Test the new geo-synchronization feature also in your desktop computer: unofficial gvSIG Mobile 0.1.5 is out!

You can now test the new synchronization feature also in your Ubuntu or Windows desktop PC/laptop/netbook – and of course on your Freerunner (Linux/Openmoko) or Nokia N800/N810 (Linux/Maemo). Download your installer now!

		Ubuntu (tested on 8.04 and Kubuntu 9.04, also for netbooks)
		Linux/Openmoko for Freerunner/GTA02 (tested on SHR)
		Linux/Maemo (tested on Nokia N810)
		Windows XP/Vista (tested on both)

• Full install instructions here
• User manual here
• Installers are hosted in the project’s Garage page

This is what you will be able to do:

Threesome synchro fest: Freerunner (Linux/Openmoko), Nokia N810 (Linux/Maemo) & Packard Bell notebook (Windows XP)

I have done a synchronization test to effectively edit a remote PostGIS table. This diagram describes the situation:

All three devices are using a wireless connection and are updating the same remote table which in turn is used by the server to render a point layer in raster mode (the server is both a synchro server and a map server). You can see a short video here. The remote synchro/map server is not shown:

You can also visit these websites (click on the logo):

	Tellus project blog
	Open mobile IS website

Editing a remote PostGIS table using Open mobile IS

Open mobile IS (aka Openmis) is a Java open source project (GNU LGPL license) that aims to provide all the necessary tools, API and documents effectively enabling the development of mobile applications – not intended especially for GIS applications. It was created by Philippe Delrieu (Ubikis technical leader, based in Lyon, France) and has been used successfully for almost ten years in CDC and CLDC platforms. It’s listed as a mature project in the OW2 (ObjectWeb) consortium forge.

Manuel Gomez (Ubikis R&D officer) kindly invited me to join the Tellus project (visit its blog here) where he is exploring the integration of Openmis and gvSIG Mobile. There are several ways to integrate these two projects. I propose to add the Openmis client module as part of gvSIG Mobile (ideally as an extension). This diagram gives an idea of how Openmis fits our needs. Click to see larger image:

Openmis provides the synchronization engine, user authentication and encryption (this is only a part of all the components available in the Openmis framework). Synchronization happens at client request. The client side FODB (fast object database) lets the user work in disconnected mode, while the conflict resolver in the server side will decide who ‘wins’ if both sides have updated the same feature since the previous synchronization.

You can see a first test on a PC here.

How far is my boat from the shoreline?

In answer to Lanzo’s message in the Openmoko community mailing list, here is a demo where gvSIG Mobile for Openmoko v. 0.1.4 permanently shows the distance between the user and the shoreline. You only need to provide a line-type shapefile in EPSG:4326 with exactly one feature (the shoreline of your area). In this case, I recommend a vertex every 100 meters or so.

As you can see at the end of this 45-second video, the estimated distance between Plaza San Agustín (Valencia) and the Mediterranean sea is 4790 meters:

Geo-w*nk of the day: Ordnance Survey’s secret heatmaps unveiled

Some countries have an interpolation grid to accurately perform the conversion between EPSG:4326 and their traditional national coordinate system. gvSIG Mobile does not use so far any of these grids. Instead, it simply uses 7-parameter transformations and the standard formulae for projections, which causes a small error when the user watches the GPS arrow on his vector files or remote raster layers (when using a datum other than WGS84).

In the case of the United Kingdom and their national grid (EPSG:27700), an online free conversion service is available via the Ordnance Survey website:

http://gps.ordnancesurvey.co.uk/etrs89geo_natgrid.asp

This conversion claims to have an error of only a few cm, so we can accept it as the ‘official truth’ and compare our results with theirs. With a simple loop one can create a heatmap of Britain showing the divergence between the result given by gvSIG Mobile and the one obtained from the OS service, and here is the resulting heatmap in polar coordinates:

The vector represented is [gvSIG Mobile value] minus [OS value].

