Overview of Geospatial/Geodetic Engineering

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Lead Author: Ulrich Lenk

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This article is part of the Geospatial/Geodetic Engineering (GGE) Knowledge Area. It provides a broad introduction into the overall topic of related applications in order to make the reader aware where those technologies are actually used in systems.

GIS and Geospatial Applications

Perhaps the most comprehensive recent standard textbooks on Graphical Information Systems (GIS) are Longley et al. (2015) and Kresse and Danko (2012). Beyond these two textbooks, there are many others on GIS and respective spatial data capture procedures (surveying, photogrammetry, and remote sensing) and management applications. Tomlinson (2019) and Peters (2012) as well as the online successor to this text book, System Design Strategies, provide valuable insights into aspects of how to set up a GIS system. While Tomlinson (2019) looks more at the management perspective and processes of implementing a GIS, Peters (2012) considers the technical aspects more.

Domain-specific GIS applications are also documented in numerous textbooks. Domain areas include agriculture and forestry, insurance economics and risk analysis, simulation and environmental impact analysis, hydrology, archaeology, ecology, crime investigation and forensics, disaster management and first responders, marketing, municipalities and cadaster, land administration and urban planning, utility sectors, telecommunications, smart cities and military applications. The latter include Command and Control (C2) systems, or are even extended in Command, Control, Communications, Computers Intelligence, Surveillance and Reconnaissance (C4ISR) systems. Generally speaking, wherever data, i.e. information to events that occur, is displayed, processed and/or analyzed in a geospatial context, there is GIS technology involved, whether the user interface is based on a web interface, a desktop client, or a mobile device such as a smartphone or tablet computer. To provide visualization of this data it is necessary to have a spatial context for orientation, geospatial data like digital topographic maps, or geospatial imagery, digital elevation model, etc. Beyond such classical geospatial data, other types of data are also often used, such as meteorological and other environmental data.

Interoperability is of major concern in geospatial technology. The Open Geospatial Consortium (OGC) is probably the most relevant organization that deals with GIS and sensor systems interoperability. The OGC has published a dedicated set of interface specification standards on their topics.

Positioning, Navigation and Timing

The previous description of geospatial technology focused mostly on stationary objects, i.e. non-moving geospatial data. This section is mainly concerned with objects moving in space and with derived applications such as navigation, monitoring, and tracking such objects. The basic operations needed are positioning and navigation. Certainly, the majority of people using smartphones are also using various location based services (LBS) that are provided in conjunction with GIS databases and services, such as Google Maps, a well-known online GIS application. As a consequence, positioning and navigation, which are mainly achieved with Global Navigation Satellite Systems (GNSS), have became ubiquitous and transparent technologies in the last decade. Clearly the most relevant system in common use in the past has been the US Global Positioning System (GPS) since it was the first of its kind. However, it is not the only one of its kind. Russia developed a GNSS called GLONASS; Europe developed the Galileo system which is close to achieving full operating capability; China is working on its Beidhou GNSS. GNSS are not only used for positioning and navigation. Since the range measurements conducted by GNSS are based on extremely accurate one-way travel times of signals, extremely accurate clocks are found in these satellites. GPSS then transmit this time for use by other systems, enabling time synchronization of systems. Together, these three GNSS services are called Positioning, Navigation and Timing (PNT). For more on satellite navigation, two excellent sources are Teunissen and Montenbruck (2017) and Hofmann-Wellenhof et al. (2008).

The public does not generally appreciate how many many systems used in various domains rely on the availability of GPS/GNSS signals. The majority of national critical infrastructure is now dependent on GNSS (Royal Academy of Engineering 2013; Wallischeck 2016). Thus the availability of open access to GNSS signals is nowadays considered a critical infrastructure itself. Example infrastructures and applications depending on GNSS include transport (rail, road, aviation, marine, cycling, walking), agriculture, fisheries, law enforcement, highways management, services for vulnerable people, energy production and management, surveying, dredging, health services, financial services, information services, cartography, safety monitoring, scientific and environmental studies, search and rescue (e.g. as given with the Global Maritime Distress and Safety System, GMDSS), telecommunications, tracking vehicles and valuable or hazardous cargoes, and quantum cryptography (Royal Academy of Engineering 2013).

Geodesy and Geodetic Engineering for Providing the Frames for All Spatial Applications

The above sections are application-oriented. However, at the basic level of modeling, all numerical (coordinate-wise) descriptions of natural and man-made mobile objects, including the ones in space, i.e. satellites, need to be referenced to a coordinate system. It may be a local moving engineering coordinate system, a national coordinate system, a regional coordinate system, or even a world coordinate system, e.g. that given by the World Geodetic System 1984 (National Imagery and Mapping Agency 2004), which is the coordinate reference system in which GPS works. Whereas horizontal coordinates are fairly straightforward since they are mainly based on mathematical assumptions with little input from geophysics (the localization of the rotation axis of the Earth), the third dimension is mostly treated differently since heights are often related to a mean sea level (MSL) surface, which is dependent on the (irregular!) distribution of masses on Earth and thus on their physical properties. The typical surface used for referencing heights is the so-called geoid which may be approximated by MSL. Beyond these Earth related aspects, however, there are also celestial coordinate systems and coordinate systems on other celestial bodies. Torge and Müller (2012) offers more on this. Thus, geodetic engineering with its sub-disciplines of physical and mathematical geodesy together with related engineering disciplines provide fundamental frameworks for various applications in science and technology including systems of systems.

