[Crm-sig] Issue 388 measuring position
martin at ics.forth.gr
Mon Mar 1 22:19:58 EET 2021
I revise my previous proposal for measuring positions:
Any position measurement is based on triangulation with multiples
distances to reference points and angle measurements. GPS measures
distances to satellites. Distances are Dimensions. If directed distances
use georeferenced directions, i.e. angle to the rotation axis of earth,
etc. angles are again dimensions. Hence, a position measurement is an
evaluation of a combination of multiple associated distance and angle
measurements from a particular spot to certain reference points of known
position in the same reference space. If stars are used, they constitute
(extremely) distant reference points. Gravity and Earth Magnetic Field
also provide reference directions for angle measurements that do not
need a second reference point. Classical longitude measurements use
temporal simultaneity of a common event with a reference location, which
evaluates to an angle. All methods are fairly complex, but the details
are a standard routine or even hidden in a modern GPS module.
Therefore we argue that position measurement is a specific (composite)
observation which results in a position expression, but the constituent
dimensions may or may not be documented.
Hence, P40 observed dimension (was observed in): E54 Dimension may not
All position measurements are approximations of other places. Therefore,
they result in a declarative place defined by an E94 Space Primitive.
Since in general we talk about moving reference spaces, moving things
and evolving processes, the time of measurement is essential. We take it
either to be the time-span of the measurement, or a narrower time-span
which covers the contributing time-critical observations. In essence,
this defines a declarative spacetime box (volume), which again is an
approximation. It appears to me that such an approximation would
normally be used to determine parts of the extent of some instance of
Presence by overlap, coverage or containment.
Sxxx Position Measurement
Subclass of: E16 Attribute Assignment
Scope note: This class comprises activities of measuring positions
in space and time. The measured position is intended to approximate a
part or all of the extent of the presence (instance of E93 Presence) of
an instance of E18 Physical Thing or E4 Period of interest, such as the
outer walls of an excavated settlement, the position of a ship sailing
or the start and end of athlete’s run in a competition.
Characteristically, a theodolite or GPS device may be positioned on some
persistent feature. Measuring the position of the device will yield an
approximation of the position of the feature of interest. Alternatively,
some material item may be observed moving through a measured position at
a given time.
A position measurement is an evaluation of a combination of measurement
of multiple associated distances and/or angles (instances of E54
Dimension) from a particular spot to certain reference points of
previously known position in the same reference space.Often, the
observed constituting dimensions are not documented, or hidden in an
electronic device software.The measured position is given as an E94
Space Primitive corresponding to a declarative place. Together with the
measured time-span covering the time-critical observations it forms a
spacetime volume, which should normally overlap with the spatiotemporal
extent of the thing or phenomenon of interest.
Oxx1 determined position (was determined by): E94 Space Primitive
Oxx2 has validity time-span (is position validity for): E52 Time-Span
We may now formulate the approximation to the things of interest, e.g.
Oxx3 overlaps with presence: E93 Presence.
But the time=span of this presence is already implicit in the time-span
If we use:
Oxx3 overlaps with presence of: XXXX, we need a property for E18 and
another for E4…
Another use case is when someone wants to determine if she is at a
particular declarative place: Fisherman now mark positions in the sea
with GPS, in order to return to the same spot...
To be discussed!
Dr. Martin Doerr
Honorary Head of the
Center for Cultural Informatics
Information Systems Laboratory
Institute of Computer Science
Foundation for Research and Technology - Hellas (FORTH)
N.Plastira 100, Vassilika Vouton,
Email: martin at ics.forth.gr
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