A BIODIVERSITY COLLECTION ACCESS SERVICE FOR EUROPE
WP 6 – User interface design and implementation
Deliverable 30
GIS query interface specification
Angel Anta
Anna Gadré
Bernard Lepen
Régine Vignes Lebbe
Université Pierre et Marie Curie (Paris 6)
19 December 2003
1
INTRODUCTION............................................................................................................ 3
2
IMPLEMENTATION...................................................................................................... 3
2.1
2.2
2.3
2.4
3
COLLECTION METADATA GIS PROPOSAL.......................................................... 5
3.1
3.2
4
MAP SOURCE ............................................................................................................... 3
GIS APPLICATION ........................................................................................................ 4
GIS FORMULAS ........................................................................................................... 4
TOOLS ......................................................................................................................... 5
MAP FOR COUNTRY SELECTION ................................................................................... 5
STATISTICS .................................................................................................................. 6
UNIT LEVEL METADATA GIS PROPOSAL ............................................................ 8
4.1
LOCALISATION OF POINTS ON THE MAP ....................................................................... 8
1 Introduction
This document is a proposition of GIS–based functionalities to be added to the UI screens,
with the aim to simplify the analysis of the data from the CORM database and from the
multiple databases supplied by the Unit Level Providers.
There are many websites which give a possibility to upload indicated longitude and latitude
coordinates in decimal degrees (or others systems) and create a dynamic map containing dot
plots. Some interfaces for biological data exploration (e.g Fishbase) use this system of map
generation. The maps very often can be customised and directly incorporated into the web
page. But we wish to avoid dependency on external programs or servers because we have no
guarantee that these services will be maintained in the future (may be interrupted or
discontinued at any time without notice). Our goal is the creation of a special BioCASE GIS
module. For all Collection metadata and many Unit Level datasets, the GIS coordinates are
absent or not well structured. For this reason we opted for simple solutions using existing
open source libraries rather than to use professional, expensive GIS software.
2 Implementation
2.1 Map source
The Perry-Castañeda Library Map Collection of the University of Texan of Austin has major
holdings of political, topographic and thematic maps of the world, continents, regions,
countries, states and provinces. A part of the printed map collection has been scanned by the
General Libraries of the University, using an Apple Color One Scanner and a Power
Macintosh G3. The CIA political and shaded relief maps are scanned at 150 dpi. More
detailed maps are scanned at 200 dpi. Images are modified for size and resolution, and
compressed using Adobe Photoshop. The scanned maps are published online in the public
domain on the website (http://www.lib.utexas.edu/maps/index.html) of General Libraries of
the University. No permission is needed to copy, download and transform or use them.
We downloaded the JPG image (Fig. 1) representing a map of Standard Time Zones of the
World 2001.This image can be easily used by a GIS application because all detailed
information necessary for GIS based graphical transformations are procured, especially the
map projection which is Miller Cylindrical Projection.
As this map contains some elements useless for BioCASE users (time zones); it will be
transformed by using GIMP (GNU Image Manipulation Program). A simplified map version
was obtained by tracing the country's boundaries outlines. Next steps consisted to extract a
part of the map representing Europe and including Israel.
Fig. 1 Timezone map of the world
2.2 GIS application
The image of the map consists of adjacent pixels (points) is arranged in rows. The relation
between x and y (the plane coordinates of a projected point on the map) and the geographical
coordinates are given by formulas:
2.3 GIS formulas
The image of the map consists of adjacent pixels (points) is arranged in rows. The relation
between x and y (the plane coordinates of a projected point on the map) and the geographical
coordinates is given by the following formulas:
x
y
=
=
(*)
=
is the longitude of a point on the globe
is central longitude used for the projection
is the latitude of the point on the globe
The inverse equatations are
=
=
(source: http://mathworld.wolfram.com/MillerCylindricalProjection.html)
The calculations were performed with the goal to establish a relations between a pixel
position and the geographic coordinates. The reference points are situated on the Greenwich
Meridian (zero longitude- GMx).
The distance Dpx between two pixels expressed in decimal degrees can be calculated after
measuring the image length (in pixels) and the total longitude interval from the map (in
decimal degrees).
We can calculate x coordinate as [longitude/Dpx] + GMx
x
=
[longitude/Dpx] + GMx
The y coordinate can be calculated using the formula (*).
Some variations, due to the scanning procedure may be observed. The error of precision can
be about 4 pixels of difference of distance between meridians according to their localization
on the map.
2.4 Tools
The graphic libraries GD and the interfaces to Python were used. They can be applied for
quickly drawing images and completed with lines, arcs, text, multiple colors, cut and paste
from other images, and flood fills, and the result written out as a PNG or JPEG file.
3 Collection metadata GIS proposal
3.1 Map for country selection
The most popular method in use today for creating an image with multiple "clickable" areas is
called HTML image map. The list of indicated coordinates of the image is mapped to external
or internal anchors. When the particular zone of image (called also hotspot) is clicked, then
the link is activated.
This method was applied for the input screen representing a selection of the countries. When
the user clicks on the selected country on the map of Europe, the value containing the name of
this country is automatically added to the query criteria (Fig. 2).
Fig. 2 A map for country selection
3.2 Statistics
The datasets and images of the map have been combined into one interactive on-line map
screen that lets the user explore and browse the CORM data.
We analysed the different manners of displaying the set of statistical data representing a
distribution of collections (organisation or networks).
The first, method consists of designing on the map some circles situated in the center of each
country (Fig. 3). The diameter of the circle increases proportionally to the value related to this
country. The disadvantage of this method is related to the fact that certain countries which
have a small area can be masked by the circle allotted to them. The circles can be replaced by
vertical lines with different length but the problem of the overlapping can still arise for closely
situated countries.
Fig. 3 A statistical representation of the distribution of the data as a result of a query in the CORM
datatbase
The retained solution is the color graduaded map (Fig. 4). The numeric values automatically
calculated from the database are grouped infive blocks, each block has a color representation.
The surface of each country is coloured according to the country related value.
The procedure for creating this map consists of the establishment of a list of couples: country
name and associated coordinates of point located on the map (x,y) on the area of this country.
Next, the GD function fillToBorder((x,y), border, color) is used to fill an area surrounded by
a border. All different colors in the area are replaced by the color specified.
Next the map can be rendered clickable. Each country is represented on the map image by one
or more graphical zones . The list of coordinates of all pixels composing each zone is stored
in the goal to be indicated in the HTML MAP tag. An XML file contains an information
about the URL which should be activated when the user clicks on the selected country. Thus,
for example, when the user clicks on any place on the territory of Germany, the screen is
containing an information about the distribution of the German collections, organisations and
networks.
HTML tags: <IMAGE> and related <MAP> dynamically generated in that way can be
directly incorporated into the HTML page.
Fig. 4 A color graduaded representation of the distribution of collections resulting of a query
4 Unit level metadata GIS proposal
4.1 Localisation of points on the map
The ABCD schema contains some elements describing the site coordinates. Three different
systems are proposed:
-Coordinates UTM
-Grid system coordinates
-Latitude and longitude coordinates
Using the calculations described in chapter 2.2 UI can dynamically plot a point on the map of
the world for the couple of indicated coordinates describing the localization of a gathering site
(Fig. 5).
Fig. 5 A map displaying some dots indicating gathering sites