Seminar Report On INTERACTIVE MAPPING A GEOGRAPHICAL VISUALIZATION
Submitted by : SOUMYA S
DEPARTMENT OF COMPUTER SCIENCE
COCHIN UNIVERSITY OF SCIENCE AND TECHNOLOGY
KOCHI-682022
2008
ABSTRACT
Interactive mapping systems are growing in popularity: Microsoft, Google, and Yahoo all offer interactive maps, with varying features and qualities of aerial photography. Mapping systems lack hyperlinks, while other online systems logically lead users between s, online maps can be scrolled and navigated without clicking links. Online maps allows data acquisition teams to concentrate their efforts on the portions of the map that are most seen by users. Online maps represent vast databases, and so it is insufficient to simply look at a list of the most-accessed URLs. Hotmap takes advantage of the design of a mapping systemâ„¢s imagery pyramid to superpose a heatmap of the log files over the original maps. Hotmap is constructed as an AJAX mash-up over Microsoftâ„¢s Virtual Earth API. HotMap shows where people have looked at when using Virtual Earth, the engine that powers Live Search Maps: the darker a point, the more times it has been downloaded
1.INTRODUCTION
A search engine is a co-ordinated set of programs which searches an index and returns matches to a specified keyword. Search engines are tools that can be used to search on the Web, which uses a list-based representation of web search results, that is a sequential evaluation of the document surrogates. One of the interactive search engine is Hotmap ,which is introduced to overcome the shortcomings of list based representation, and it supports the visual exploration of web search results. Interactive in the sense that , the search results can be dynamically resorted based on the query term frequencies. HotMap represents the query term frequencies in the form of a colour-code on a heat scale. Mapping systems are growing in popularity ,because it lack hyperlinks: while other online systems logically lead users between s, online maps can be scrolled and navigated without clicking links. The Google Static Map service creates the map based on URL parameters sent through a standard HTTP request and returns the map as an image can display on the web . Interactive mapping system is achieved by using different techniques such as Event Mechanism and Document Object Model Manipulation in Javascript . Hotmap based on Microsoftâ„¢s Virtual Earth is one of the new generation of interactive mapping services
2. SEARCH ENGINE
Non-Interactive Search Engines Most web search engines use a list-based representation of web search results, promoting a sequential evaluation of the document surrogates. Commonly, these search engines only display ten document surrogates per , limiting the usersâ„¢ ability to explore the search results. But all the 10 documents are not relevant to the particular query message. So users are required to consider many non-relevant documents in the search results before finding the relevant documents. Example: Google.
Interactive Search Engines
Hotmap is introduced to overcome the shortcomings of list based representation, and it supports the visual exploration of web search results. In this the search results are provided at two levels of detail: An overview map that provides a compact and abstract representation of the top 100 documents returned by the underlying search engine A detail window that shows 20 to 25 documents at a time
2.1 HOTMAP
In HotMap, the frequency of each of the query terms from the usersâ„¢ queries are depicted visually using colour coding. This allows the users to easily identify hot documents based on the frequent appearance of the query terms within the document surrogates. In addition to this visual representation, the search results can be dynamically resorted based on the query term frequencies, supporting an interactive exploration of the search results. HotMap is a meta-search system that retrieves the top search results returned by the Google API for a given user query, and presents these results in a compact visual manner that supports both visual information processing and user-directed exploration. HotMap represents the query term frequencies in the form of a colour-code on a heat scale. Multiple occurrences of a query term result in a dark red color; fewer occurrences are represented by progressively lighter shades of red and orange. As shown in Figure 1, this color coding allows the users to see the hot documents easily and provides the inspiration for naming our system HotMap. In HotMap, the search results are presented in a gridbased layout at two levels of detail: an overview map provides a compact representation of the top 100 search results, and a detail window provides a focused view of approximately 20 documents at a time.
