Estimated reading time: 5 minutes
Table of contents
Data collection can happen either directly in the field or from a distance. When data is collected directly in the field, it’s called in situ data. When data is collected from a distance, it’s known as remote sensing data.
In Situ Data Collection
In situ data collection involves scientists going out into the field to examine phenomena directly. They might use various instruments, known as transducers, to measure different physical quantities. Transducers convert physical variations, like pressure or brightness, into electrical signals. Here are some examples:
- Thermometer: Measures temperature of air, soil, or water.
- Spectrometer: Measures spectral reflectance.
- Anemometer: Measures wind speed.
- Psychrometer: Measures air humidity.
These instruments can record analog signals, which are often converted into digital values using analog-to-digital conversion procedures.
It’s important to note that in situ data collection doesn’t always require direct contact with the object. For example, a spectrometer can measure electromagnetic radiation (EMR) reflected by the Earth’s surface without touching it. However, since the data is collected by traveling to the study site, it is still considered in situ data.
Remotely Sensed Data Collection
Remote sensing involves collecting information about an object or area without direct contact and without traveling to the study site. This is achieved using specialized instruments that detect electromagnetic radiation (EMR). EMR is a form of energy that reveals its presence through observable effects when it interacts with matter.
The majority of remotely sensed data for Earth resource applications comes from sensors that record electromagnetic energy. Initially, this data was collected using aerial cameras on photographic films. Today, satellites equipped with electronic sensors are the primary platforms for measuring various physical and biophysical properties of the Earth, such as land cover, elevation, and temperature.
Test Your Knowledge with MCQs
1. Which of the following is NOT an example of in situ data collection?
(a) Measuring air temperature with a thermometer
(b) Measuring wind speed with an anemometer
(c) Measuring spectral reflectance with a spectrometer
(d) Measuring Earth’s surface temperature from a satellite
2. What type of data is collected directly in the field by scientists?
(a) Remote sensing data
(b) Satellite data
(c) In situ data
(d) Electromagnetic data
3. Which instrument is used to measure air humidity?
(a) Thermometer
(b) Psychrometer
(c) Anemometer
(d) Spectrometer
4. How is data collected in remote sensing?
(a) By sending scientists to the field
(b) By using instruments that detect electromagnetic radiation
(c) By analyzing physical samples in a laboratory
(d) By conducting surveys and interviews
5. What is the primary platform used today for remote sensing data collection?
(a) Airplanes
(b) Drones
(c) Satellites
(d) Balloons
6. Which of the following is NOT an example of a transducer used in in situ data collection?
(a) Thermometer
(b) Satellite
(c) Anemometer
(d) Psychrometer
7. What type of signal is often converted into digital values using analog-to-digital conversion?
(a) Electromagnetic signals
(b) Digital signals
(c) Analog signals
(d) Binary signals
8. What is the main difference between in situ and remote sensing data collection?
(a) In situ data is collected directly in the field, while remote sensing data is collected from a distance.
(b) In situ data is collected using instruments, while remote sensing data is collected using satellites.
(c) In situ data is used to study the Earth’s surface, while remote sensing data is used to study the atmosphere.
(d) In situ data is more accurate than remote sensing data.
9. What type of energy is detected by instruments used in remote sensing?
(a) Sound energy
(b) Thermal energy
(c) Electromagnetic radiation
(d) Kinetic energy
10. Which of the following is an application of remote sensing data?
(a) Measuring crop health
(b) Monitoring deforestation
(c) Assessing natural disasters
(d) All of the above
Answers: 1. (d), 2. (c), 3. (b), 4. (b), 5. (c), 6. (b), 7. (c), 8. (a), 9. (c), 10. (d)
FAQs
In situ data collection involves direct measurements taken in the field using instruments like thermometers and anemometers. Remote sensing, on the other hand, gathers data about an object or area from a distance, typically using satellites or aircraft equipped with sensors that detect electromagnetic radiation.
Remote sensing offers several advantages, including:
Broad Coverage: It can collect data over large areas, making it ideal for monitoring environmental changes, mapping land use, and assessing natural disasters.
Timely Data: Satellites can provide frequent and consistent data updates, enabling near-real-time monitoring.
Cost-Effectiveness: While initial setup costs can be high, remote sensing can be more cost-effective than deploying scientists to the field for extensive data collection.
Remote sensing data collection faces challenges such as:
Atmospheric Interference: The Earth’s atmosphere can distort or obscure the electromagnetic signals, affecting data quality.
Sensor Limitations: Sensors have limitations in resolution and accuracy, which can impact the level of detail in the collected data.
Data Processing: Remote sensing data often requires complex processing and analysis to extract meaningful information.
