GIS Chapter 1: Raster Data Model

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Questions and Answers

What is the approximate spatial resolution of Sentinel-1 SAR images?

The approximate spatial resolution of Sentinel-1 SAR images is 20 meters.

In what year was Sentinel-2 launched and how many bands does it gather data with?

Sentinel-2 was launched in 2015 and gathers data with 13 bands.

What primary mission does Sentinel-3 serve?

Ocean monitoring and global sea level variations

List two satellites that offer SAR images alongside Sentinel-1.

TerraSAR-X and RADARSAT-2 are two satellites that offer SAR images alongside Sentinel-1. Signup and view all the answers

How do the spatial resolutions of Sentinel-2 bands vary?

Sentinel-2 has four bands at 10 meters, six bands at 20 meters, and three bands at 60 meters. Signup and view all the answers

What is the primary reason a floating-point raster requires more memory than an integer raster?

A floating-point raster requires more memory due to its potentially large number of cell values, which necessitates additional storage. Signup and view all the answers

How does the value attribute table differ between integer and floating-point rasters?

An integer raster has a value attribute table for cell value access, whereas a floating-point raster typically does not due to its vast number of potential values. Signup and view all the answers

What must be used to query and display a floating-point raster instead of individual cell values?

Value ranges, such as 12.0 to 19.9, must be used to query and display a floating-point raster. Signup and view all the answers

Where does the cell value generally register within the cell for distance measurement operations?

The cell value typically applies to the center of the cell in operations involving distance measurements. Signup and view all the answers

What determines the spatial resolution of a raster?

The spatial resolution of a raster is determined by the cell size, which refers to the area represented by a single cell. Signup and view all the answers

If a raster has a cell size of 100 m², what is the length of each side of its cell?

Each side of a cell in a 100 m² raster is 10 meters in length. Signup and view all the answers

What do the terms 'cell-based' and 'point-based' refer to in raster data operations?

'Cell-based' refers to operations that assume the cell value applies to the entire cell, while 'point-based' relates to operations focusing on specific points within the raster. Signup and view all the answers

Why is the likelihood of finding a specific value in a floating-point raster considered low?

The likelihood is low because floating-point rasters can contain a vast array of values, making it difficult to pinpoint individual ones. Signup and view all the answers

What is the impact of having a larger raster cell size on spatial feature representation?

A larger raster cell size increases the chance of mixed features such as forest, pasture, and water being represented in a single cell. Signup and view all the answers

How does reducing raster cell size affect data processing requirements?

Reducing raster cell size increases the data volume and processing time required for analysis. Signup and view all the answers

Define cell depth in the context of raster data.

Cell depth refers to the number of bits used to store cell values in a raster, affecting the range of possible values. Signup and view all the answers

What is the difference in storage capacity between an 8-bit and a 16-bit raster?

An 8-bit raster can store 256 values, while a 16-bit raster can store 65,536 values. Signup and view all the answers

Explain the concept of raster bands in raster data.

Raster bands refer to the layers that may contain one or multiple values at each cell location, allowing for single-band or multiband data. Signup and view all the answers

Give an example of a single-band raster and a multiband raster.

An example of a single-band raster is an elevation raster, while a multiband raster example is a satellite image with multiple bands. Signup and view all the answers

What is the relationship between cell depth and data volume in raster models?

Higher cell depth increases the range of values that can be stored, leading to larger data volume for the raster model. Signup and view all the answers

Why might a GIS analyst choose a raster with a smaller cell size?

An analyst might choose a smaller cell size to achieve higher spatial resolution and better representation of features. Signup and view all the answers

What is the orbit height for the Sentinel-2 satellites?

786 km Signup and view all the answers

Which organization launched the Sentinel satellite series?

ESA Signup and view all the answers

What year was the Sentinel-1A satellite launched?

2014 Signup and view all the answers

What is the main purpose of NASA's Terra spacecraft?

To study interactions among the Earth's atmosphere, lands, oceans, life, and radiant energy. Signup and view all the answers

How many days is the repeat cycle for the Sentinel-1 satellites?

