Location Flashcards
What is location
Location serves to ask and answer where questions.
E.g. where is Santa Barbara
What does location require?
Location, which is answering ‘where questions’ required spatial referencing.
One located something by relating it spatially to something else.
Why is a figure and a ground needed in the act of locating?
The something that needs locating acts as a figure and the something else acts as a ground against which the figure gets located with a SPATIAL REFERENCE.
The role of the figure is played by whatever one wants to locate at a given time, and the role of a ground can be played by almost anything else, occasionally by multiple entities at the same time.
What are different types of spatial relation?
Typical relations are: Containment Proximity Adjacency Betweenness Distance
E.g locating a traffic accident in a part of a town, at a highways intersection, between two intersections etc.
What are the types of spatial referencing?
Spatial referencing can be as hoc (also called relative) using any available ground and relation.
Can also be systematic, (also called absolute) using the grounds and spatial relations provided by a spatial reference system.
Give an example of ad hoc and systematic spatial referencing.
Locating Santa Barbara at the bottom of the San Ynez mountains is as hoc, locating it at some latitude and longitude is systematic.
Information systems typically use systematic spatial referencing is standard coordinate systems.
What are the characteristics of a location?
A location is the RESULT of a spatial reference.
For example, locating Santa Barbara through latitude and longitude (spatial relation to the prime meridian) results in a location that is a POSITION on the earths surface. Locating at the bottom of the San Ynez mountains results in the location of a region.
This, locations are treated independently of what they are locating, as purely spatial values.
Difference between positions and regions as locations
Positions are primitive, non-decomposable locations, such as points or coordinated in cells or rasters. Regions are extents, possibly having holes or separate parts.
E.g. Italy’s location as a region that includes islands. And excludes territories like the Vatican City
Locations can also be linear, like parallels of latitude or axes of roads and rivers
Difference between instants and periods of time as factors of location
Time at which something is considered a figure or a grounds can be an instant or a period analogous to the positions and regions in space, instants are primitive and non-decomposable (e.g. now) and periods are intervals (the 1840s). Time remains implicit in location information and can be defaulted to now.
What is a place?
A place is a location that gets named (e.g Downtown Santa Barbara) or described ( the place we lived previously).
What does naming a place enable?
Names give locations a shared identity, and turns places into OBJECTS, capable of participating in relationships, forming networks, and holding events.
Names enable recursive locating, e.g. locating buildings near downtown Santa Barbara refers to downtown Santa Barbara as a place and uses it as a grounds for spatial location.
What is location data
Location data specify what is located (the figure) and what locates it (the grounds) and how the two are related (a spatial relation).
When no figure is specified, the data describe a location by applying a spatial relation to the ground ( expressed qualitatively through prepositions or quantitatively through distance)
When can a ground only remain implicit?
If it is established be a spatial reference system or a context
Examples of systematic and spatial referencing.
A company using ZIP codes to record the location of clients, spatial relation of containment as clients are located systematically inside the zip code region, using the reference system of zip codes. Time defaults to present.
A museum catalogue describing where some specimens are found. Specimen records specify the grounds, and spatial relation is defaulted to proximity (near a spring) which specifies figure, and located as hoc, neighbourhood of each geographic feature
What is a spatial reference system
A spatial reference system systematises spatial referencing by fixing grounds (for example, the equator or the prime meridian), spatial relations (for example, angles) dimensions (for example, the two orthogonal dimensions of latitude and longitude) and measurement (for example, degrees).
They provide a unique and unambiguous interpretation of location data.
What is the ISO
The ISO standards for spatial referencing distinguish systems by referencing coordinates, referencing geographic identifiers and linear referencing.
What are the three types of systematic spatial referencing
Coordinate systems
Geographic identifiers
Linear referencing
How do coordinate systems represent locations?
They allow for representing locations in terms of coordinated, each expressing a distance or angle from a plane orthogonal to coordinate axis.
How does WGS84 represent location information?
WGS84 is a geographic coordinate system that establishes a global ellipsoid carrying a coordinate grid. The coordinate angles are measured front he equator and a conventionalised prime meridian.
What is required to relate coordinates to the physical earth?
A geodetic datum is required to fix the degrees of freedom (the translation and rotations) one has in placing an ellipsoid grid in three-dimensional space. Geodetic Fatima allow for transformation between different coordinate systems (between geographic and state plane coordinates).
What are planar coordinates?
Planar coordinates result from projecting ellipsoid coordinates to a plane or establishing an independent local coordinate system. They simplify distance and direction calculations at the cost of giving up coverage of larger regions through a single set of coordinate axes.
How do you reference by geographic identifier?
This characterises locations by labels or codes. E.g. place names or ZIP codes. Reference systems for names are called gazetteers, and classify places into types and translate each place name into a location expressed through coordinates. E.g. Ptolemy’s gazetteer.
How do you reference using linear referencing?
Linear referencing allow for indicating positions along linear objects, such as roads or rivers. They are used to record where along a linear object attribute changes or some event happened (car accident). Can handle sideways offsets, (like water valves off a tube).
If a geometric description of referenced objects is available, linear references can be translated into coordinates.
What is an example of referencing by identifiers
Addresses use spatial referencing by identifiers (street and city names and postal codes) as well s linear referencing (building numbers) to locate houses businesses etc.
