technical specifications - geomatics · s technical specifications 3 beginner – module 1a...

Technical Specifications

1

s Technical Specifications

2

Beginner – Module 1A

Contents

INTRODUCTION ............................................................................................................3

ABOUT THIS LAB ..........................................................................................................3

IMPORTANCE OF THE MODULE ....................................................................................3

VIEWING LAYERS..........................................................................................................4

Opening an image file in Focus ..........................................................................................4

Changing the band combination for an RGB Layer ...........................................................5

...........................................................................................................................................6

Loading a grayscale layer using the Add Layer Wizard .....................................................6

Loading a pseudocolor image from the Files tree .............................................................6

USING THE ZOOM WINDOW ........................................................................................7

MEASURE TOOLS..........................................................................................................8

Measuring distances and area ..........................................................................................8

TOPICS LEARNED ........................................................................................................ 10

FURTHER READINGS ................................................................................................... 10

REFERENCES ............................................................................................................... 10


3


Introduction Welcome to the Visualizing Image Data module, an introductory lab using

Geomatica’s Focus technology. This course lab is written for beginner users of

the geospatial software. In this lab you will master the basics needed to

visualize raster and vector datasets. This manual contains three modules. Each

module contains lessons that are built on basic tasks that you are likely to

perform in your daily work. They provide instruction for using the software to

carry out essential processes in Geomatica Focus.

About this Lab The following modules will be covered in this lab:

Viewing Layers

Using the Zoom Tools

Measure Tools Each module in this course lab contains a series of hands-on lessons that let you work with the software and a set of sample data. Lessons have brief introductions followed by tasks and procedures in numbered steps. In addition, on the left panel, remote sensing theory in red font color and software tips in black font color can be found.

Importance of the Module Remote Sensing is the art and science of obtaining information about an area

of object through the analysis obtained by a device that is not in contact1. The

visualization of earth surface features by relative response of spectral

signatures in the remotely sensed satellite data is critical for analysis. This

module teaches the user how to use a variety of Geomatica tools in order to

visualize remote sensing data.


4


Viewing Layers

Opening an image file in Focus

1. Open Focus from the Start Menu

2. From the Focus File menu, click Open. A File Selection window opens (Note 1).

3. In the Geomatica program folder, locate and open the GEO Data folder.

4. Click toronto_l7.pix (Note 2 and 3).

5. Click open (Note 4)

Figure 1. Focus Window

6. Click in the Focus view area (Note 5)

Figure 2. DN values

Color Composite Images

Multispectral sensors acquire data

from different portions of the electromagnetic spectrum, which is stored in channels, or bands. A color composite is created by displaying three different bands of data using the red, green and blue (RGB) color guns or display channels. The DN (digital number) of each pixel in each channel represents a brightness value for the RGB components of the color composite. Color composites are important for effective visual interpretation of multispectral imagery. The order in which channels are placed in the color composite depends on which feature(s) you want to enhance in the image. For example, in a 4, 3, 2 Landsat 7 false color composite, healthy vegetation will be red and urban areas will be cyan, making the distinction between these two classes quite clear.

Note 1. It is now possible to open

imagery in Focus by dragging and dropping directly from the Microsoft Windows Explorer panel to the Focus view canvas. If the file you open has fewer than three raster layers, the first layer is displayed as a single grayscale layer. If it does not have raster data, the first vector layer is displayed.

Note 2. If metadata is present, Focus will use the metadata to determine which channels are added to the RGB display channels. Alternatively, you can set the default RGB order in the Tools | Options window.

Note 3. By default, the first three

image channels of the toronto_l7.pix file are automatically loaded as a color composite in the Focus view area and an RGB Layer is listed in the Maps tree.

Note 4. Focus lets you map channels of data to different display channels to view different band combinations. The RGB Mapping window lets you change or map the channel data to a color display channel and show the changes in the view area.

Note 5. The cursor moves to this position in the image. The DN values of the red, green, and blue layers for the pixel identified by the cursor position are displayed on the status

bar.


5


Changing the band combination for an RGB Layer

1. From the Layer menu, select RGB Mapper. The RGB Mapper opens.

Figure 3. RGB Mapper

2. In the RGB Mapper window, click in the columns to display Band 1

in Blue, Band 2 in Green and Band 3 in Red.

3. Click Close (Note 1). A true color composite is displayed in the Focus view area

Figure 4. Enhancements Button

4. Re-apply an image enhancement to the true color composite.

Note 1. Changing band combinations

cancels enhancements you have

applied. To maintain an enhancement,

you must enhance the image again.

True Color Composite: the layers are sensitive to blue, green, and red light - the same as our eyes1.

False Color Composite: targets with

high near-infrared reflectance appear red, those with a high red reflectance appear green, and those with a high green reflectance appear blue, thus giving us a "false" presentation of the targets relative to the colour we normally perceive them to be.


