Google Docs for Mobile Devices

From the Google Docs email newsletter:

If you have an iPhone, Blackberry, or Windows Mobile device, now you can point your phone’s browser to http://docs.google.com/m to view read-only, mobile-optimized versions of your docs and spreadsheets. (Your presentations, too, if you have an iPhone; we’ll be making this feature available for other devices shortly.) You might have to squint a little, but now your information will always be right there, in your pocket, wherever you go.

The interface only allows viewing. You cannot edit your documents, spreadsheets or presentations, but just being able to access all my Google Docs is enough for me. I don’t need to edit my documents through my mobile phone - I have a laptop for that.

Show your data on Google map using C# and JavaScript

Almost every one of us who use internet has seen the Google map, Google earth and Google street view etc. Good thing is that Google also share its products in a manner that you can customize them according to your needs. In this article I am going to share a simple technique to show your data on Google map.

Background

Previously I wrote an article on how to count the visits and visitors on your website and save the data in a table including the IPs of the visitors. Then one day I visited a site that was offering to show the similar data on Google map. I started to discover how I can do that if I have a database of IPs. I found that Google share some Maps APIs that offer lot of functionalities including placing a marker on the map if you can provide its coordinate, means the Latitude and longitude of that point on the earth.

Now the only problem was that I had to translate the IP into its corresponding coordinates. I searched again and found some web services on net that can return the coordinate of an IP. That’s all I needed to know to achieve the Goal and now it was just a matter of implementation.

How to do that .. Using the Code

Assuming that you have a table in a database that has two columns for earth coordinates you want to plot on Google map as shown below.

If you have a table that has IPs like in my previous article, you can add two new columns in that table, and then use some web services to update the table for coordinates manually or you can write a small program to call such a web service to update your database automatically. Or may be you want to show your shipments destinations on the map, or you might be interested in showing the location of showrooms of your products around the world and you have a similar data for that. Possibilities are endless.

Now how to plot this data on Google map? Google provides some API methods that you can call in JavaScript from your website and supply the coordinates to place a marker on the map. First you need to add APIs reference in your HTML in header tag as;

<-script src="http://maps.google.com/maps?file=api&v=2&sensor=false&key=abcdefg" type="text/JavaScript"><-/script> 

Note: You need to obtain a unique key for your site from Google before publishing your site. For test purpose on localhost you can use the above code as it’s. Also I am placing a ‘-‘ in every HTLM tag to display on this page, please remove that before running the coed.

Second; you have to place a div element in the page where you want to show the Google map, set its size etc according to your layout needs.

<-div id="map_canvas" style="width: 100%; height: 728px; margin-bottom: 2px;">

Third, you can create a Google map object by passing it div element where you want to show the map.

var map = new GMap2(document.getElementById('map_canvas'));

Also you need to tell what location on the map should be in the center of map, first you get the point from Longitude and Latitude values. For example if you want to see London in the center of the map you can use method as

GLatLng(51.5,-0.1167)

Now you can pass this point to setCenter method with zoom level of your map ranges from 1-20, I am using level 2 to see whole world in my map, increasing this number will zoom the map to your center location.

map.setCenter(new GLatLng(51.5,-0.1167), 2);

Then you can specify a location on the map for Google to place a marker at that location by calling addOverlay method with GMarker object as argument that takes the actual coordinates of the location. For example to place a marker on Toronto, you can call write the following line in script.

map.addOverlay(new GMarker(new GLatLng(43.6667,-79.4168)));

You can specify as many markers as you want. Now you are ready to see the map. Put them all together in a JavaScript function and call it onload event of the page. The complete script will be something like;

<-script type='text/JavaScript'>

function initialize() {

if (GBrowserIsCompatible()) {

var map = new Map2(document.getElementById('map_canvas'));

map.setCenter(new GLatLng(51.5,-0.1167), 2);

map.addOverlay(new Marker(new GLatLng(43.6667,-79.4168)));

map.setUIToDefault();

} } 

But wait a minute.. Java script! Isn’t it client side programming? .. Then how can you pass the data to Google API from a database on your server? Right, this is the problem that you have to deal with. You need to use a combination of JavaScript and any server side scripting e.g. ASP.NET C#, VB, PHP or CGI whichever suites your environment. I used C# and JavaScript to complete this.

You have to generate the JavaScript on the server for Google APIs and render it on the client by using an “asp:Literal” control . You also need to place a Div control on the page in which Google APIs can render a customized map in the browser and add reference to Google APIs script. So you only need two controls on your page a Literal and a Div. The complete HTML is shown below including Google API references for MAP. 