6 days Signup and view all the answers

What is unique about the ASTER instrument on the Terra satellite?

It is designed for high spatial resolution applications in land cover classification and change detection. Signup and view all the answers

What is the spatial resolution of ASTER in the visible and near-infrared range?

15 meters Signup and view all the answers

When is Sentinel-2C expected to be launched?

2024 Signup and view all the answers

What is the resolution of panchromatic images provided by SPOT 6 and SPOT 7?

The resolution of panchromatic images provided by SPOT 6 and SPOT 7 is 1.5 meters. Signup and view all the answers

In what year was SPOT 5 launched?

SPOT 5 was launched in 2002. Signup and view all the answers

Which organization is responsible for SPOT 6 and SPOT 7?

SPOT 6 and SPOT 7 are operated by Airbus Defence and Space. Signup and view all the answers

What is the orbit type for all SPOT satellites mentioned?

All SPOT satellites mentioned utilize a Sun Synchronous orbit. Signup and view all the answers

What is the repeat cycle for the SPOT satellites?

The repeat cycle for the SPOT satellites is 26 days. Signup and view all the answers

What was the launch year of the first SPOT satellite?

The first SPOT satellite was launched in 1986. Signup and view all the answers

What is the resolution of the multispectral images provided by SPOT 6 and SPOT 7?

The resolution of multispectral images provided by SPOT 6 and SPOT 7 is 6 meters. Signup and view all the answers

Which SPOT satellite was launched after SPOT 5?

SPOT 6 was launched after SPOT 5. Signup and view all the answers

Study Notes

Raster Data Models

Floating-point rasters require more memory than integer rasters, especially critical in large GIS projects.
Integer rasters include a value attribute table, allowing cell value access, whereas floating-point rasters typically do not due to numerous potential cell values.
Querying individual cell values in integer rasters is straightforward, while floating-point rasters require value ranges, reducing the likelihood of identifying a specific value.

Cell Value Registration

Cell value typically applies to the center of the cell for distance measurement operations.
Most raster operations are cell-based, assuming cell values cover the entire cell rather than just a point.

Cell Size

The size of an area represented by a single raster cell affects spatial resolution; a 10-meter raster has finer resolution than a 30-meter raster.
Larger cell sizes increase the chances of mixed spatial features within a cell, which decreases with smaller cell sizes.
Smaller cell sizes result in larger data volumes and more processing time.

Cell Depth

Cell depth indicates the number of bits used for storing cell values.
An 8-bit raster can store 256 values (2^8), while a 16-bit raster can store 65,536 values (2^16).
Higher cell depth enables storage of a broader range of values, influencing data volume.

Raster Bands

Rasters can be single or multiband; single-band rasters have one cell value per location, such as elevation.
Multiband rasters, like satellite images, can provide multiple values at each cell, with various bands capturing different wavelengths.

Satellite Data Examples

SPOT 6 and SPOT 7 provide panchromatic images at 1.5-meter resolution and multispectral images at 6-meter resolution.
Various SPOT satellites, launched between 1986 and 2014, operate in sun-synchronous orbits at altitudes of approximately 694-832 km.
Sentinel satellites offer free data; Sentinel-1 focuses on C-band SAR images at roughly 20-meter resolution, while Sentinel-2 uses 13 bands across visible to infrared ranges with variable spatial resolutions.

Terra Satellite

Launched in 1999 by NASA, Terra monitors Earth's atmosphere, land, oceans, and energy interactions.
Carries instruments like ASTER (provides high spatial resolution at 15m in visible and near-infrared, 30m in shortwave infrared, and 90m in thermal infrared) and MODIS for various Earth observation applications.

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Description

This quiz covers the fundamentals of raster data models and digital elevation models as introduced in Chapter 1 of 'Introduction to Geographic Information Systems' by Kang-tsung Chang. Understand the applications of these concepts in civil engineering and GIS. Test your knowledge on key principles and their practical applications.