Of course, there is no denying that the first stage in any scientific enterprise is observation. If observations or found to be repeated then comes stage of measurement so that observations are collated and used in modelling.

I think the mail problem is using GIS is that the users till dont realise it is a toll for many decision making and the deicision making is as good as the data that is being used. Use of mobile data has not yet been proved to be cent percent reliable and we have to take these data with description and with a pinch of salt

SFCTA used an smartphone app to track cyclist routes and from that gather data as in a OD survey. It proved good but not easy as you have to have ways of knowing which data is really off, and which one is useful.

Take a look, http://www.sfcta.org/content/category/12/97/483/

Also openstreets map uses this principle to build maps all around the world, and it has really good data. http://wiki.openstreetmap.org/wiki/Main_Page

I guess as Jayakumar pointed out, the quality of the data will be influenced by how involved are users, and how much they know of what they are doing and their repercussions.

As all of you have rightly remarked that the data base used are not reliable. Being in this line since 1996 what I have realized is that data is like a foundation for all days to come. If there is error - we are building our blocks on the erroneous system - likely to mislead, bring in problem and can collapse a system.

Hence it is high time that all should endevour that the quality of data and mainly because we are looking at spatial perpective - it should be correct as far a possible.

Hi pals ., the initiation has already been taken by a Chennai based open source group who r pursuing Master's degree at Anna University. They are now having the data of all the mobile nos.of their student community , Facebook links with approx. Lat. and Long. plus the cadastral map created using our Cartosat image , a process of crowd sourcing is been done ., they exactly showed the peak line is found at 8-9 AM in Guindy where the ground truth matched accordingly. Also Planning to track the crowds at public avenues , cinemas , railway station., but i cannot say this is a sustainable method ., unless govt. installs full street cameras, gps signal taken from the telecom line from almost every individual., a team has to be working vigorsly to change the scenario., ---Results will be great ., creation of theft map , planning to even map the most corrupted places of chennai ...with their identities...

Its possible to produce quality data ., we might have read so many research papers , articles ., try to make a similar research in ur leisure time to validate the result and post it along with the ISSN no. for reference., so that fellow students would concentrate on the real and innovative part of the research work ., who knows one day that idea can change the face of the nation......

Just see Open Street Maps which is purely based on VGI and is now being used by Apple and many others. The key is the correction of wrong data by the other contributors. Today with the rapidly changing landscape VGI is the only source of current information. To this extent National Mapping Organisations worldwide are using VGI to update their maps.

Can you be specific with examples of data. However data integrity is a function of application you are aiming at. Updating the GIS database with such data should be avoided.

As it is clear, sometimes you dont have a reliable source of data and you should be dependent on the indirect resources. Europe is using mobile source of data for telecommunication to estimate the congestion and traffic problems. I think the data from crowding could be a reliable indirect source for social dynamic data.

Yes, Of cours, but i the pepople are one element out of othe crowd sours, it is necessary to consider that there is any other crow source.

As it has mentioned earlier, poor data is better than no data in some cases. Researchers just have to be careful to not over state the results from such data as it may have many errors. Just as those in the Pychology field have to rely on self-reported data (which have been proven to produce inaccuracies), GIS scientists can use these data to produce products that can be valuable to governments and commercial enterprises. Since such data is easy to collect, large databases can minimize the error in the data set, making it more reliable.

On top of VGI I guess this is more about UVGI (UnVolunteered Geographical Information) and the interpretation made from it. It raises new problems and challenges (besides the VGI ones on quality which still remain) such as the representativity (spatial sampling): for example Twitter, on your mobile phone, by default is not geo-located (you need to turn this on) ... it raises also also more privacy problems (see Javid Javidnia input about mobile source data for traffic congestion) ... actually commenting on the social dynamic sourced this way, I think there are difficult sampling biases to sort out before concluding on social dynamic .... I guess for congestion traffic this is fine as long as on knows that the estimates will be the minima of congestion but further social analysis will be difficult ... so challenging spatial data mining, geosemantic mining with necessary multiple geospatial data sources mashups in order to extract relevant information!

http://senseable.mit.edu/papers/pdf/RattiPulselliWilliamsFrenchman2005E&PB.pdf This contains information about an effective presentation I saw, depicting the usage of mobile phones during the soccer finals, in Italy, depicted as layers in the air.