Regular magnifying lens tools come with a disadvantage: They cause discontinuities in the map, they break roads and borders and cover up some underlying areas:

Ordinary magnifying lense effect

Smooth magnifying lens tools solve this problem. The idea is not new:

Conrad Morant (1548)

… but it’s not implemented in any of the widely used toolboxes. In fact, I’m not aware of any implementation up-to-date.

[Harrie, L., Sarjakoski, T., Lehto, L. A variable-scale map for small-display cartography. In: Joint International Symposium on GeoSpatial Theory, Processing and Applications (ISPRS/Commission IV, SDH2002). Ottawa, Canada, July 2002] present an algorithm for a smooth magnifying lens effect.

As barrycarter pointed out on gis. stackexchange, this visualization can be seen as a kind of cartogram and could probably be implemented in a similar fashion. I’d love to see such a tool in QGIS and probably even OpenLayers.

OGC Table Join Service Standard

By underdark

2010-12-16

GIS, OGC

10 December 2010 – The Open Geospatial Consortium (OGC®) announces adoption and availability of the OGC Georeferenced Table Joining Service (TJS) Implementation Standard, Version 1.0. The TJS standard is available for free download at http://www.opengeospatial.org/standards/tjs.

The OGC TJS standard defines an interface for services that provide the ability to join attribute data stored in one database on a network with corresponding geometry (points, lines, or polygons) stored in another network accessible database.

… more

Advanced Layer Styles in QGIS

By underdark

2010-12-15

GIS, QGIS

1 Comment

New symbology has been around for quite a while now, but the last weeks have seen some great new additions to this functionality. Let’s have a look at what can be achieved:

Arrow styles

Using ‘Marker Placement’ options in ‘Marker Line’, we can now create fancy arrows pointing in or against line direction.

Arrow style for line layers using 'Marker Lines' and specialized marker placement

Rails style

Using ‘Marker Line’, we can also create nice looking railway styles. The ‘sleepers’ are created using vertical line markers at certain intervals.

Rail style with 'Marker Line' at certain interval

Polygon styles

Besides normal and SVG polygon fill styles, new symbology now offers centroid and outline styles. Outline styles offer all options found in line style dialog (simple, marker and line decoration).

Fun polygon style using fill, outline and centroid layer

QGIS Symbology Improvements for 1.7

By underdark

2010-12-15

GIS, QGIS, Visualization

QGIS community has developed some interesting new features over the last weeks:

Nathan Woodrow has created a graphical rule builder for rule based vector symbology. Rule based symbologies allow you to create classes of features based on custom rules. Now, you don’t need to write those rules manually anymore.
Martin Dobias has implemented functionality that allows you to treat the outline of polygons as a separate entity. This way, you can render a polygon with one or more line styles. Additionally, you can render a marker on the polygon centroid.

The time of old symbology is running out. It will not be available for QGIS 2.0 anymore, but who will miss it? The development speed of QGIS symbology in the last months has been simply astonishing!

QGIS Christmas Wishlist

By underdark

2010-12-15

GIS, QGIS

This year, the QGIS community is not writing their wish lists to Santa Claus. This year, we get to send our wishes to kCube!

You will find the wish list on the QGIS Wiki. The page is aimed at collecting ideas for features and tasks that can be assigned to the 6 months of developer time being donated by kCube Consulting. Later, there will be a poll to find the most useful contributions.

Have your say and post your ideas! And don’t hesitate to follow kCube’s example ;)

Online Batch Geocoding

By underdark

2010-12-14

GIS

I used to go to batchgeo.com for geocoding address lists, but last time I visited, I couldn’t find where to download the resulting list with lat/lon values.

Luckily, there’s another service available that will do: GPSVisualizer.com. They offer several options for geocoding: single address, address list, and a service for tabular data. Like batchgeo.com, they use Yahoo’s geocoding API to do the actual work.

Facebook Friendship Map

By underdark

2010-12-14

GIS, Visualization

3 Comments

Paul Butler, an intern at facebook, has created a map of facebook relationships. Relationships are represented by great circle arcs connecting the locations of two friends. The result is a great looking map of the relationships on facebook:

Interesting (… but scary)!

Vincos from vincosblog has compiled a series of world maps showcasing the distribution of different social networks worldwide and the changes over the last 18 months. The maps clearly show facebook taking over :

1st Conference on Spatial Statistics 2011

By underdark

2010-12-11

GIS

The “1st Conference on Spatial Statistics 2011” is going to take place from 23rd – 25th of March 2011 at the University of Twente, Enschede, The Netherlands. Topics include:

Mapping global change
Spatial and spatio-temporal statistical methodology
Environmental issues
Ecological and habitat changes
Health and epidemiology
Economy and energy
Image use and analysis
Developing countries

Simple Heatmaps Using Python

By underdark

2010-12-11

GIS, Visualization

http://www.sethoscope.net hosts a really neat Python script for heatmap creation.

The script takes data points with latitude and longitude coordinates (list of points or a GPX track log) and plots them on a map so areas where points are dense show brightly.

Nice extras include: GPX tracks can be rendered as line segments instead of disconnected points. You can generate animations using ffmpeg. The heatmaps can be put on top of OpenStreetMap tiles.

The script is released under AGPL making it free to improve and share.