HTML5 Canvas: An Open Standard for High Performing GIS Map Visualization in Web Browsers. Summary: The evolution of GIS on the Web has, until recently, been limited by traditional Web mapping technologies. The increase in GIS requirements in the Web and mobile world has necessitated the development of a new breed of map engine. This article, by Dino Ravnić, the co-founder and CEO of GIS Cloud, Ltd., provides an overview of existing mapping technologies and the reasons why he decided to build a unique vector mapping engine in an effort to give the Web a full featured GIS.
Introduction: Web GIS - the traditional approach Rendering maps as tiles in raster image format (PNG or JPEG images) is the way geospatial data are commonly delivered on the Web today. This is done by producing tile images on a server and delivering them to a map client. Such technology is used by many Web map providers and it works well for creating nice-looking basemaps like on OpenStreetMap, Google Maps, Bing Maps, etc.
This is all good for Web mapping, but what about GIS? Rendering vectors as vectors. Web mapping client comparison v.6. This comparison aims to serve as a basis for those seeking a first approach to Web mapping technologies at the client side. In the sixth version a number of projects have been added and the whole set of clients has been categorized in order to distinguish them better, since there are currently forty four (44) Web mapping clients in the comparison. Web mapping clients play a significant role in Geoportals of Spatial Data Infrastructures (SDI) allowing the visualization of spatial data from several sources.
Likewise, these clients may be part of Web-based Geographic Information Systems (GIS) applications, in which users can directly interact with SDI services, visualize, query and integrate them with local data and GIS tools. There exists a wide variety of free and open source software (FOSS) projects that make the creation and configuration of Web mapping clients easier. Below is a graph showing the relation between free and open source Web mapping clients. Advantage, Disadvantage. MapTiler - Map Tile Cutter. Overlay Generator for Google Maps, Google Earth (KML SuperOverlay). SidebySide: Google Maps/Bing Maps. Map Compare | Geofabrik Tools. Projections on Bing, Google. I have lately seen several blogposts confused about which datum and projection Microsoft’s Live Maps (Virtual Earth) and Google Maps use.
As most people already know by now, they render the round earth onto a flat screen using a Mercator projection. I think the confusion comes from that they actually use two spatial reference systems at the same time: Geographic Longitude/Latitude coordinatesystem based on the standard WGS84 datum. Mercator projection using a datum based on WGS84, BUT modified to be spheric. So when is what used? The Javascript API’s use (1) as input when you want to add points, lines and polygons.
That is, they expect you to input any geometry in geographical coordinates, and click events etc. will also return geometry in this spatial reference. If you want to create image overlays, or roll your own tile server on top of the map, you will need to project your images into a spheric mercator projection. Here’s a bit of facts about the two projections: