Geospatial Techniques

What is geoinformatics?

A framework to capture, process and display spatial data

What components are involved in geoinformatics?

Cartography and geodesy

What is geodesy?

The measurement of the size and shape of the Earth

How did Eratosthenes estimate the Earth's circumference?

By using the assumption that the sun's rays are parallel

What is the current estimate for the Earth's circumference?

24,855 miles

How can the curvature of the Earth be measured?

By measuring the distance between two reference points

What is a coordinate system?

A reference system used to represent the locations of geographic features

What are the two common types of coordinate systems for geospatial data?

Latitude and longitude

What is a spheroid?

The shape of the Earth

What is the difference between a spheroid and an ellipsoid?

A spheroid is circular around the middle, while an ellipsoid is not necessarily circular around the middle.

What does GNSS stand for?

Global Navigation Satellite Systems

What is the difference between GPS and GNSS?

GPS is a specific PNT service owned and operated by the United States military, while GNSS is a generic term that encompasses other similar systems owned and operated by other countries and organizations.

What does PNT stand for?

Position, Navigation and Timing

When was GPS first launched?

GPS was first launched in 1973

When did GPS become fully operational?

GPS became fully operational in 1995

What is the purpose of the space segment in the GPS system?

The space segment of the GPS system consists of at least 24 satellites that provide improved accuracy, signal strength, and quality.

How long is the design lifespan of the GPS satellites?

The design lifespan of the GPS satellites is 12 years.

What is the purpose of the control segment in the GPS system?

The control segment of the GPS system provides command and control of the GPS constellation, computes the precise locations of the satellites, generates navigation messages for upload to the satellites, monitors satellite broadcasts and system integrity to ensure constellation health and accuracy, and performs satellite maintenance and anomaly resolution.

What is the purpose of the user segment in the GPS system?

The user segment of the GPS system consists of GPS receivers that measure distance using the travel time of radio signals and correct for any delays the signal experiences as it travels through the atmosphere.

What is the purpose of the monitor stations in the GPS system?

The monitor stations in the GPS system track GPS satellites as they pass overhead, collect navigation signals, range/carrier measurements, and atmospheric data, and feed observations to the master control station.

What is the purpose of the master control station in the GPS system?

The master control station in the GPS system provides command and control of the GPS constellation, computes the precise locations of the satellites, generates navigation messages for upload to the satellites, monitors satellite broadcasts and system integrity to ensure constellation health and accuracy, and performs satellite maintenance and anomaly resolution.

What is the purpose of the ground antennas in the GPS system?

The ground antennas in the GPS system send commands, navigation data uploads, and processor program loads to the satellites, collect telemetry, communicate via S-band and perform S-band ranging to provide anomaly resolution and early orbit support.

What is trilateration?

Trilateration is the process of determining the relative positions of objects using the geometry of triangles, based on distances (not angles).

How does GPS measure time?

GPS measures time by comparing the offset of the satellite's pseudo-random code compared to the receiver. The difference between the two is the travel time of the signal, which, when multiplied by the speed of light, gives the distance.

What is Dilution of Precision (DOP)?

Dilution of Precision (DOP) is a measure of the quality of the geometry of the satellites in view, which affects the accuracy of the GPS measurement. There are different types of DOP, such as Horizontal Dilution of Precision (HDOP), Vertical Dilution of Precision (VDOP), and Position Dilution of Precision (PDOP).

Who owns GPS

US

What are the 3 segments of a GNSS system and what are those segments for?

1. space segment



→ 2 Control segment



→ 3 User segment

When was GPS available for Civilian use

1980s

space segment

* Advance atomic clocks
* improved accuracy, signal strength and quality
* 12- year design lifespan
* launched in 2010-2016
* at least 24 satellites
* currently 31

Sources of error (high to low)

1. timing (clock in source)
2. upper atmosphere (ionosphere)
3. timing (receiver)
4. satellite orbit
5. lower atmosphere: (troposphere, tropopause and stratosphere
6. multipath

GLONASS

GLONASS (Globalnaya Navigazionnaya Sputnikovaya Sistema, or Global Navigation Satellite System) Operated by the Russian Federation. The fully operational system consists of 24+ satellites

What is remote sensing

Remote sensing is the science and art of obtaining information about an object, area, or phenomenon through the analysis of data acquired by a device not in contact with the object, area, or phenomenon under investigation.

