[Crm-sig] Issue 388 measuring position

Martin Doerr martin at ics.forth.gr
Mon Mar 1 22:19:58 EET 2021

Dear All,

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 
be instantiated.

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 
of validity.

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,
  GR70013 Heraklion,Crete,Greece
  Email: martin at ics.forth.gr
  Web-site: http://www.ics.forth.gr/isl

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