A color code in the grid to represent the frequency of the corresponding query term (column) within the corresponding document surrogate (row). Clicking on the column header for a term will re-sort the search results according to the frequency of the corresponding term. Holding down the control key while clicking the column headers generates a nested sorting of the search results according to the ordered selection of the query terms. With respect to the visualization of search results the ultimate goal is to allow users to see the information without having to read the information
3. MAPPING SYSTEM
Online interactive mapping systems are growing in popularity: Microsoft, Google, and Yahoo all offer interactive maps, with varying features and qualities of aerial photography. For the maintainers and designers of such systems, the behavior of users can provide critical cues on how both to improve their offerings and understand how users are now interacting with the system. The tools needed to track user data for these systems are different from the traditional tools of log file analysis. Maps have the advantage of being tied to common-sense geography: a world map. In contrast, many log-file analysis tools must create an abstract space in which to situate a node-link diagram representing the website. Mapping systems lack hyperlinks: while other online systems logically lead users between s, online maps can be scrolled and navigated without clicking links. Applying a log-file analysis tool to these systems fails to represent the relevant dimensions of a mapping system: reconstructing a path between s by examining referrer logs .The analystsâ„¢ understanding of geography can be harnessed to build meaningful log-file visualizations by showing the logs as a map.
3.1 STATIC MAPPING
The Google Static Maps API embed a Google Maps image on the web without requiring JavaScript or any dynamic loading. The Google Static Map service creates the map based on URL parameters sent through a standard HTTP request and returns the map as an image can display on your web .The following example contains the URL of a static map image, which is displayed below: http://maps.googlestaticmap?center=40.714728,-
73.998672&zoom=14&size=512x512&maptype=mobile\
&markers=40.702147,-74.015794,blues%7C40.711614,-
74.012318,greeng%7C40.718217,-73.998284,redc\&key=MAPS_API_
The Google Static Maps API returns a GIF-format image in response to a HTTP request via a URL. For each request, we can specify the location of the map, the size of the image, the zoom level, the type of map, and the placement of optional markers at locations on the map. We can additionally label the markers using alpha characters, so that we can refer to them in a key. We can embed a Static Maps API image within a web inside an <img> tag's src attribute. When the web is displayed, the browser requests the image from the Static Maps API and it renders within the image location.
3.2 INTERACTIVE MAPPING
Hotmap based on Microsoft™s Virtual Earth is one of the new generation of interactive mapping services. It provides both a main mapping site (http://maps.live.com) and a Javascript API for developers to embed the maps in our own site. It provides symbolic maps as well as aerial imagery of the relevant areas. Users can pan and zoom around the map smoothly, drilling from world-wide views down to very zoomed-in views in moments. Both the Javascript API and the front work in similar ways: the browser shows a bounding box and the system downloads appropriate imagery that goes within that box. In the case of Virtual Earth, this is divided into tiles: 256 x 256 images that together show the world. Each of these tiles is requested by the code, and provided by a cluster of tile servers, dedicated machines which provide the imagery to users as they pan and zoom around. The external application can be downloaded as an individual tiles” testing scripts, for example”the vast majority of tile downloads come from users specifically choosing to look at some part of the world. JavaScript is a powerful client-side programming language that helps to develop an interactive maps. Cross-browser support has improved dramatically as standards have evolved, making it a viable choice. For those new to the language, we will find its basic code constructs similar to other mainstream languages like Java. Interactive mapping systems can be developed by using the following methods available in Javascript. Event Mechanism
A powerful event mechanism is included to enable JavaScript to respond to user interactions in the browser. HTML is the JavaScript eventing mechanism in the form of events such as the onclick attribute, as in: <onclick="javascript:myEventHandler(); return true" href="myURL.html">My Link</a> Document Object Model Manipulation Another important feature of JavaScript when executed in the browser is its ability to manipulate the HTML Document Object Model (DOM). This feature allows JavaScript code to programmatically alter the contents of an HTML after it has been loaded. DOM manipulation is an important feature to use when increasing the interactivity of a Web 2.0 application. In Web applications, it is common to reset the text contained by an element in the HTML, as in:
// find the <div> tag with id 'greet_div'
var div = document.getElementById('greet_div');
div.innerHTML = 'Hello ' + name;
The final JavaScript feature that must be mentioned is its ability to issue out-of-band HTTP requests to back-end servers. As a result, JavaScript can issue requests that do not cause the to reload or change the address bar of the browser. This feature is commonly called Ajax, but the source of this feature is the XMLHttpRequest which is the JavaScript class that can invoke the HTTP request. The HTTP requests generally are asynchronous, which requires the programmer to define a callback function to be called when the response is received.
