Archive for the ‘Geo-Indexing’ Category

elasticsearch 0.90.2

Thursday, June 27th, 2013

0.90.2 released by Clinton Gormley.

From the post:

The Elasticsearch dev team are pleased to announce the release of elasticsearch 0.90.2, which is based on Lucene 4.3.1. You can download it here.

We recommend upgrading to 0.90.2 from 0.90.1, especially if you are using the terms-lookup filter, as this release includes some enhancements and bug fixes to terms lookup.

Besides the other enhancements and bug-fixes, which you can read about on the issues list, there is one new feature that is particularly worth mentioning: improved support for geohashes on geopoints:

A geohash is a string representing an area on earth – the longer the string the more precise the geohash. A geohash just one character long refers to an area with a very rough precision: +/- 2500 km. A geohash of length 8 would be accurate to within 20m, etc. Because a geohash is just a string, we can index it in Elasticsearch and take advantage of the inverted index to make blazingly fast geo-location queries.

Wikipedia on Geohash. Numerous external links, including http://geohash.org/. Enter geo-coordinates or a geohash, displays map with location displayed.

gvSIG

Saturday, March 30th, 2013

gvSIG

I encountered the gvSIG site while tracking down the latest release of i3Geo.

From its mission statement:

The gvSIG project was born in 2004 within a project that consisted in a full migration of the information technology systems of the Regional Ministry of Infrastructure and Transport of Valencia (Spain), henceforth CIT, to free software. Initially, It was born with some objectives according to CIT needs. These objectives were expanded rapidly because of two reasons principally: on the one hand, the nature of free software, which greatly enables the expansion of technology, knowledge, and lays down the bases on which to establish a community, and, on the other hand, a project vision embodied in some guidelines and a plan appropriate to implement it.

Some of the software projects you will find at gvSIG are:

gvSIG Desktop

gvSIG is a Geographic Information System (GIS), that is, a desktop application designed for capturing, storing, handling, analyzing and deploying any kind of referenced geographic information in order to solve complex management and planning problems. gvSIG is known for having a user-friendly interface, being able to access the most common formats, both vector and raster ones. It features a wide range of tools for working with geographic-like information (query tools, layout creation, geoprocessing, networks, etc.), which turns gvSIG into the ideal tool for users working in the land realm.

gvSIG Mobile

gvSIG Mobile is a Geographic Information System (GIS) aimed at mobile devices, ideal for projects that capture and update data in the field. It’s known for having a user-friendly interface, being able to access the most common formats and a wide range of GIS and GPS tools which are ideal for working with geographic information.

gvSIG Mobile aims at broadening gvSIG Desktop execution platforms to a range of mobile devices, in order to give an answer to the needings of a growing number of mobile solutions users, who wish to use a GIS on different types of devices.

So far, gvSIG Mobile is a Geographic Information System, as well as a Spatial Data Infrastructures client for mobile devices. Such a client is also the first one licensed under open source.

I3Geo

i3Geo is an application for the development of interactive web maps. It integrates several open source applications into a single development platform, mainly Mapserver and OpenLayers. Developed in PHP and Javascript, it has functionalities that allows the user to have better control over the map output, allowing to modify the legend of layers, to apply filters, to perform analysis, etc.

i3Geo is completely customizable and can be tailor to the different users using the interactive map. Furthermore, the spatial data is organized in a catalogue that offers online access services such as WMS, WFS, KML or the download of files.

i3Geo was developed by the Ministry of the Environment of Brazil and it is actually part of the Brazilian Public Software Portal.

gvSIG Educa

What is gvSIG Educa?

“If I can’t picture it, I can’t understand it (A. Einstein)”

gvSIG Educa is a customization of the gvSIG Desktop Open Source GIS, adapted as a tool for the education of issues that have a geographic component.

The aim of gvSIG Educa is to provide educators with a tool that helps students to analyse and understand space, and which can be adapted to different levels or education systems.

gvSIG Educa is not only useful for the teaching of geographic material, but can also be used for learning any subject that contains a spatial component such as history, economics, natural science, sociology…

gvSIG Educa facilitates learning by letting students interact with the information, by adding a spatial component to the study of the material, and by facilitating the assimilation of concepts through visual tools such as thematic maps.

gvSIG Educa provides analysis tools that help to understand spatial relationships.

Definitely a site to visit if you are interested in open source GIS software and/or projects.

Georeferencer: Crowdsourced Georeferencing for Map Library Collections

Monday, November 19th, 2012

Georeferencer: Crowdsourced Georeferencing for Map Library Collections by Christopher Fleet, Kimberly C. Kowal and Petr Přidal.

Abstract:

Georeferencing of historical maps offers a number of important advantages for libraries: improved retrieval and user interfaces, better understanding of maps, and comparison/overlay with other maps and spatial data. Until recently, georeferencing has involved various relatively time-consuming and costly processes using conventional geographic information system software, and has been infrequently employed by map libraries. The Georeferencer application is a collaborative online project allowing crowdsourced georeferencing of map images. It builds upon a number of related technologies that use existing zoomable images from library web servers. Following a brief review of other approaches and georeferencing software, we describe Georeferencer through its five separate implementations to date: the Moravian Library (Brno), the Nationaal Archief (The Hague), the National Library of Scotland (Edinburgh), the British Library (London), and the Institut Cartografic de Catalunya (Barcelona). The key success factors behind crowdsourcing georeferencing are presented. We then describe future developments and improvements to the Georeferencer technology.

If your institution has a map collection or if you are interested in maps at all, you need to read this article.

There is an introduction video if you prefer: http://www.klokantech.com/georeferencer/.

Either way, you will be deeply impressed by this project.

And wondering: Can the same lessons be applied to crowd source the creation of topic maps?

Using Hilbert curves and Polyhedrons for Geo-Indexing

Thursday, April 5th, 2012

Using Hilbert curves and Polyhedrons for Geo-Indexing

From the AvocadoDB blog:

Cambridge mathematician Richard R. Parker presents a novel algorithm he has developed using a Hilbert curve and Polyhedrons to efficiently implement geo-indexing.

Basic premise is that points that are “near” on the line are also “near” on the Earth’s surface.

Interesting rhetoric but I think the “near” on the Earth’s surface is unnecessary.

More important to observe that a Hilbert curve when “straightened” and indexed, each point cuts across multiple dimensions of “nearness.”

Enables the isolation of “near” points in another representation, say global coordinates, quickly.

Points to consider/research:

  • Basis for indexing/sharding a graph database? An particular n-dimensional Hilbert curve is used for indexing/sharding. Not all queries created equal.
  • How do characteristics of the distances that compose the curve impact particular use cases?