Who coined the term remote sensing and when

The term was first used in the United States in the 1950s by Ms. Evelyn Pruitt of the U.S. Office of Naval Research.

What is the process involved in remote sensing

The process involves the detection and measurement of radiation of different wavelengths reflected or emitted from distant objects or materials, by which they may be identified and categorized by class/type, substance, and spatial distribution.

who took the first picture of nature and when

Niepce took the first picture of nature in 1827, which required an 8-hour exposure.

Who announced competing photographic discoveries in 1839, and what were their discoveries?

Louis Daguerre in France and William Henry Fox Talbot in England announced competing photographic discoveries in 1839. Daguerre exposed an image on a silver-plated copper plate, while Talbot produced a negative image on paper from which multiple positive images could be printed.

Who took the first aerial photograph, and when was it taken?

Gasper Felix Tournachon "Nadar" took the first aerial photograph from a captive balloon from an altitude of 1,200 feet over Paris in 1858.

When were the first space photographs taken, and how were they taken?

The first space photographs were taken in 1946 from V-2 rockets during World War II.

When was the U-2 first flown, and what was its significance?

The U-2 was first flown in 1954 and was significant because it enabled the United States to obtain aerial photographs of the Soviet Union during the Cold War.

When was Sputnik-1 launched, and what was its significance?

Sputnik-1 was launched in 1957 by Russia and was the first artificial satellite, marking the start of the Space Age.

When was TIROS-1 launched, and what was its significance?

TIROS-1 was launched in 1960 and was the first meteorological satellite.

What were the CORONA satellites used for?

CORONA satellites were used for photographic surveillance of the Soviet Union (USSR) and the People's Republic of China from June 1959 to May 1972.

When was WorldView-4 launched, and what are its features?

WorldView-4 was launched in November 2016 and has an altitude of 617 kilometers, 31 cm panchromatic resolution, 1.24 m multispectral resolution, and 4 m CE90 accuracy at nadir.

When was Landsat 9 launched, and what are its features?

Landsat 9 was launched in 2021 and has an Operational Land Imager 2 (OLI-2) that measures the visible, near infrared, and shortwave infrared portions of the electromagnetic spectrum. Its spatial resolution is 15 m for the panchromatic band and 30 m for the multispectral bands. The Thermal Infrared Sensor 2 (TIRS-2) measures land surface temperature in two thermal infrared bands.

What are the two broad types of remote sensing?

The two broad types of remote sensing are passive and active instruments. Passive instruments detect natural energy that is reflected or emitted from the observed scene, while active instruments provide their own energy (electromagnetic radiation) to illuminate the object or scene they observe.

Band 1

senses deep blues and violets. Uses include imaging shallow water, and tracking fine particles like dust and smoke. Difficult to image

Band 2, 3 and 4

visible blue, green and red

Band 5

Near-infrared (NIR) - Good for vegetation

Band 6 and 7

cover different slices of the shortwaves infrared (SWR). Useful for telling wet earth from dry earth, and for geology: rocks and soils that look similar in other bands often have strong contrasts in SWIR

Band 8

Panchromatic or ‘pan’ band. just like black and white film: combines visible colours into one channel. Sharpest of all the bands, with a resolution of 15 meters (50 feet)

Band 9

covers a very thin slice of wavelengths: only 1370 + 10 nanometers. Is just for clouds.

Band 10 and 11

thermal infrared, or TIR (heat). Not temperature of the air, but the ground itself, which is often much hotter than the air. Very dark cold spots match the clouds in Band 9. After them, irrigated vegetation is coolest, followed by open water and natural vegetation.

