Internet Mapping: Data Management & Transfer Technology Shibu Varghese Daniel Turner Russell Frith

Introduction Web GIS: GIS over the web! Webmap presentation consists of “public visual thinking” and “private visual thinking.” Two distinct areas for evaluation. Read authors’ paper for more details! Literature search reveals volumes of expertise in design considerations for Internet mapping Compare vendors’ implementations using a benchmarking technique. Vendors Compared:

Benchmarking Specification Topics 1.Geospatial Data I/O 2.Communicating Geospatial Data to the Public 3.Webmap Application for “Private Visual Thinking ” Each topic consists of one or more tasks for the evaluation Each topic is accompanied by observations.

Handling Geospatial Data File Formats –Web GIS must have functionality to handle standard GIS file formats –Web GIS software must be able to handle both vector data and raster data (i.e. TIFF) Databases –Web GIS software must be able to handle thematic data by accessing ODBC drivers Map Projection, Coordinate System, and Unit of Measurement –Web GIS software must be able to define map projection, coordinate system, and unit of measurement

Coordinate SystemMiles, Feet, Meters Web GIS Readable Format Geo-referencing Geometry Data Attribute Data Flow Diagram for Task 1: Handling Geospatial Data Task 1 : Handling Geospatial Data

ESRI Shapefile Standard FeatureMust convert to proprietary format via third party tool Must convert to proprietary format via included tool Standard Feature TIFF Standard Feature ODBC Standard Feature Coordinate System/ Georeferencing Does not require any inputs for reference system Reference system designated using Geoset Manager Reference system designated using SDF Loader Reference system designated using separate program Handling Geospatial Data – Observations

Displaying Map Features Web GIS must be able to display and label standard map features relative to scale and category. Polygons (Municipalities vs. Built-up Areas) –Different land areas of cities can be grouped into distinct classes –At large scales, cities represented as polygons –Different classifications imply that polygon map features must be represented using color fills, hatched patterns, a patterned stroke, or some other means of clearly differentiating categories –As scale changes, Web GIS must be able to collapse certain polygon features into points Lines (Transportation Networks) –Interstates, state highways, farm-to-market roadways represent nominal classification. Web GIS software must be able to generate linear map features with different line widths and colors Static Lettering/ Labeling –Labels must not scale when the Web GIS map’s scale is changed –Users/developers must have control over typeface, font size, and font color Generalization –Ensures legibility and correct visual communication of geographic information at every scale of display. –Ensures features resemble actual dimensions of the geometric objects

Flow Diagram for Task 2: Displaying Map Features Web GIS Readable Format Geometry Data Points Lines Polygons Infrastructure Built-up Areas Municipalities VisualizationStatic LetteringGeneralization Webmap Task 2 : Displaying Map Features

Solid/Hatch Fill Allows solid fill; Cannot generate hatched fill Allows for solid fill; Allows for hatched fill Allows for solid fill; Allows for hatched fill Allows for solid fill; Cannot generate hatched fill Color Limited selection of named colors HTML colorsIntegrates color selection from the Windows color palette Font properties Possible to place labels using fonts that are hard to read; size independent of map units; cannot draw boxes around labels Possible to place labels using fonts that are hard to read; size independent of map units; boxes can be drawn around labels Possible to place labels using fonts that are hard to read; size scaled to map units; boxes can be drawn around labels Possible to place labels using fonts that are hard to read; size scaled to map units; cannot draw boxes around labels Text Placement Places labels at the best place. Fixed positioning for labels Allows some control for the positioning of labels Cannot position names on map features Generalization Cannot handle different views for different scales A different map view for each scale interval Cannot handle different views for different scales Road Network Offers a moderate selection of line styles (less than MapGuide, more than Geomedia) Most options for drawing composite lines Fewest options for drawing lines Displaying Map Features – Observations

Displaying Thematic/Attribute Data Web GIS software must be able to generate chorochromatic maps –Each polygon (e.g. city enclosure) must have its own color fill based on something like a nominal classification of a unique variable Web GIS software must be able to generate choropleth maps –Thematic datasets contain statistics about physical environment, population, economics, etc. –Some data sets provide relative values, others offer absolute values –Software must be able to generate proportional symbol maps to represent absolute values and to generate these types of maps to represent the relative values correctly

Geometry Data Attribute Data Classification Nominal Interval Task 3 : Displaying Thematic/Attribute Data Web GIS Readable Format Thematic Webmap Choropleth Map Chorochromatic Map Proportional Symbol Map Qualitative data Quantitative data Flow Diagram for Task 3: Displaying Attribute Data

Classification Selectable classification scheme Does not support classification schemes Does not easily support classification schemes Does not support classification schemes Chorochromatic Map Can be generated using a simple user interface Requires some ASP/VB Script code Chloropleth Map Can be generated using a simple user interface Requires some ASP/VB Script code Proportional Symbol Map Can be generated using a simple user interface Very difficult to generate these kinds of maps Requires some ASP/VB Script code Very difficult to generate these kinds of maps Displaying Thematic Data – Observations

Outputting Hardcopy Maps Web GIS software must allow for printing a specific view of the Web Map, together with the marginal information This requires server-side control over the layout of the document, so users can print maps according to pre-defined layout that assures correct hardcopy map output.

