Geospatial Data Collection: Remote Sensing & Ground Methods

What are the two primary methods for collecting geospatial data?

On-the-ground measurements (surveying and GPS/GNSS) and remote sensing.

What is the main advantage of on-the-ground data collection methods?

They generate very accurate and precise geospatial data.

What is a limitation of on-the-ground data collection methods?

They can only cover small areas at a time.

What is remote sensing?

The collection of data using methods that do not directly interact with the physical environment, typically from above ground.

What is the accuracy of modern surveying technology?

99.8% accuracy, precise to 1/100 of an inch.

How does GPS determine the location of a receiver?

By using trilateration from signals received from multiple satellites.

What does GNSS stand for?

Global Navigation Satellite Systems.

Name one satellite system included in GNSS.

Global Positioning System (GPS), GLONASS, BeiDou, Galileo, QZSS, or IRNSS.

What is the role of real-time kinematics (RTK) in GNSS?

It improves trilateration accuracy by using signals from multiple satellite systems.

What is the definition of remote sensing according to Campbell & Wynne (2011)?

The practice of deriving information about the Earth's land and water surfaces using images acquired from an overhead perspective.

What was the earliest method of remote sensing?

Taking photographs from the air using balloons, airplanes, or pigeons.

What is the resolution of Landsat 1 compared to Landsat 9?

Landsat 1 had 80 meters resolution, while Landsat 9 has up to 15 meters resolution.

What are the three components of vector data models?

Points, lines, and polygons.

What do points represent in vector data models?

Locations with no dimensions (no length, width, area).

What type of features do lines represent in vector data models?

Linear features such as roads and rivers.

What do polygons represent in vector data models?

Features that have an area, such as city boundaries or lakes.

How does the scale of a map affect the representation of features?

Points, lines, and polygons may represent different features depending on the scale.

What are unmanned aerial vehicles (UAVs) used for in remote sensing?

They are equipped with sensors to collect high-resolution data from closer to the ground.

What is a limitation of drones compared to satellites in remote sensing?

Drones can only cover relatively small areas.

In what contexts are drones used for remote sensing?

Agriculture, military, emergency management, and conservation.

What is the significance of selective availability in GPS technology?

It initially limited GPS access to military applications but was later removed for commercial use.

What is the purpose of data models in GIS?

To convert geographical features into graphical features on a map.

What is the difference between vector and raster data models?

Vector data models use points, lines, and polygons, while raster data models use grid cells to represent data.

What is the importance of the electromagnetic spectrum in remote sensing?

It is used to acquire data about the Earth's surface through reflected or emitted radiation.

What is the role of satellite sensors in Landsat satellites?

They record multiple spectral bands or wavelengths of light to capture different aspects of the landscape.

What was significant about Waldseemüller's map in 1507?

It was the first to identify a western land with the Pacific Ocean on its west side, naming it 'America' after Amerigo Vespucci.

What are ESRI Basemaps?

They include useful vector-based maps for geographic features.

How are geographic features represented on US Topo maps?

Points, lines, and polygons are used to define geographic features.

What does the elevation of Cerro La Jara represent on the map?

Cerro La Jara has an elevation of 8745 feet.

What do lines represent on a topographical map?

Lines represent features such as roads and rivers.

What are attributes in the context of GIS?

Attributes are characteristics recorded for each point, line, or polygon.

What is an attribute table?

A tabular file or database that contains information about features on a map.

What does the Shape field in an attribute table indicate?

It indicates that the data are recorded as points.

What types of data can fields in an attribute table represent?

Fields can represent string/text data, integer data, real numbers, dates, and logical values.

How is line data more complex than point data?

Line data includes starting and ending points, length, and direction.

What is the significance of address numbers on streets?

Address numbers increase or decrease depending on the direction of travel.

What is a raster data model?

A cell-based data model that divides an image into small cells, similar to pixels.

What does ground sample distance (GSD) refer to?

GSD refers to the size of each cell in a raster image, indicating the area it represents.

How does the size of raster cells affect resolution?

Larger cells result in lower resolution and accuracy, while smaller cells provide higher resolution and accuracy.

What happens when a vector map is converted to a raster image?

A grid pattern is overlaid, filling cells based on the presence of features.

What types of data can be recorded in raster cells?

Raster cells can record categorical data (e.g., vegetation type) or numerical data (e.g., average elevation).

What formats can raster data be represented in?

Formats include Geodatabase rasters, TIFF, Esri Grid files, CRF raster files, ERDAS IMAGINE files, and JPEG files.

What is the relationship between cell size and file size in raster data?

Smaller cell sizes lead to larger file sizes due to increased detail.

What is the role of attributes in Google Maps?

Attributes provide details like address, phone number, and customer rating for locations.

What does the term 'spatial resolution' refer to?

Spatial resolution refers to how closely a raster image represents the real world based on cell size.

How does processing speed relate to raster cell size?

Larger cells allow for faster processing, while smaller cells slow down processing due to increased detail.

What does the term 'feature spatial accuracy' mean?

It refers to how accurately a raster image represents real-world features.

What is the significance of the number of cells in a raster image?

The number of cells increases as cell size decreases, improving detail and accuracy.

What is a blue polygon used to represent on a map?

It represents a small lake on La Jara Creek.

What is the purpose of using a grid pattern in raster data?

To overlay a raster image and approximate the shape of original vector features.

What are the two sides of a street segment represented in an attribute table?

Addresses on the left and right sides of the street segment.

What does the term 'presence or absence of a feature' refer to in raster data?

It indicates whether a feature is represented in a specific cell of the raster image.

How does raster data differ from vector data?

Raster data is continuous and cell-based, while vector data is discrete and uses points, lines, and polygons.