Visualizing Spatial Data with Map Projections and Cartography

Because people often rely on visual depictions more so than on verbal descriptions, the complicated surface of the Earth typically needs to be “pressed” onto a flat screen even when it is a 3-dimensional perspective view on a 2D screen. Depending on the display scale, reducing from 3D to 2D cannot be achieved without certain or even significantly distorting the shape of the objects. Mathematical geodesy and map projections based on differential geometry provide the basics to achieve these goals. (Grafararend et al. 2014). By carefully selecting an appropriate map projection, different characteristics of land masses and applications can be emphasized. One example may be the difference between the classical Mercator projection that is used for nautical charts from the equator up to medium latitudes, and the Stereographic projection that is often used in aeronautics since the shortest distance between two locations there is a straight line. For the Mercator projection, a straight line is the line of constant bearing which eases the use of a magnetic compass for steering a vessel (neglecting variations of magnetic declination on Earth). Here, the shortest distance between two points on the Earth’s surface (the geodesic) is a curved line on the chart whose curve is bent towards the pole of the respective hemisphere.

As visualization of spatial data is a fundamental functionality of GIS, respective map projection modules are always included in GIS software packages. Beyond these purely projection-related aspects of visualizing spatial data, cartography offers rules and procedures for what to display and how to visualize geodata. Kraak and Ormeling (2020) shows such data abstracted as symbols, lines, areas, including what color and styles to apply to the graphical elements in a map, how to relate these to each other on a screen or paper map, how to generalize them when the scale of display is changed, etc.

References

Primary References

Grafarend, E.W., R.-J. You, and R. Syffus. 2014. Map Projections: Cartographic Information Systems, (2nd edition). Heidelberg, New Yort, Dordrecht, London: Springer.

Hofmann-Wellenhof, B., H. Lichtenegger, and E. Wasle. 2008. GNSS - Global Navigation Satellite Systems.Wien: Springer-Verlag.

Kraak, M.-J. and F. J. Ormeling. 2020. Cartography: Visualization of Geospatial Data, (4th edition). London, New York: Taylor & Francis.

Kresse, W. and D.M. Danko (Eds.). 2012. Springer Handbook of Geographic Information. Berlin, Heidelberg: Springer.

Longley, P.A., M.F. Goodchild, D.J. Maguire, and D.W. Rhind. 2015. Geographic Information Science and Systems, (4th edition). New York, Chichester, Weinheim: John Wiley & Sons, Inc.

Peters, D. 2012. Building a GIS: Geographic Information System Planning for Managers, (2nd edition). Redlands, CA: Esri Press.

Teunissen, P. and O. Montenbruck (Eds.). 2017. Springer Handbook of Global Navigation Satellite Systems. Switzerland: Springer International Publishing.

Tomlinson, R.F. 2019. Thinking About GIS: Geographic Information System Planning for Managers., (5th edition). Redlands, CA: Esri Press.

Torge, W. and J. Müller. 2012. Geodesy. Berlin: De Gruyter.

Works Cited

Hahmann, S. and D. Burghardt. 2013. How much information is geospatially referenced? Networks and cognition. International Journal of Geographical Information Science 27(6):1171-1189. DOI: 10.1080/13658816.2012.743664.

INCOSE. 2015. Systems Engineering Handbook: A Guide for System Life Cycle Processes and Activities, (4th edition). San Diego, CA, USA: International Council on Systems Engineering (INCOSE), INCOSE-TP-2003-002-04.

National Imagery and Mapping Agency. 2004. World Geodetic System 1984. (3rd edition, including Amendment 1 and 2). Department of Defense. Technical Report TR8350.2.

Royal Academy of Engineering. 2013. Extreme space weather: impacts on engineered systems and infrastructure. London, UK, Royal Academy of Engineering.

Wallischeck, E. 2016. GPS Dependencies in the Transportation Sector. Cambridge, MA: U.S. Department of Transportation, Office of the Assistant Secretary for Research and Technology, John A Volpe National Transportation Systems Center.

Additional References

Freeden,W. and M.Z. Nashed (Eds.). 2018. Handbook of Mathematical Geodesy: Functional Analytic and Potential Theoretic Methods. . Basel: Birkhäuser.

Meyer, Th.H. 2018. Introduction to Geometrical and Physical Geodesy: Foundations of Geomatics. Redlands, CA: Esri Press.

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