Hardcopy Output May omit scale of legend – requires some programming No standard tools to do this Provides detailed printing; programs allow custom printing Users have little control over the print functions. Output of Hardcopy Maps – Observations

External Identification: Scale, Co-ordinates, and Index Map –Users need to know their location in the geospatial database and where to go –Mouse pointer’s location in map should disclose map co-ordinates –Scale bars should be implemented Internal Identification: Map Legend –Most important interface to the web map –Lists the names of the themes in the map and their cartographic visualization –Must be automatically generated Query Tools –Users need to interact with the Web presentations by asking questions –Users need to know values of variables or what is a particular map element’s properties or statistics. Transferring Geographical Knowledge

Map Scale No means are provided to indicate scale for a thin client. Uses a dialog box to inform the user of the map units in terms of the screen width Client-side scale not provided Automatically displays a scale bar Coordinates Mouse Pointer User clicks on image and screen location converted to map coordinates Does not provide a means to translate mouse position to map coordinates Index Map Standard functionDoes not do this Legend No straightforward means to generate map legend for thin- client. Contains some options to implement a simple, restricted legend. No straightforward means to generate map legend for thin- client. Query Tools Takes too long for users to change view of Webmap to see a particular location Marginal at best. More difficult to use than Arc and MapXtreme. Lack of clickable features makes software unsuitable to develop query tool Transferring Geographical Knowledge – Observations

Thematic datasets contain statistics about various topics. Example: –How many people live in the built-up area of a particular municipality and are within 1/8 mile of an interstate highway assuming 80% of the population of a city lives within the built-up area and assuming that the population is equally distributed within this area? Web GIS software answers this question through answers to a sequence of more specific questions: –What is the name of the city and the interstate hwy on the map? –How large is the distance of 1/8 mi on the Web map? –Make a buffer of 1/8 mi around the highway –What is the area of this buffering surrounding the highway up to 1/8 mi on both sides? –What part of the city intersects this area? –How many people live within this area? Users must be able to measure distances in the Web map between map features. Users must be able to make buffers around map features. Geometric Map Comparison

Task 6 : Geometric Map Comparison Flow Diagram for Task 6: Geometric Map Comparison Measuring Distances Buffering

Measuring Distances Requires extensive scripting. MissingMeasuring tool is a standard. Requires moderate scripting. Buffering Requires extensive scripting MissingBuffer tool is a standard option. Requires extensive scripting. Geometric Map Comparison – Observations

Web maps function as interactive working documents and play important roles in supporting geospatial decision making Joining different geospatial data sets is a common operation for individual research Multiple options of visualization of the same thematic attribute must be enabled by the Web mapping application by means of “re-expression” tools. Since the map is linked to a database, the GIS visualization is altered easily, resulting in a new map type. These “re- expression” tools must facilitate visualization of both relative and absolute values of available datasets to provide correct images of the datasets Clicking an object in a particular view shows its geospatial relations to other objects and representations in all the other views. Web GIS software must be able to add links to map features. Bookmarking must also be supported. Users should be able to hyperlink from one Web document to another. This technique enables additional presentations of text, images, video, etc. Clickable map features must have alternative visualization from non-clickable map features in the same theme and the mouse pointer icon must change as it is placed over a clickable map feature. When users are looking at a particular Web document and want to be able to quickly get back to it later, they should be able to create a bookmark for it. A bookmark should be saved as URL-link w/in the Web browser. Integrating the Web

Add hyperlinkThick clients can add hyperlinks to map features in Webmaps. ClickabilityUsers can only hyperlink after selecting a hyperlink tool; no visual cues that indicate whether a feature is clickable. Serve clickable map features at all times. BookmarkingDoes not support.Difficult to do. Requires considerable scripting. Only package to offer client-side bookmarking. Does not support. Integrating the Web – Observations

Conclusions Autodesk MapGuide appears to offer the most functionality of all the tools. ArcIMS is the best tool at displaying thematic data and for transferring geographical knowledge. Autodesk supports the best tools for displaying map features. Autodesk has the best hardcopy function. Autodesk is the best at geometric map comparison. Autodesk is the best at integrating with the Web. Autodesk is the best tool for most kinds of analysis involving database queries and report generation. ArcIMS is the best tool for public (thematic) presentation of maps!