Electronic

Isolated atoms and ions have discrete energy states. Absorption of photons of a specific wavelength causes a change from one energy state to a higher one. Emission of a photon occurs as a result of a change in an energy state to a lower one. When a photon is absorbed it is usually not emitted at the same wavelength.

Vibrational

The bonds in a molecule or crystal lattice are like springs with attached weights: the whole system can vibrate. The frequency of vibration depends on the strength of each spring (the bond in a molecule) and their masses (the mass of each element in a molecule).

Aeromag

* Reds show magnetic highs and blues show magnetic lows.
* The magnetic anomaly map is useful for showing variations, both local and regional, within the subsurface.
* Linear features, clearly seen on shaded relief images as black shadows, are seen where magnetic gradients occur, for example along dykes or faults zone.

What is the GOCE mission, and when was it launched?

The GOCE (Gravity field and steady-state Ocean Circulation Explorer) mission is an Earth Explorer mission that was launched on 17/03/2009 by ESA.

What was the SMOS mission designed for, and when was it launched?

The SMOS mission was designed to measure soil moisture and ocean salinity and was launched on 02/07/2009.

What was the mission duration of the CryoSat mission, and when was it launched?

The CryoSat mission was launched on 08/04/2010, and its mission duration was 6 months commissioning (April 2010 to November 2010) plus a 3-year nominal mission. The mission was later extended until December 2019.

What is the objective of the Swarm mission?

The Swarm mission is designed to offer a unique view inside the Earth to study core dynamics, geodynamo processes, and core-mantle interactions, among other things.

What are the Swarm sensors?

The Swarm sensors include Vector Field Magnetometer, Absolute Scalar Magnetometer, Accelerometer, Electrical Field Instrument, GPS Receiver, and Laser Retroreflector.

What is Copernicus, and what are its objectives?

Copernicus is an EU program designed to improve the management of the environment, understand and mitigate the effects of climate change, and ensure civil security.

What is the objective of the Sentinel-1A and -1B mission?

The objective of the Sentinel-1A and -1B mission is to provide all-weather, day-and-night imagery of the Earth's surface.

What is the objective of the Sentinel-2 mission?

The objective of the Sentinel-2 mission is to provide multispectral imagery of the Earth's surface, with a swath width of 290 km and spatial resolutions of 10 m.

What is the objective of the Sentinel-3 mission?

The objective of the Sentinel-3 mission is to measure the Earth's oceans, land, ice, and atmosphere to understand large-scale global dynamics.

What is the objective of the Sentinel-4 mission?

The objective of the Sentinel-4 mission is to monitor key air quality trace gases and aerosols over Europe using a passive imaging spectrometer.

What is the objective of the Sentinel-5P mission?

The objective of the Sentinel-5P mission is to perform atmospheric measurements with high spatiotemporal resolution for air quality, ozone and UV radiation, and climate monitoring and forecasting.

What is the GRACE mission, and what does it do?

The GRACE (Gravity Recovery and Climate Experiment) mission is a NASA mission that uses two identical spacecraft to map Earth's gravity field by making accurate measurements of the distance between the two satellites, using GPS and a microwave ranging system.

What is the objective of the Sentinel-5 mission?

The objective of the Sentinel-5 mission is to globally monitor key air quality trace gases and aerosols using a passive grating imaging spectrometer.

What is the objective of the Sentinel-6 mission?

The objective of the Sentinel-6 mission is to measure mean sea level and ocean sea state using synthetic aperture radar and multi-frequency Advanced-Microwave Radiometer for enhanced measurements of atmospheric parameters in the coastal zone.

How does the GOCE satellite measure the Earth's gravity field?

The entire GOCE satellite is the measuring instrument that uses an internal gradiometer mounted at the heart of the satellite close to the center of mass to measure the gradient of the magnetic field.

What is Lidar?

Lidar is a remote sensing technology that uses laser light to measure distances to objects.

What is an active sensor?

An active sensor is a type of sensor that emits energy, such as sound waves, light, or microwaves, and detects the energy that is reflected or scattered back.

How is distance measured using Lidar?

Distance is measured using Lidar by emitting a pulse of light from the scanner and recording the time it takes for the reflection of that pulse to return. Using the speed of light, the distance can then be calculated.

