WP 6 User interface design and implementation. Deliverable 30. GIS query interface specification

Transcription

1 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

2 1 INTRODUCTION IMPLEMENTATION MAP SOURCE GIS APPLICATION GIS FORMULAS TOOLS COLLECTION METADATA GIS PROPOSAL MAP FOR COUNTRY SELECTION STATISTICS UNIT LEVEL METADATA GIS PROPOSAL LOCALISATION OF POINTS ON THE MAP... 8

3 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 ( 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.

4 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

5 = = (source: 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).

6 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.

7 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.

8 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).

9 Fig. 5 A map displaying some dots indicating gathering sites