scale 1:25,000 generated by IBGE from photos in the scale 1:35,000. This

study area covered the cities of Uberlândia, Indianópolis and Araguari, state of Minas Gerais, in Southeast Brazil. The topography of this area is less mountainous with height differences not exceeding 400 m.

Contribution of New Sensors to Cartography 193

good geometry and it was habitual to use the panchromatic band of that sensor (HRVIR) in

The orthorectification of the panchromatic band (in fact it covers the red band – 0.61 to 0.68µm), with a 10 m spatial resolution, was carried out with Orthoengine 9.0, by PCI

The assessment used 7 points, whose coordinates were determined by relative static

The study area was also the same used in the assessment of the Landsat Orthoimage and corresponds to part of the municipality of Angra dos Reis, Rio de Janeiro, Southeast Brazil. The results **suggest** that the Orthoimage presents an accuracy compatible with the **Class A for 1:50,000 scale** or **Class C for 1:25.000 scale**, since all points presented errors up to 20.5 m and SD of 7.4 metros. Likewise as in the Landsat assessment, the use of a small amount of points in the assessment does not allow to surely warrant the accuracy, but it is an indicator

Finalizing this part of the chapter, we present a summary table (table 3) with results from the accuracy assessments in terms of geometry for each of the sensor products

**Sensor Product Scale Classe/PEC** 

**Geoeye-1** Orthoimage 1:2.000 Class B

**IKONOS-2** Orthoimage 1:2.000 Class C

**CARTOSAT-1** Orthoimage 1:10.000 Class B

**ALOS / PRISM** Orthoimage 1:25.000 Class A

**ALOS / AVNIR** Orthoimage 1:50.000 Class A **ASTER / VNIR** Orthoimage 1:50.000 Class B

**SPOT 4 / HRVIR: Pan** Orthoimage 1:50.000 Class A

**Landsat 7 / ETM+ / Multiespectral Band** Orthoimage 1:100.000 Class B

Orthophoto 1:2.000 Class A MDT 1:2.000 Class B MDS 1:5.000 Class C

DEM 1:10.000 Class C

DEM 1:10.000 Class C

DEM 1:25.000 Class A

DEM 1:25.000 Class A

DEM 1:50.000 Class C

Version 1 1:50.000 Class C Version 2 1:50.000 Class C Version 4 1:50.000 Class C Topodata 1:100.000 Class A

positioning (likewise as for the GCPs), with single frequency GNSS trackers.

scales 1:25.000 and 1:50.000.

Geomatics, using 7 GCPs and SRTM DEM.

of its quality in terms of geometry.

**LIDAR** 

**SRTM (DEM)** 

**Table 3.** Summary results of the assessments

analyzed:

The results indicate that the orthoimage presents a planimetric accuracy equivalent to the **class A of scale 1:50,000**, since 90% of the assessment points presented errors of up to 21.7 m (already including the external error of the orthophotos - of up to 12.5 m), with standard deviation of 3 m. The authors of the referred work emphasize that the assessment only focused on geometry, like the remaining assessments here presented.

#### **6.4. Landsat 7 ETM+: Planimetric assessment of the orthoimage**

This assessment was the first research on the geometric accuracy of remote sensors carried out in 2004, by Laboratory ESPAÇO, with the specific purpose to obtain the planimetric accuracy of the Landsat images when orthorectified using the SRTM DEM (a novelty at that time). Despite being a quite well-known sensor, we consider its inclusion in this chapter appropriate for historical reasons and for its resemblance with the TM images from Landsat 5. Presently (2012) Brazil is concluding the updating of reference maps in the scale 1:250,000 using TM sensor images as main input.

Orthoimage was produced from the band 3 (red) of a scene (Path/Row 218/076) of sensor ETM+ (Enhanced Thematic Mapper Plus), Landsat 7 satellite, acquired in August 1999, with processing level 1G. Orthorectification was made with Orthoengine 9.0, by PCI Geomatics, using 10 ground control points (GCPs) - whose coordinates were determined by a navigation GPS (C/A - Coarse Acquisition Code) - and SRTM DEM version 1 (90 m pixel). The choice for the navigation GPS was due to the ETM plus image characteristics - 30 m pixel - and the lack of availability of single or double frequency trackers at that time.

In the planimetric accuracy assessment of orthoimage from Landsat 7 ETM+ only 4 assessment points were used, with coordinates determined by relative static positioning, through single frequency GNSS receivers. It was chosen to work with a small number of points for the assessment, but to determine their coordinates with greater accuracy.