<-html xmlns="http://www.w3.org/1999/xhtml">

<-head id="Head1" runat="server">

<-title>Your Data on Google Map

<-%--Google API reference--%>

<-script src="http://maps.google.com/maps? file=api&v=2&sensor=false&key=abcdefg" type="text/JavaScript">

<-/script>

<-/head>

<-body onload="initialize()" onunload="GUnload()">

<-form id="form1" runat="server">

<-asp:Panel ID="Panel1" runat="server">

<-%--Place holder to fill with JavaScript by server side code--%>

<-asp:Literal ID="js" runat="server">

<-%--Place for Google to show your MAP--%>

<-div id="map_canvas" style="width: 100%; height: 728px; margin-bottom: 2px;">

<-/div>

<-/asp:Panel>

<-/form>

<-/body>

<-/html>

Now how to create the script on server that can show all of your markers on map? Here is a method to do that, you need to pass it the table discussed above that has Longitude and Latitude values in two columns, for the points you want to mark on MAP and this method will generate the complete script with all map markers in the Literal control on the page.

private void BuildScript(DataTable tbl)

{

String Locations = "";

foreach (DataRow r in tbl.Rows)

{

// bypass empty rows

if (r["Latitude"].ToString().Trim().Length == 0)

continue;

string Latitude = r["Latitude"].ToString();

string Longitude = r["Longitude"].ToString();

// create a line of JavaScript for marker on map for this record

Locations += Environment.NewLine + " map.addOverlay(new GMarker(new GLatLng(" + Latitude + "," + Longitude + ")));";

}

// construct the final script

js.Text = @"<-script type='text/JavaScript'>

function initialize() {

if (GBrowserIsCompatible()) {

var map = new GMap2(document.getElementById('map_canvas'));

map.setCenter(new GLatLng(51.5,-0.1167), 2);

" + Locations + @"

map.setUIToDefault();

}

}

<-/script> ";

}

One you call this method in the .cs file of your ASP form, it will create a complete JavaScript for Google to create a map and marker on your page.

Click here to see a live demo of this article. That site shows a marker on map for each location from where any of my sites has been visited. If you have visited any of my sites you should see a marker on your city on the map. Here is a snap of that demo site.

I have created a sample project for this article that you can download by clicking here. It also has a sample access database in it. You can simply run this project in Microsoft Visual Studio 2008 without changing anything.

You can visit Google page about Maps APIs for more details about using and customizing Google Maps.

Google PageRank Defined - Method 1

PageRank is Google’s primary method of ranking web pages in their index. PageRank refers to a hidden value (presumably between 1 and 10) that ranks a page based on importance.

Web pages with higher PageRank (PR for short) are thought (by Google) to be more important, and thus get ranked higher than pages with lower PR.

When one web page links to another web page, they give that page some of their PageRank. This concept is what gives PageRank its power. The theory behind it is this: Let’s say a large, popular website (let’s say CNN.com) links to your web page. The page on their site would likely have a high PR. Google looks at this link to you and gives you a higher PR because they trust CNN.com.

When Google indexes your website, they search for links to your pages, which are called backlinks. The number and quality of backlinks to your website’s pages have a major impact on your PageRank.

Simply put, the more quality links you can get to your website, the higher your website will rank in Google Search.

According to Google, PageRank is:

PageRank reflects our view of the importance of web pages by considering more than 500 million variables and 2 billion terms. Pages that we believe are important pages receive a higher PageRank and are more likely to appear at the top of the search results.
PageRank also considers the importance of each page that casts a vote, as votes from some pages are considered to have greater value, thus giving the linked page greater value. We have always taken a pragmatic approach to help improve search quality and create useful products, and our technology uses the collective intelligence of the web to determine a page’s importance.

How is PageRank calculated? Explained by Google

To calculate the PageRank for a page, all of its inbound links are taken into account. These are links from within the site and links from outside the site.

PR(A) = (1-d) + d(PR(t1)/C(t1) + ... + PR(tn)/C(tn))
 
That's the equation that calculates a page's PageRank. It's the original one that was published when PageRank was being developed, and it is probable that Google uses a variation of it but they aren't telling us what it is. It doesn't matter though, as this equation is good enough.

In the equation 't1 - tn' are pages linking to page A, 'C' is the number of outbound links that a page has and 'd' is a damping factor, usually set to 0.85.

We can think of it in a simpler way:-
a page's PageRank = 0.15 + 0.85 * (a "share" of the PageRank of every page that links to it)
 
"share" = the linking page's PageRank divided by the number of outbound links on the page.
A page "votes" an amount of PageRank onto each page that it links to. The amount of PageRank that it has to vote with is a little less than its own PageRank value (its own value * 0.85). This value is shared equally between all the pages that it links to.

From this, we could conclude that a link from a page with PR4 and 5 outbound links is worth more than a link from a page with PR8 and 100 outbound links. The PageRank of a page that links to yours is important but the number of links on that page is also important. The more links there are on a page, the less PageRank value your page will receive from it.

