Request for help: BP 9 "How to describe relative positions"

Hi-

BP doc section § 10.5.1 "Describing location" [1] is where we intend to
provide all the guidance that explains how you should encode location
information in a web-friendly way.

This includes BP 8 "Provide geometries on the Web in a usable way" [2] and
BP 9 "How to describe relative positions" [3].

(I think it's likely that we will also need a BP to help people choose the
right CRS too ...)

We editors envisage BP 9 covering:

(1) Linear referencing
(2) Use of spatial relations [4]

...

(1)
>From a quick scan, I see that ISO 19148:2012 covers the topic of Linear
Referencing. I don't have access to the ISO document itself, so I've not
been able to read the standard ... but reviewing the UML model (accessible
here [5]) it seems VERY complicated.

I also note that the INSPIRE Generic Network Model has a simpler
implementation of Linear Referencing.

Questions:
a) are we limited to GML implementations for Linear Referencing?
b) has anyone converted the GML Application Schemas from ISO 19148 and
INSPIRE GNM into other formats ... particularly an RDF / OWL ontology?
c) are there any other mechanisms in use for Linear Referencing? e.g. can
LR be done with GeoJSON?
d) are people really using ISO 19148:2012 given it's complexity?

INSPIRE's Transport Network specification v3.2 §10.3 "Linear Referencing"
states:

“In general it is expected that linear referencing will be used to model
the relationships of objects that are associated with an network, but where
the position of those associated objects is not known (or required) to a
very high level of absolute accuracy ~ better than 1-3m at local level
(e.g. traffic accidents, planned works, restrictions).

Where absolute accuracy is required (e.g. the location of drain covers,
excavations, line side signalling equipment, masts etc) such objects should
be reused, and referenced, if they already exist e.g. as topographic
features.”

This seems like the basis of some guidance about when one might use Linear
Referencing.

What I need (please!) are some worked examples for Linear Referencing of a
point along a linear feature and for Linear Referencing of a length along a
linear feature. In the flooding scenario, this might be:
* Location of flotsam / debris (point) blocking a drainage channel that
needs to manually cleared
* Location of a flooded section (length) of a road

(2)
We also want to demonstrate how spatial relations are used. There are
obvious examples of topological relationships such as "this administrative
unit _touches_ that administrative unit" (or contains etc.).

I recall that we were going to get the set of topological relationships
added to the IANA Link Relations registry [7]. I am not even sure which set
of topological relations we should be recommending? GeoSPARQL has me
somewhat confused with "Simple Features Relation", "Egenhofer Relation" and
"RCC8 Relation". Then there's D9-EIM too ...

Can someone provide me some worked examples using the preferred set of
topological relationships?

We also need to illustrate use of _directional_ (e.g. "left", "in front of"
and "astern") and _distance_ relations (e.g. "at", "nearby" and "far
away"). I don't know of any formalised vocabulary for expressing these
things. If there is one, should we be seeking to add these to the IANA Link
Relations registry too?

Again, worked examples requested! If you can related them to an urban
environment / flooding scenario all the better. (e.g. someone might assert
"the flooding is near my house")

Finally, we also need to show people how to express "fuzzy" spatial things.
Examples we have elsewhere in the BP doc are "the American West" and "
Renaissance Italy". These are spatial things were there is not general
agreement about the exact geographic extent, so it is not possible to use a
geometry to describe it. What is the best way to describe things like this?
Should we use spatial relations e.g. "downtown" _contains_ city districts
A, C, D, and G (because "everyone" agrees this) - but we're not saying it's
exact geometry because it's a colloquial term used by citizens of our
fictional Nieuwhaven.

Again, I'd like to see a worked example.

...

There's a lot of questions wrapped up in this email. I'm looking for help
to resolve them ... preferably with someone in the WG taking the lead to
coordinate a response.

I'm also aware that we need to avoid an RDF bias, so it would be good to
have examples in other formats too.

Volunteers, please step forward!

Thanks in advance. Jeremy

[1]: http://w3c.github.io/sdw/bp/#bp-expr-geo
[2]: http://w3c.github.io/sdw/bp/#describe-geometry
[3]: http://w3c.github.io/sdw/bp/#relative-position
[4]: http://w3c.github.io/sdw/bp/#spatial-relations
[5]: https://github.com/ISO-TC211/HMMG
[6]:
http://inspire.ec.europa.eu/documents/Data_Specifications/INSPIRE_DataSpecification_TN_v3.2.pdf

[7]: http://www.iana.org/assignments/link-relations/link-relations.xhtml