The study area corresponds to the part of the municipality of Angra dos Reis, in Rio de Janeiro, Southeast Brazil. Relief is mountainous in most of the scene, with height differences over 1,000 m, for being part of the Serra do Mar Range. The prevailing vegetable cover consists of tropical forests, with presence of grasses/pastures in some areas.

It was observed that the 4 assessment points presented positioning errors of up to 70 m with an SD of 13 m. The results obtained suggest that the orthoimage presents a planimetric accuracy compatible with the specification for a **class B for 1:100,00 scale**.

#### **6.5. SPOT 4: Planimetric assessment of the orthoimage**

Likewise as in the assessment of the Landsat Orthoimage, this was one of our first planimetric accuracy assessments. The SPOT 4 images were renowned as having a very good geometry and it was habitual to use the panchromatic band of that sensor (HRVIR) in scales 1:25.000 and 1:50.000.

The orthorectification of the panchromatic band (in fact it covers the red band – 0.61 to 0.68µm), with a 10 m spatial resolution, was carried out with Orthoengine 9.0, by PCI Geomatics, using 7 GCPs and SRTM DEM.

The assessment used 7 points, whose coordinates were determined by relative static positioning (likewise as for the GCPs), with single frequency GNSS trackers.

The study area was also the same used in the assessment of the Landsat Orthoimage and corresponds to part of the municipality of Angra dos Reis, Rio de Janeiro, Southeast Brazil.

The results **suggest** that the Orthoimage presents an accuracy compatible with the **Class A for 1:50,000 scale** or **Class C for 1:25.000 scale**, since all points presented errors up to 20.5 m and SD of 7.4 metros. Likewise as in the Landsat assessment, the use of a small amount of points in the assessment does not allow to surely warrant the accuracy, but it is an indicator of its quality in terms of geometry.

Finalizing this part of the chapter, we present a summary table (table 3) with results from the accuracy assessments in terms of geometry for each of the sensor products analyzed:


**Table 3.** Summary results of the assessments

192 Cartography – A Tool for Spatial Analysis

differences not exceeding 400 m.

using TM sensor images as main input.

study area covered the cities of Uberlândia, Indianópolis and Araguari, state of Minas Gerais, in Southeast Brazil. The topography of this area is less mountainous with height

The results indicate that the orthoimage presents a planimetric accuracy equivalent to the **class A of scale 1:50,000**, since 90% of the assessment points presented errors of up to 21.7 m (already including the external error of the orthophotos - of up to 12.5 m), with standard deviation of 3 m. The authors of the referred work emphasize that the assessment only

This assessment was the first research on the geometric accuracy of remote sensors carried out in 2004, by Laboratory ESPAÇO, with the specific purpose to obtain the planimetric accuracy of the Landsat images when orthorectified using the SRTM DEM (a novelty at that time). Despite being a quite well-known sensor, we consider its inclusion in this chapter appropriate for historical reasons and for its resemblance with the TM images from Landsat 5. Presently (2012) Brazil is concluding the updating of reference maps in the scale 1:250,000

Orthoimage was produced from the band 3 (red) of a scene (Path/Row 218/076) of sensor ETM+ (Enhanced Thematic Mapper Plus), Landsat 7 satellite, acquired in August 1999, with processing level 1G. Orthorectification was made with Orthoengine 9.0, by PCI Geomatics, using 10 ground control points (GCPs) - whose coordinates were determined by a navigation GPS (C/A - Coarse Acquisition Code) - and SRTM DEM version 1 (90 m pixel). The choice for the navigation GPS was due to the ETM plus image characteristics - 30 m

In the planimetric accuracy assessment of orthoimage from Landsat 7 ETM+ only 4 assessment points were used, with coordinates determined by relative static positioning, through single frequency GNSS receivers. It was chosen to work with a small number of

The study area corresponds to the part of the municipality of Angra dos Reis, in Rio de Janeiro, Southeast Brazil. Relief is mountainous in most of the scene, with height differences over 1,000 m, for being part of the Serra do Mar Range. The prevailing vegetable cover

It was observed that the 4 assessment points presented positioning errors of up to 70 m with an SD of 13 m. The results obtained suggest that the orthoimage presents a planimetric

Likewise as in the assessment of the Landsat Orthoimage, this was one of our first planimetric accuracy assessments. The SPOT 4 images were renowned as having a very

pixel - and the lack of availability of single or double frequency trackers at that time.

points for the assessment, but to determine their coordinates with greater accuracy.

consists of tropical forests, with presence of grasses/pastures in some areas.

accuracy compatible with the specification for a **class B for 1:100,00 scale**.

**6.5. SPOT 4: Planimetric assessment of the orthoimage** 

focused on geometry, like the remaining assessments here presented.

**6.4. Landsat 7 ETM+: Planimetric assessment of the orthoimage** 
