Geodata Acquisition
Geodata Acquisition was a course I took as part of the module „Methods in Geoinformatics“. The course provided a broad overview of data aquisition techniques (satellite systems, orbits, UAVs, precision, …). In this entry, you can find a selection of the contents I learned and worked on. A second course from this module was on Advanced Remote Sensing, which was more concerned on the processing of the aquired data, while Geodata Acquistion was rather concerned with the data aquisition as such. There can be overlaps, though.
Forms of Geodata Acquistion
Primary Data Aquistion
Primary data acquisition in Geoinformatics involves collecting original spatial data directly from the source. This includes field surveys using GPS to record locations, remote sensing through satellites or drones to capture images, LiDAR scanning for detailed elevation models, and mobile mapping with sensor-equipped vehicles. Examples are drone imagery of farmland or GPS tracking of wildlife.
Secondary Data Acquistion
Secondary data acquisition uses existing datasets gathered by others. It often involves downloading data from open portals, digitizing features from maps, integrating multiple data sources, or accessing data through web services and APIs. Common examples include OpenStreetMap data, government land cover datasets, or census statistics.
Aerial imagery
Aerial imagery is a data acquisition method that captures spatial information from the air using drones, airplanes, or satellites equipped with cameras or sensors. It provides wide-area coverage and detailed images useful for mapping landscapes, monitoring environmental changes, and urban planning. This approach allows for efficient collection of data over large and often inaccessible areas.
Terrestrial Surveying
Terrestrial surveying involves collecting precise geospatial data directly from the ground using instruments like total stations, GNSS receivers, and laser scanners. It focuses on measuring exact positions, distances, and elevations of specific points or features. Terrestrial surveying is essential for detailed mapping, construction projects, and validating data obtained from aerial sources.
This is what we did during my intership at Esri, when we visited and mapped seagrass at the Wadden Sea.
GNSS and Positioning
GNSS, or Global Navigation Satellite Systems, are satellite-based technologies that provide precise location and timing information anywhere on Earth. They enable users to determine their exact position by receiving signals from a network of satellites. GNSS is widely used in mapping, navigation, and geospatial data collection.
National satellite systems for navigation:
- Galileo (ESA, Europe)
- GPS (= Global Positioning System, NAVSTAR-satellites, NASA, U.S.)
- GLONASS (Russia)
- BeiDou (China)
Trilateration
Trilateration in GNSS involves measuring the distance from at least four satellites to accurately determine a receiver’s position. The receiver calculates how long the signals take to travel from each satellite, which translates into distances. By finding the point where these distance spheres intersect, the receiver can pinpoint its exact location in three-dimensional space. Using four satellites allows the system to also correct for timing errors in the receiver’s clock, ensuring precise positioning.
Precision and influential factors
Precision in GNSS refers to how accurately a receiver can determine its position. It is influenced by factors such as satellite geometry, signal quality, atmospheric conditions, and multipath effects where signals bounce off surfaces before reaching the receiver. Better satellite arrangement and clear signals typically improve precision, while obstacles like buildings or trees can reduce it. Additionally, the quality of the receiver’s hardware and software also plays a role in achieving high accuracy.
Multispectral imagery, RADAR, LiDAR, data-processing…