elevation-spec's Introduction

Elevation Service Specification

Gross Specification

Feature	Status
Works through Apache.	Done
Uses HTTP GET from an endpoint.	Done
If `/proc/loadavg > 5` then return `503 Service Unavailable`.	Not Done
HTTP cache headers are based on the latest date of the data sources.	Not Done

Data Sources

Source	Currently Included
SRTM	Yes
Nova Scotia DEM	No
NYC DEM	No
Canadian Elevation Data API	No

Request Parameters

Name	Description	Example	Status
bbox	`minlong,minlat,maxlong,maxlat`	`bbox=4.06,50.86,5.13,51.33`	Done
format	```rdf/xml	n3	ntriples
scale	Distance between points in metres.	`scale=90`	Done

Note: format arguments are either format=rdf/xml|n3|xyz|png or controlled through an HTTP Accept header. Any error on this parameter is reported as 406 Not Acceptable.

Provenance Information

RDF Provenance information has to be created for each data source.

Status: Not Done

Example:

<prov:Collection rdf:resource="http://localhost/answer/xx">
  <rdf:type rdf:resource="void:Dataset"/>
  <prov:wasGeneratedBy>
    <prov:SoftwareAgent rdf:about="http://localhost/api/xx" >
      <prov:wasGeneratedBy rdf:about="http://localhost/api/about" />
      <rdfs:label xml:lang="en">Elevation Server API process ID xxxxx</rdfs:label>
      <prov:startedAtTime>2014-07-14T01:01:01Z</prov:startedAtTime>
      <prov:endedAtTime>2014-07-14T01:01:03Z</prov:endedAtTime>
      <prov:wasInformedBy rdf:resource="http://localhost/api/datasets/A"/>
      <prov:wasInformedBy rdf:resource="http://localhost/api/datasets/B"/>
      <prov:wasInformedBy rdf:resource="http://localhost/api/datasets/C"/>
    </prov:SoftwareAgent>
  </prov:wasGeneratedBy>
  <prov:hadMember>
    <!-- This point extracted from another dataset. -->
    <geo:Point rdf:resource="http://localhost/answer/point/xx">
      <geo:long>....</geo:long>
      <geo:lat>....</geo:lat>
      <prov:wasInformedBy rdf:resource="http://localhost/api/datasets/A"/>
    </geo:Point>
  </prov:hadMember>
  <prov:hadMember>
    <!-- This point extracted inferred by an algorithm and another dataset. -->
    <geo:Point rdf:resource="http://localhost/answer/point/xx">
      <geo:long>....</geo:long>
      <geo:lat>....</geo:lat>
      <prov:wasGeneratedBy rdf:resource="http://localhost/api/xx"/>
      <prov:wasInformedBy rdf:resource="http://localhost/api/datasets/B"/>
    </geo:Point>
  </prov:hadMember>
  ...
</prov:Collection>

Permanent Metadata

Permanent metadata hangs off the endpoint as a static document at http://.../endpoint/about.

Status: Not done

Example:

<prov:Activity rdf:about="http://localhost/api/about">
  <rdfs:label xml:lang="en">Elevation Server API Process</rdfs:label>
  <rdf:type rdf:resource="http://www.w3.org/ns/prov#Activity"/>
  <rdf:type rdf:resource="http://purl.oclc.org/NET/ssnx/ssn#Process"/>
  <prov:wasAssociatedWith rdf:resource="http://rdf.muninn-project.org/ww1/2011/11/11/Organization/Muninn"/>
  <foaf:name xml:lang="en">Elevation Server API Process</foaf:name>
  <doap:Version>2.0</doap:Version>
  <rdf:type rdf:resource="http://www.w3.org/ns/prov#SoftwareAgent"/>
  <rdf:type rdf:resource="http://usefulinc.com/ns/doap#Project"/>
  <doap:service-endpoint rdf:resource="http://localhost/api"/>
  <doap:developer rdf:resource="http://localhost/markfarrell"/>
  <doap:homepage rdf:resource="http://localhost/"/>
  <doap:blog rdf:resource="http://blog.muninn-project.org/"/>
  <doap:description xml:lang="en">The Elevation Server API will ...</doap:description>
  <cc:attributionName xml:lang="en">The Muninn Project</cc:attributionName>
  <cc:attributionURL rdf:resource="http://www.muninn-project.org/"/>
</prov:Activity>

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elevation-spec's Issues

RDF and N3 format examples?

What should the response look like when rdf or n3 are selected as formats in a request?

Integrate NYC DEM into data

https://data.cityofnewyork.us/City-Government/1-foot-Digital-Elevation-Model-DEM-/dpc8-z3jc

Tempted to create a void record for this for provenance purposes that lists the original location of the dem.

What permanent metadata should hang off the endpoint http://.../about?

Integrate Nova Scotia elevation data

This may require a little bit more conversion work:
http://novascotia.ca/natr/meb/download/dp055.asp

Integrate the Canadian elevation data API

http://geogratis.gc.ca/site/eng/elevation

Example of RDF provenance information for data source?

Provide an example of RDF provenance information being provided for a data source?

Use PostGIS if we're still able to adjust scale?

I'd recommend using PostgreSQL/PostGIS, taking elevation data from all of those data sources, massaging the data and storing it all in a spatial table of points. We could even include the original data source as a feature of each of the points, as well as the publication date of the data source, useful for doing provenance. We'd basically then have just have a CGI script that queries our geospatial database for all of the points inside of a requested bounding box and serializes the result set of points in a requested format. But my concern is that we would not be able to set the distance in metres between points, the scale parameter in our requests, should we choose to do this. I don't believe this is possible with PostGIS, unless I'm mistaken.