var request = new XMLHttpRequest();
function invokeAjax() {
request.open("GET", 'ajaxTarget.html', true);
request.onreadystatechange = ajaxCallback;
request.send(null);
}
function ajaxCallback() {
// check if response is complete, then do stuff
}
AJAX
AJAX is Asynchronous JavaScript and XML. AJAX is not a new programming language, but a technique for creating better, faster, and more interactive web applications. With AJAX, the JavaScript can communicate directly with the server, using the JavaScript XMLHttpRequest object. With this object, the JavaScript can trade data with a web server, without reloading the .AJAX uses asynchronous data transfer (HTTP requests) between the browser and the web server, allowing web s to request small bits of information from the server instead of whole s. The AJAX technique makes Internet applications smaller, faster and more user-friendly. AJAX is a browser technology independent of web server software.
4 HOTMAP
Hotmap is constructed as an AJAX mash-up over Microsoftâ„¢s Virtual Earth API. The Virtual Earth API includes an ability to superpose translucent tiles from a separate server. Constructing the system as a mash-up has several substantial advantages: as a web , it can be deployed easily; other users can add further data sources over it; and its use can be measured with a server log. Hotmap consists of a server, which serves the around the embedded map; a tile server, which is responsible for returning tile images; and is backed by a database, which stores processed server logs. The input to Hotmap is a sample of Virtual Earth tile server logs. These are trimmed to two core values: a date and a tile identifier. The tile identifier specifies both the location of the tile in space (x, y, and zoom coordinates) and the imagery style of the tile, such as aerial or roads. For performance considerations, the date field is rounded to the nearest day. All tile requests with the same identifier on a given day are aggregated and stored in the database. HotMap shows where people have looked at when using Virtual Earth, the engine that powers Live Search Maps: the darker a point, the more times it has been downloaded. Hotmap is an exploratory data visualization system, which takes advantage of the structure of the underlying data set to visualize it in its own space. In this case, we have examined geospatial imagery, which has the virtue of remaining fixed. When data sets are arranged spatially for users, linking their usage data back can provide important insights into how users approach the data. A heatmap is drawn over a web to show where users looked first. There is no set formula for imagery acquisition; thus, allowing users to reflect on the data from a variety of perspectives allows them to understand and explore the dataset in more depth. Hotmap in Figure 2 provides a social view of the world, mapping a rough notion of popularity. This social view indicates where users find the world to be interesting: what parts of it are worth a closer look? This will allow analysts, researchers, and designers to better understand how users interact with their world.
HOT PLACES
Processing and Visualizing Tile Logs
Tile server logs are standard IIS logs, they store an IP address, a date and time of access, and a URL, as well as several other data points that are not relevant. We aggregate those logs together, producing database records that record only the number of hits on each day for each tile. The tiles are arranged by zoom level, rather than trying to combine information from zoomed-in and zoomed-out data, the maps can conceptually be thought of as distinct. Thus, we will refer to the map at level 10 to mean the server logs describing the usage of the level 10 (approximately 150 meters per pixel, or m/p, scale) tiles. The number of hits at a particular point as its popularity, as a more popular tile is one that has been downloaded more. Hotmap itself generates a number of tile requests and this number become significant. The Virtual Earth tile pyramid illustrated in Figure 3, stores a zoomable image as static tiles, 256 pixels on a side. These tiles are stored hierarchically as a quadtree, with numbered levels from one (78 km per pixel at the equator) to 19 (30 cm per pixel). At the highest level, the entire image”in this case, much of the Earth™s surface, excluding the poles”is stored as four tiles. Hotmap replicates the tile pyramid representation of Virtual Earth for its own data store. This has the advantage of making it easy to render precisely: for level 8 imagery, in which a single pixel corresponds to one tile, the color of a pixel is exactly its degree of popularity. Storing information as latitude/longitude coordinates would require re- projection of the data to the underlying map.
4.1 HEATMAP
Heat maps represent information from databases and spreadsheets visually as rectangles, with important characteristics of individual data items used to determine the size, color and layout of the rectangles. A cell whose color differs strongly from its neighbors indicates an exceptional data value. In Figure 4 , each group divides its area amongst its cells, similar to a pie chart dividing slices of a pie. The difference in size between the largest and smallest cells in a group visually indicates the range of values in that group. The ratio of large to small cells shows how those values are distributed. Heat maps showas this distribution at multiple levels at once. While the cells in each group shows the distribution of values within that group, each groupâ„¢s size relative to the other groups shows the distribution of groups within the data set as a whole. In general: Size maps to relevance, such as the size of an opportunity or the total budget for a project. Color maps to urgency; like the potential upside of an opportunity, the cost or time overrun on a project, risk levels, or the number of security incidents at a network site.