6


Loading a grayscale layer using the Add Layer Wizard

1. From the Layer menu, select Add. The Add Layer Wizard opens.

Figure 5. Add Layer Wizard

2. From the list of layer types to add, select Grayscale.

3. Click Next. The next step of the Add Layer Wizard is displayed.

4. Click Browse.

5. From the GEO Data folder, select the toronto_spot.pix file.

6. Click Open. The toronto_spot.pix file appears in the list of available files. One channel is shown in the available channels list.

7. From the available channels list, select the Panchromatic Band.

8. Click Finish.

The Add Layer wizard closes and the grayscale image is displayed on top of the RGB layer in the Focus view area. A grayscale layer is listed in the Maps tree.

Loading a pseudocolor image from the Files tree

1. Expand the list of rasters in the toronto_dem.pix file.

2. Right-click the DEM channel (Note 1)

From the shortcut menu, select View As Pseudocolor. The DEM is displayed in Focus as a pseudocolor layer

Grayscale images: Panchromatic

sensors collect data in a broad region of the electromagnetic spectrum and store this data in one channel, or band. Multispectral sensors detect energy from specific wavelength ranges and store this information in several channels. In either case, when viewing a single channel, it is visualized as a grayscale image. For grayscale images, the computer displays each digital number (DN) as a different brightness level of gray.

Pseudocolor: Single channels can be visualized with color by assigning a psuedo-color table (PCT) to a grayscale image. In a psuedo-color image, each DN is assigned a red, green and blue (RGB) value. Often, more information can be visually extracted from a PCT image compared to a grayscale image. This is because in general, the human eye can only detect 16-32 shades of

gray, but can distinguish between roughly 2 000 000 colors.

When a file is loaded into Focus, a

default layer is displayed in the view area and is listed in the Maps tree. You can also add files to the Files tree and load specific layers in different ways.

Note 1. You can also load grayscale

layers and RGB layers from the Files

Tree. For an RGB layer, use your CTRL

key to select three channels. The order

you select your channels is the order

they will be displayed as RGB.


7


Figure 6 .Pseudocolor image displayed in Focus

Using the Zoom window

To open and use the Zoom window

1. From the View menu, select Zoom window (Note 1). The Zoom window opens.

Figure 7. Zoom window

Note 1. The zoom window lets you see a

linked copy of your image data in a

separate viewer. You can zoom the

images independently, using one image to

locate features and the other to zoom

them for a closer look.

Spatial resolution of the sensor and

refers to the size of the smallest possible

feature that can be detected.

Instantaneous Field of View (IFOV) is the

angular cone of visibility of the sensor.

Resolution cell is the size of the area

viewed and determines a sensor's

maximum spatial resolution


8


2. In the upper-left corner of the zoom window, click the Lock Window Position button.

3. Click in the Focus view area. The cursors in both windows are linked, but the image in the Zoom Window does not change.

4. To unlock the Zoom Window, click the Lock Window Position button again.

Measure Tools

Measuring distances and area

You can measure features in the Focus view area using the Measure tool. Select either the Line, Polygon, Rectangle or Ellipse tool to compute measurements of distance and area.

To use the Measure tool

1. On the toolbar, click the Measure arrow and select Polygon. The Polygon measurement tool is now active.

Figure 8. Measure Tool in Focus

Note 1. You are able to specify the units

of measure by selecting the arrow beside

the measurement tool and choosing the

appropriate units from the Linear Units,

Area Units, or Angle Units menus.

Note 1. You are able to specify the units

of measure by selecting the arrow beside

the measurement tool and choosing the

appropriate units from the Linear Units,

Area Units, or Angle Units menus.

Scale is the scale represents the

relationship of the distance on the

map/data to the actual distance on the

ground.


9


2. Using the zoom tools, zoom to Lester B. Pearson International

Airport. The image zooms to show the selected region.

3.

4.

5.

6.

7.

Figure 9. Zoom Tool in Focus

3. Roughly outline the airport area using the Polygon measurement tool. Measurements for the area are displayed

on the status bar (Note 1). Experiment with the other measurement tools available in Focus.


10


Topics Learned

Further Readings • What is Remote Sensing?

• Elements of Visual Interpretation

• The Electromagnetic Spectrum

References • Lillesand, T.M. and Kiefer, R.W. (1994) Remote Sensing and

Image Interpretation. John Wiley and Sons Inc., New York.

Remote Sensing Theory • Satellite Imagery band • Band Combination

Geomatica: • Open different types of layers • Use Map View Mode and Area View

Mode • Manage layer properties • View file properties • Use the Overview and Zoom

Windows • Use the Zoom and Pan Tools

• Measure the size of a feature

http://www.nrcan.gc.ca/earth-sciences/geomatics/satellite-imagery-air-photos/satellite-imagery-products/educational-resources/9363



technical specifications - geomatics · s technical specifications 3 beginner – module 1a...

Documents