spatialepidemiology.net

To aid in the exploitation of facilities such as Google maps for epidemiological purposes we provide map creation tools allowing you to enter your own data and create a permanent map (which can be bookmarked or sent to others via email).  

Many will be unfamiliar or not have access to latitude / longitude values for the points to be plotted on a map.  We therefore provide two interfaces to geocoding facilities thatallow you to find map co-ordinates. 

Each point on the map is represented by a set of data which, at its most basic, includes the name given to the point, the latitude and longitude values that define the point geographically and a description of the point that appears in a ‘pop-up’ window when the map icon is clicked on.

To produce a map, data are pasted into the map creation pages in TAB delimited format.  It is important to have the data in the correct format and to simplify this procedure we provide excel templates for entering and storing your data.

We demonstrate the use of the tools with some test data

• 1) Geocoding
• 2) Simple map creation
• 3) Advanced map creation

Should you be unfamiliar with latitude / longitudes that are needed to build the map, we provide geocoding webpages that take advantage of Googles Geocoding Web Service.  You can geocode by eye using the Map lat/lon lookup  or paste in lists of addresses and have the latitude and longitude (and associated spatial resolution) returned enabling you to build up data to enter into the map creation tools.

Initially you are presented with a zoomed out view of the world.  By clicking/dragging and zooming in you can find the location you wish to Geocode.  By clicking on the map an icon appears and the latitude / longitude is displayed in the pop-up window.   For convenience, below the map the latitude and longitude are also displayed in text boxes which means that you can copy and paste elsewhere.   There is also a link to multimap.com with the point that you have geocoded so you can double check that your point is correct.

This facility allows you to paste multiple addresses into a form, each one is then looked up using Googles geocoding facility and the resulting latitude / longitude (if found) are returned.

You can paste addresses in comma or tab delimited formats
For example  New York,USA  or New York USA
The geocoder works at many levels of resolution from street address or postal code (UK) or Zip (US)

e.g    “10 Downing Street, London” or “The Thite House, Washington DC, USA ”

up to country level

e.g.  Brazil.   

For countries, capital cities or districts, the centroid point for that region is returned.

The results returned from the geocoder consist of six columns  as follows : -

Address | Latitude | Longitude | Accuracy | Number of Addresses Returned | Address or error code.

As an example,  by entering “London,UK”  the following results are returned –

london,uk         51.500152       -0.126236        4          1          London, Greater London, UK

The first column is the ‘Address’ that you typed in.
The second column is the latitude
The third column is the longitude
The fourth column is the Accuracy.

Accuracy is an integer returned from Google as follows –

For further details please see here – (http://googlemapsapi.blogspot.com/2006/07/speed-improvements-custom-cursors.html)

In our example the accuracy is “4”.  This signifies that the geocoding is accurate to the Town (City, Village) level which would be expected for London.

The fifth column contains the Number of addresses returned.  

This is "1" for London, UK  because there is only one matching location for London in the UK.

If however we geocode London,USA  more results are returned as follows- 

london,usa        37.125766       -84.07986      4          8          London, KY, USA
london,usa        39.895163       -83.440461     4          8          London, OH, USA
london,usa        35.330799       -93.247163     4          8          London, AR, USA
london,usa        47.20278        -91.56944      4          8          London, MN, USA
london,usa        40.445          -95.23472      4          8          London, MO, USA
london,usa        37.119612       -84.089603     4          8          London, KY, USA
london,usa        36.488426       -119.448791    4          8          London, CA, USA
london,usa        39.890448       -83.434486     4          8          London, OH, USA

this shows there are 8 (as in the fifth column) matches to London,USA
.
In this circumstance it is important to check which address is the one you are interested in using.

The final column contains the address as stored by Google, which may be more descriptive than the address you entered.

Points to note –
If a result is not returned for your address it may be that it is not possible to geocode or it may be that you need to format the query address better.  It is best to include as much information as possible.

The simple map tool allows you to plot a list of geocoded locations on a map that you can save as a permanent URL (webpage).

Any number of points can be plotted and the map and example data should give you some indication of the kind of simple map that can be produced. 

First, enter a title - this will be displayed on the resulting map

Name represents the name you have given to your point e.g., a hospital
latitude is the latitude of the point
longitude is the longitude of the point
description is the description you wish to give the data point on the map.

The Advanced map tool allows you to group your data into meaningful categories and colour the placemarks of each group differently. This could be applied for example to population figures, presence or severity of a disease etc.

PLEASE NOTE: we will shortly be making available a much improved version of the Advanced map tool that allows user defined keys and grouping of more than one set of data at a single datapoint (for further info please contact us).

Any number of points can be plotted and the map and the example data provided should give you some indication of the kind of map that can be produced. 

Name represents the name you have given to your point e.g a hospital
latitude is the latitude of the point
longitude is the longitude of the point
description is any description you wish to give to the data point.
ICON represents the choice of ICON for that point based on the KEY given.

The choice of icon can be used to group your data into defined categories (e.g. they could be ranges (<1%, 1-5%, 6-10% etc) that show the prevalance of drug-resistant malaria parasites).