How is position determined using Lidar?

To determine position using Lidar, the origin point in the scanner, azimuth of the laser, and inclination of the laser at the time of measurement are needed. Using trigonometry, the position of the point received from the measurement can then be calculated.

What are the different coordinate systems used in Lidar?

The different coordinate systems used in Lidar are local or scanner's own coordinate systems, project coordinate systems, and global coordinate systems.

What are the components of an airborne Lidar system?

The components of an airborne Lidar system include the Lidar sensor itself, GPS receivers, inertial measurement units (IMU), and computers to record all the height information.

What is the frequency range used by Lidar?

The frequency range used by Lidar ranges from 50,000 (50k) to 200,000 (200k) pulses per second (Hz).

What is Doppler Lidar?

Doppler Lidar is a type of Lidar that uses the Doppler effect to measure velocity, allowing for the measurement of wind speed and direction.

What is the ICP algorithm used for in Lidar?

The ICP algorithm is used to minimize the difference in position between two point clouds/meshes.

Why is overlap reduction important in Lidar?

Overlap reduction is important in Lidar to reduce variations in data density, which can cause unnecessary data and issues when processing.

What is Delaunay Triangulation?

Delaunay Triangulation is a type of triangulation that connects points in a point cloud to create a solid surface made of linked triangles. It is used to create a mesh.

What is SAR?

SAR stands for Synthetic Aperture Radar, which is a microwave imaging system used in remote sensing.

What is INSAR?

INSAR stands for Inferometric Synthetic Aperture Radar, which is a technique used to extract distance information about the Earth's terrain using SAR.

What is the phase of a SAR image determined by?

The phase of a SAR image is primarily determined by the distance between the satellite antenna and the ground targets.

What is Differential Interferometry (DInSAR)?

Differential Interferometry (DInSAR) is a methodology used to map surface deformation patterns by comparing the phase shift related to topography between two interferograms generated from two slightly different sensor positions.

What are the three Vs of Big Data?

The three Vs of Big Data are Volume, Velocity, and Variety.

What is the definition of Volume in Big Data?

Volume refers to high volumes of low-density, unstructured data, ranging from terabytes to hundreds of petabytes.

What is the definition of Velocity in Big Data?

Velocity refers to the rate at which data is received and acted upon.

What is the definition of Variety in Big Data?

Variety refers to the types of data that are available, including text, audio, video, seismic, well data, and satellite imagery.

What is metadata in the context of Big Data?

Metadata is data about data, which provides context and meaning to the actual data.

What is the Square Km Array, and what is the amount of data it produces?

The Square Km Array is the world's largest radio telescope that comprises thousands of dishes and up to a million low-frequency antennas. It produces approximately 160 gigabits per second of data from each radio dish to a central processor.

What is data mining?

Data mining is the process of finding anomalies, patterns, and correlations within large data sets to predict outcomes.

What is a database?

A database is a computerized system that allows you to search, select, and store information.

What is a GIS database?

A GIS (Geographic Information System) database is designed to capture, store, manipulate, analyze, manage, and present all types of spatial or geographical data.

What are the types of databases?

The types of databases include navigational, relational, entity-relationship, object, and document-oriented databases, among others.

What is the Network Model of databases?

The Network Model of databases refers to a way of accessing data, including network, hierarchical, and graph, where data is represented by a series of nodes.

What is the Hierarchical Model of databases?

The Hierarchical Model of databases refers to a more structured way of accessing data, where some nodes are duplicated, and it was a popular approach in the 1970s.

What is the Relational Model of databases?

The Relational Model of databases stores data as tables, and relationships are dynamically defined by queries using SQL (Structured Query Language).

What are Lidar case studies used for?

Lidar case studies are used to create 3D maps of Earth's surface, which help in various applications such as forestry, geology, urban planning, and archaeology.

What is the definition of metadata in the context of Lidar?

Metadata in Lidar refers to information about the sensor's settings and the acquisition date and time, which is useful for data processing and quality control.