Grouping of rectangles is tied to category information, such as department, manager, location, or type of product or application.
Identify which information is the most important, for example, the opportunities or threats that involve the largest financial impact, since the associated rectangle or group of rectangles is large. See urgent issues such as particularly high risks or overruns, since the associated rectangles have a color that stands out from other data. Discover trends or interesting patterns, such as generally higher or lower performance or risk associated with a particular region, manager, type of product, etc., since grouping related records together spatially allows detailed data represented by size or color to be seen in context. 4.2 DESIGN OF HOTMAP
Traditional use analyses for online systems examine user behavior from a client, server, or proxy point of view. Server-based retroactive log analyses can give detailed information about when a system was used and by whom, but can be confounded by intermediate proxies, firewalls, and aggregators that share IP addresses. In general, these techniques focus on tracking how users moved through the system: they emphasize a notion that users follow links from to , and attempt to track those transitions. The notion of information scent extends this”it suggests that users looking at one web might figure out where to look next based on information on the . Systems like H3 and TimeTube can provide detailed graph- or tree-based visualizations of interaction with a website. A different model comes from tracking how users looked at different portions of a web site, and displaying that information back on the site itself. Several projects have overlaid recent use of a web server on to the web s, separating use into s that have been very recently and not recently read. Annotating maps based on dynamically-collected internet-based data is a newer approach. Many of these have taken the form of mash-ups linking maps to external sources of data. Map mash-ups come in two forms: discrete forms, such as pushpins and poly-lines, in which specific latitude/longitude data is specified and plotted; and overlaid raster images . These have distinct uses: the discrete forms are powerful ways of highlighting a fixed number of points or outlining regions. In contrast, raster images allow the user to assign a value to every pixel. Most recent mash-ups have focused on discrete source data, such as home sales listings and public transit schedules. Raster images, however, allow us to draw heatmaps based on spatial data. A heatmap assigns a color based on a value to each point on a map. Heatmaps are a familiar visualization for maps when data is well-defined for a dense set of samples over space. Heatmaps have also been used to portray social data, although this requires a process of interpolation or extrapolation, as most much information is keyed to survey areas: counties and voting districts. Location-based and map-based systems, which can store latitude/longitude coordinates, have enabled a new type of heatmap visualizations. GIS Geographical Information System (GIS) is an information system that is specially designed for handling spatial (or geographical) data. It combines a set of interrelated software components that create, edit, manipulate, analyse and display data both in text and graphic forms. GIS supports spatial analysis and modeling within the discipline of geography (e.g. location, proximity and spatial distribution), so that it becomes a vital tool for modern geography. GIS is a computer based information system used to digitally represent and analyse the geographic features present on the Earth' surface and the events (non-spatial attributes linked to the geography under study) that taking place on it. The meaning. to represent digitally is to convert analog (smooth line) into a digital form. "Every object present on the Earth can be geo-referenced", is the fundamental key of associating any database to GIS. Here, term 'database' is a collection of information about things and their relationship to each other, and 'geo-referencing' refers to the location of a layer or coverage in space defined by the co-ordinate referencing system.
4.3 HOW USERâ„¢S USE HOTMAP
Narratives of Hotmap Use Hotmap has been deployed internally for slightly over a year, although it has been steadily evolving in conversation with several imagery teams. In order to better understand how tasks are done, three members of mapping teams described how they use Hotmap: Walter1, who makes global decisions about purchasing imagery, Nicholas, who is responsible for coordinating city-scale imagery acquisition; and Jack, who is supervising the recent deployment of a mobile edition of the interactive map. Walter is in charge of designing the plans for long-term imagery acquisition within Europe. Walter sets general goals for areas, deciding which cities and what areas to photograph, and so evaluates use throughout the world. Internationally, he said, it helps us to identify what we call wonders of the world, which we want to cover with high resolution satellite images. We can now make sure we are identifying the right places and also fine tune the actual coverage areas in those places. Walter pointed to Hotmapâ„¢s view of southern Europe (Figure 5), and noted that users had a seeming strong interest in looking at coastlines, including areas where the coast is sparsely populated. A new goal, then, is to make sure we cover not only the cities but all coastlines in decent resolution. While good quality certainly drives viewership, Hotmap allows Walter to compare places with similar coverage. Walter uses Hotmap both to understand how users see both broad worldwide imagery and also how they see individual cities.