If the PageRank value differences between PR1, PR2,.....PR10 were equal then that conclusion would hold up, but many people believe that the values between PR1 and PR10 (the maximum) are set on a logarithmic scale, and there is very good reason for believing it. Nobody outside Google knows for sure one way or the other, but the chances are high that the scale is logarithmic, or similar. If so, it means that it takes a lot more additional PageRank for a page to move up to the next PageRank level that it did to move up from the previous PageRank level. The result is that it reverses the previous conclusion, so that a link from a PR8 page that has lots of outbound links is worth more than a link from a PR4 page that has only a few outbound links.
Whichever scale Google uses, we can be sure of one thing. A link from another site increases our site's PageRank. Just remember to avoid links from link farms.

Note that when a page votes its PageRank value to other pages, its own PageRank is not reduced by the value that it is voting. The page doing the voting doesn't give away its PageRank and end up with nothing. It isn't a transfer of PageRank. It is simply a vote according to the page's PageRank value. It's like a shareholders meeting where each shareholder votes according to the number of shares held, but the shares themselves aren't given away. Even so, pages do lose some PageRank indirectly, as we'll see later.
Ok so far? Good. Now we'll look at how the calculations are actually done.

For a page's calculation, its existing PageRank (if it has any) is abandoned completely and a fresh calculation is done where the page relies solely on the PageRank "voted" for it by its current inbound links, which may have changed since the last time the page's PageRank was calculated.

The equation shows clearly how a page's PageRank is arrived at. But what isn't immediately obvious is that it can't work if the calculation is done just once. Suppose we have 2 pages, A and B, which link to each other, and neither have any other links of any kind.

This is what happens:-

Step 1: Calculate page A's PageRank from the value of its inbound links
Page A now has a new PageRank value. The calculation used the value of the inbound link from page B. But page B has an inbound link (from page A) and its new PageRank value hasn't been worked out yet, so page A's new PageRank value is based on inaccurate data and can't be accurate.

Step 2: Calculate page B's PageRank from the value of its inbound links
Page B now has a new PageRank value, but it can't be accurate because the calculation used the new PageRank value of the inbound link from page A, which is inaccurate.

It's a Catch 22 situation. We can't work out A's PageRank until we know B's PageRank, and we can't work out B's PageRank until we know A's PageRank.

Now that both pages have newly calculated PageRank values, can't we just run the calculations again to arrive at accurate values? No. We can run the calculations again using the new values and the results will be more accurate, but we will always be using inaccurate values for the calculations, so the results will always be inaccurate.

The problem is overcome by repeating the calculations many times. Each time produces slightly more accurate values. In fact, total accuracy can never be achieved because the calculations are always based on inaccurate values. 40 to 50 iterations are sufficient to reach a point where any further iterations wouldn't produce enough of a change to the values to matter. This is precisiely what Google does at each update, and it's the reason why the updates take so long.


One thing to bear in mind is that the results we get from the calculations are proportions. The figures must then be set against a scale (known only to Google) to arrive at each page's actual PageRank. Even so, we can use the calculations to channel the PageRank within a site around its pages so that certain pages receive a higher proportion of it than others.


NOTE:
You may come across explanations of PageRank where the same equation is stated but the result of each iteration of the calculation is added to the page's existing PageRank. The new value (result + existing PageRank) is then used when sharing PageRank with other pages. These explanations are wrong for the following reasons:-

1. They quote the same, published equation - but then change it
from PR(A) = (1-d) + d(......) to PR(A) = PR(A) + (1-d) + d(......)
 
It isn't correct, and it isn't necessary.

2. We will be looking at how to organize links so that certain pages end up with a larger proportion of the PageRank than others. Adding to the page's existing PageRank through the iterations produces different proportions than when the equation is used as published. Since the addition is not a part of the published equation, the results are wrong and the proportioning isn't accurate.

According to the published equation, the page being calculated starts from scratch at each iteration. It relies solely on its inbound links. The 'add to the existing PageRank' idea doesn't do that, so its results are necessarily wrong.

What is PageRank? Explained by Google

PageRank is a numeric value that represents how important a page is on the web. Google figures that when one page links to another page, it is effectively casting a vote for the other page. The more votes that are cast for a page, the more important the page must be. Also, the importance of the page that is casting the vote determines how important the vote itself is. Google calculates a page's importance from the votes cast for it. How important each vote is is taken into account when a page's PageRank is calculated.

PageRank is Google's way of deciding a page's importance. It matters because it is one of the factors that determines a page's ranking in the search results. It isn't the only factor that Google uses to rank pages, but it is an important one.

From here on in, we'll occasionally refer to PageRank as "PR".

Notes:

Not all links are counted by Google. For instance, they filter out links from known link farms. Some links can cause a site to be penalized by Google. They rightly figure that webmasters cannot control which sites link to their sites, but they can control which sites they link out to. For this reason, links into a site cannot harm the site, but links from a site can be harmful if they link to penalized sites. So be careful which sites you link to. If a site has PR0, it is usually a penalty, and it would be unwise to link to it.