For example, the argument color for London is something between blue and cyan. Since blue = 0º and green = 120º, then cyan = 60º and the argument for London is about 45º. In the modulus heatmap, London is in a middle gray, so m = 5.05 / 2 ~= 2.5 m. All this means that, for London, the X (easting) in EPSG:27700 estimated by gvSIG Mobile is about 1.5 meters bigger than the X provided by the OS service and the Y (northing) in EPSG:27700 estimated by gvSIG Mobile is also about 1.5 meters bigger than the Y provided by the OS service.

Areas in black (Dorset & Ross-shire) are the lucky counties: gvSIG Mobile’s result is very accurate. Unlucky (white) counties include Norfolk & Lincolnshire.

New features in version 0.1.4

Unofficial gvSIG Mobile for Openmoko v. 0.1.4 is now available. Check Features and How-tos sections for details about these new features:

Travel guide mode	More finger-friendly GUI & fullscreen mode
.	.
GUI in Arabic, thanks to Nawfal Cherqui	Support for German coordinate systems (EPSG:31466 to EPSG:31469)

With the new ‘Courier Mode’, Openmoko actively guides you through the city

A new feature has been added to the unofficial version of gvSIG Mobile for Openmoko. Simply by providing a shapefile describing the POIs (actually the polygon type is recommended) and a few JPG pictures, the application will show a dialog every 20 seconds with a description of a nearby POI and its relative position (in front of you, behind you, to your right, to your left or you are inside). The user only has to push the image to close the dialog and decide where he wants to go.

This is the tiny polygon shapefile I used in my test:

And here is the demonstration:

This feature will be available in the upcoming 0.1.4 version.

gvSIG Mobile mapping libraries on Android, test #1

The gvSIG Mobile mapping libraries used by the Openmoko/Maemo version can be added without a change to an Android project. I only had to add some 30 lines of code to implement the rendering API using Android’s classes and a few more lines on the UI side, and here is the first WMS/Spherical Mercator demo:

Updating location library

Juan Guillermo Jordán (from the LISITT R&D group, Instituto Robotica, Universitat de Valencia, who is also doing some other nice things) is responsible for the GPS capabilities of gvSIG Mobile. They have been partially included in this unofficial version. The library gvSIG Mobile formerly used to access GPS data was called libGPS (based on the Dinopolis gpstool package) and is evolving to a more flexible one called libLocation which will provide an interface to access a wider range of location data sources.

Juan Guillermo has been kind enough to set up the workspace in his Ubuntu machine and successfully tested libLocation instead of the old libGPS. In his test he is accessing the GPSd running on a remote PC.

That’s the Spanish Cadastre WMS server. He works in that rectangular building in the outskirts of Valencia. I could have asked him for a nicer example, but I like this one because it came spontaneously :)

Sorry for the unreadable font I used to print the coordinates. It looks much better on Openmoko! Needless to say, I will add the new libLocation to my workspace asap ;)

Old things brought to light: a Roman theatre & some orthophotos

Timeline:

• 5 BC. A great Roman theatre is built in Carthago Nova (today Cartagena, in Southern Spain), one of the largest in Hispania.
• 5th century. Hispania becomes a Visigothic kingdom. Many Roman theatres are eventually abandoned and forgotten. Across the Middle Ages, houses are built on top of the ruins of the Cartagena Roman theatre.
• AD 1245. A cathedral is built in Cartagena, partially overlapping the remains of the then-unknown Roman theatre.
• AD 1930. Julio Ruiz Alda produces a series of aerial orthophotos covering parts of South-eastern Spain, including Cartagena. This imagery is served today via WMS by the Confederacion Hidrografica del Segura (first screenshot).
• AD 1938. The mentioned cathedral is destroyed during the Spanish civil war.
• AD 1956. The Spanish government produces a massive aerial orthophoto covering the whole country (second screenshot, served by the Murcia regional authority).
• AD 1988. The Roman theatre is accidentally discovered. Newer buildings on it are removed. Archaeological and restoration works continue up until present day (third screenshot).

Blue shapefile: cathedral
Red shapefile: Roman theatre

1930: The theatre is covered; the cathedral is in good condition

…

1956: The theatre is covered; the cathedral’s roof is gone due to 1936-39 bombings

…

2007: The theatre is uncovered and is being restored; the cathedral was never restored (there is another cathedral elsewhere)