In particular, Nicholas is given a prioritized list of cities, and decides which of those cities should be photographed and in what order. Within each city, he is responsible for choosing which areas are to be covered within a strict size budget. Hotmap gives him a cue for where to look when picking the most important areas to cover. In Figure 6 Nicholas pointed to the fact that in addition to the general bright spot over the center of downtown, there are bright spots around several other important areas: (a) Harvard University; (b) Fenway Park, a sports stadium; and © the Bunker Hill monument, an historical site. Nicholas interprets the number of hits”and thus the brightness”as popularity, and so sees these as critical places to acquire further imagery. He also tries to learn usersâ„¢ preferences in well-covered cities so he can generalize to upcoming cities. Nicholas summarized his discoveries as make sure to get the universities, stadiums, and airports. Nicholas then supplements this information with other online and offline sources. Jack is a member of a team that has recently released a mobile application based on the mapping system. Jackâ„¢s team is evaluating the use of their mobile tool, and would like to know where the tool is being adopted. Is it mainly being used to look at American roads, or has it been picked up more broadly around the world? This would help Jackâ„¢s team decide on whether to concentrate on building internationalized versions of the tool rapidly. Jackâ„¢s team provided usage logs from the early deployment of their system to Hotmap.
Nicholas, who is responsible for acquiring city-scale imagery, uses Hotmap differently.
Insights from Hotmap
Insights from Hotmap, found both by teams using the tool and by researchers exploring the data. All the data samples in this section are based on a samplings of tile logs during 2006 and early 2007. Sampling methodologies varied during different stages of deployment, and so numbers of tile hits are relative to each other, and do not directly reflect traffic levels.
4.4 CONSTRUCTING HOTMAP
Hotmap is constructed as an AJAX mash-up over Microsoftâ„¢s Virtual Earth API. The Virtual Earth API includes an ability to superpose translucent tiles from a separate server. Constructing the system as a mash-up has several substantial advantages: as a web , it can be deployed easily; other users can add further data sources over it; and its use can be measured with a server log. Hotmap consists of a server, which serves the around the embedded map; a tile server, which is responsible for returning tile images; and is backed by a database, which stores processed server logs. The input to Hotmap is a sample of Virtual Earth tile server logs. These are trimmed to two core values: a date and a tile identifier. The tile identifier specifies both the location of the tile in space (x, y, and zoom coordinates) and the imagery style of the tile, such as aerial or roads. For performance considerations, the date field is rounded to the nearest day. All tile requests with the same identifier on a given day are aggregated and stored in the database.
5.CONCLUSION
Hotmap is an exploratory data visualization system, which takes advantage of the structure of the underlying data set to visualize it in its own space. In this case, we have examined geospatial imagery, which has the virtue of remaining fixed. When data sets are arranged spatially for users, linking their usage data back can provide important insights into how users approach the data. This is common in eye-tracking studies in which a heatmap is drawn over a web to show where users looked first. There is no set formula for imagery acquisition; thus, allowing users to reflect on the data from a variety of perspectives allows them to understand and explore the dataset in more depth. Hotmap provides a social view of the world, mapping a rough notion of popularity. This social view lets us see where users find the world to be interesting: what parts of it are worth a closer look? This will allow analysts, researchers, and designers to better understand how users interact with their world. Hotmap shows where people have looked at when using Virtual Earth, the engine that powers Live Search Maps: the darker a point, the more times it has been downloaded.
6.REFERENCES
¢ IEEE transactions on visualization and computer graphics, Vol.13,No.6,Novemebr/December 2007. (HotMap : Looking at Geographic Attention)
¢ Information Visualization, 2006. IV 2006. Tenth International Conference on 05-07 July 2006.(The visual Exploration ofWeb Search Results Using HotMap)
¢ labescape.com
¢ maps.live.com
¢ http://code.googleapis/maps/documentation/staticmaps/
¢ http://en.wikipediawiki/AJAX